Zinc oxide

Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement, lubricants, paints, sunscreens, ointments, adhesives, sealants, pigments, foods, batteries, ferrites, fire retardants, semi conductors, and first-aid tapes. Although it occurs naturally as the mineral zincite, most zinc oxide is produced synthetically.

## History

Zinc compounds were probably used by early humans, in processed and unprocessed forms, as a paint or medicinal ointment, but their composition is uncertain. The use of pushpanjan, probably zinc oxide, as a salve for eyes and open wounds, is mentioned in the Indian medical text the Charaka Samhita, thought to date from 500 BC or before. Zinc oxide ointment is also mentioned by the Greek physician Dioscorides (1st century AD). Galen suggested treating ulcerating cancers with zinc oxide, as did Avicenna in his The Canon of Medicine. It is used as an ingredient in products such as baby powder and creams against diaper rashes, calamine cream, anti-dandruff shampoos, and antiseptic ointments.

The Romans produced considerable quantities of brass (an alloy of zinc and copper) as early as 200 BC by a cementation process where copper was reacted with zinc oxide. The zinc oxide is thought to have been produced by heating zinc ore in a shaft furnace. This liberated metallic zinc as a vapor, which then ascended the flue and condensed as the oxide. This process was described by Dioscorides in the 1st century AD. Zinc oxide has also been recovered from zinc mines at Zawar in India, dating from the second half of the first millennium BC.

From the 12th to the 16th century zinc and zinc oxide were recognized and produced in India using a primitive form of the direct synthesis process. From India, zinc manufacture moved to China in the 17th century. In 1743, the first European zinc smelter was established in Bristol, United Kingdom. Around 1782 Louis-Bernard Guyton de Morveau proposed replacing lead white pigment with zinc oxide.

The main usage of zinc oxide (zinc white) was in paints and as an additive to ointments. Zinc white was accepted as a pigment in oil paintings by 1834 but it did not mix well with oil. This problem was solved by optimizing the synthesis of ZnO. In 1845, Edme-Jean Leclaire in Paris was producing the oil paint on a large scale, and by 1850, zinc white was being manufactured throughout Europe. The success of zinc white paint was due to its advantages over the traditional white lead: zinc white is essentially permanent in sunlight, it is not blackened by sulfur-bearing air, it is non-toxic and more economical. Because zinc white is so "clean" it is valuable for making tints with other colors, but it makes a rather brittle dry film when unmixed with other colors. For example, during the late 1890s and early 1900s, some artists used zinc white as a ground for their oil paintings. All those paintings developed cracks over the years.

In recent times, most zinc oxide was used in the rubber industry to resist corrosion. In the 1970s, the second largest application of ZnO was photocopying. High-quality ZnO produced by the "French process" was added to photocopying paper as a filler. This application was soon displaced by titanium.

## Chemical properties

Pure ZnO is a white powder, but in nature it occurs as the rare mineral zincite, which usually contains manganese and other impurities that confer a yellow to red color.

Crystalline zinc oxide is thermochromic, changing from white to yellow when heated in air and reverting to white on cooling. This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x = 0.00007.

Zinc oxide is an amphoteric oxide. It is nearly insoluble in water, but it will dissolve in most acids, such as hydrochloric acid:

ZnO + 2 HCl → ZnCl2 + H2O

Solid zinc oxide will also dissolve in alkalis to give soluble zincates:

ZnO + 2 NaOH + H2O → Na2[Zn(OH)4]

ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate. When mixed with a strong aqueous solution of zinc chloride, ZnO forms cement-like products best described as zinc hydroxy chlorides. This cement was used in dentistry.

ZnO also forms cement-like material when treated with phosphoric acid; related materials are used in dentistry. A major component of zinc phosphate cement produced by this reaction is hopeite, Zn3(PO4)2·4H2O.

ZnO decomposes into zinc vapor and oxygen at around 1975 °C with a standard oxygen pressure. In a carbothermic reaction, heating with carbon converts the oxide into zinc vapor at a much lower temperature (around 950 °C).

ZnO + C → Zn(Vapor) + CO

## Physical properties

### Structure

Zinc oxide crystallizes in two main forms, hexagonal wurtzite and cubic zincblende. The wurtzite structure is most stable at ambient conditions and thus most common. The zincblende form can be stabilized by growing ZnO on substrates with cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral, the most characteristic geometry for Zn(II). ZnO converts to the rocksalt motif at relatively high pressures about 10 GPa. The many remarkable medical properties of creams containing ZnO can be explained by its elastic softness, which is characteristic of tetrahedral coordinated binary compounds close to the transition to octahedral structures.

Hexagonal and zincblende polymorphs have no inversion symmetry (reflection of a crystal relative to any given point does not transform it into itself). This and other lattice symmetry properties result in piezoelectricity of the hexagonal and zincblende ZnO, and pyroelectricity of hexagonal ZnO.

The hexagonal structure has a point group 6 mm (Hermann–Mauguin notation) or C6v (Schoenflies notation), and the space group is P63mc or C6v4. The lattice constants are a = 3.25 Å and c = 5.2 Å; their ratio c/a \~ 1.60 is close to the ideal value for hexagonal cell c/a = 1.633. As in most group II-VI materials, the bonding in ZnO is largely ionic (Zn2+O2−) with the corresponding radii of 0.074 nm for Zn2+ and 0.140 nm for O2−. This property accounts for the preferential formation of wurtzite rather than zinc blende structure, as well as the strong piezoelectricity of ZnO. Because of the polar Zn−O bonds, zinc and oxygen planes are electrically charged. To maintain electrical neutrality, those planes reconstruct at atomic level in most relative materials, but not in ZnO – its surfaces are atomically flat, stable and exhibit no reconstruction. However, studies using wurtzoid structures explained the origin of surface flatness and the absence of reconstruction at ZnO wurtzite surfaces in addition to the origin of charges on ZnO planes.

### Mechanical properties

ZnO is a wide-band gap semiconductor of the II-VI semiconductor group. The native doping of the semiconductor due to oxygen vacancies or zinc interstitials is n-type.

ZnO is a relatively soft material with approximate hardness of 4.5 on the Mohs scale. Its elastic constants are smaller than those of relevant III-V semiconductors, such as GaN. The high heat capacity and heat conductivity, low thermal expansion and high melting temperature of ZnO are beneficial for ceramics. The E2 optical phonon in ZnO exhibits an unusually long lifetime of 133 ps at 10 K.

Among the tetrahedrally bonded semiconductors, it has been stated that ZnO has the highest piezoelectric tensor, or at least one comparable to that of GaN and AlN. This property makes it a technologically important material for many piezoelectrical applications, which require a large electromechanical coupling. Therefore, ZnO in the form of thin film has been one of the most studied resonator materials for thin-film bulk acoustic resonators.

### Electrical and optical properties

Favourable properties of zinc oxide include good transparency, high electron mobility, wide band gap, and strong room-temperature luminescence. Those properties make ZnO valuable for a variety of emerging applications: transparent electrodes in liquid crystal displays, energy-saving or heat-protecting windows, and electronics as thin-film transistors and light-emitting diodes.

ZnO has a relatively wide direct band gap of \~3.3 eV at room temperature. Advantages associated with a wide band gap include higher breakdown voltages, ability to sustain large electric fields, lower electronic noise, and high-temperature and high-power operation. The band gap of ZnO can further be tuned to \~3–4 eV by its alloying with magnesium oxide or cadmium oxide.

Most ZnO has n-type character, even in the absence of intentional doping. Nonstoichiometry is typically the origin of n-type character, but the subject remains controversial. An alternative explanation has been proposed, based on theoretical calculations, that unintentional substitutional hydrogen impurities are responsible. Controllable n-type doping is easily achieved by substituting Zn with group-III elements such as Al, Ga, In or by substituting oxygen with group-VII elements chlorine or iodine.

Reliable p-type doping of ZnO remains difficult. This problem originates from low solubility of p-type dopants and their compensation by abundant n-type impurities. This problem is observed with GaN and ZnSe. Measurement of p-type in "intrinsically" n-type material is complicated by the inhomogeneity of samples.

Current limitations to p-doping limit electronic and optoelectronic applications of ZnO, which usually require junctions of n-type and p-type material. Known p-type dopants include group-I elements Li, Na, K; group-V elements N, P and As; as well as copper and silver. However, many of these form deep acceptors and do not produce significant p-type conduction at room temperature.

Electron mobility of ZnO strongly varies with temperature and has a maximum of \~2000 cm2/(V·s) at 80 K. Data on hole mobility are scarce with values in the range 5–30 cm2/(V·s).

ZnO discs, acting as a varistor, are the active material in most surge arresters.

Zinc oxide is noted for its strongly nonlinear optical properties, especially in bulk. The nonlinearity of ZnO nanoparticles can be fine-tuned according to their size.

## Production

For industrial use, ZnO is produced at levels of 105 tons per year by three main processes:

### Indirect process

In the indirect or French process, metallic zinc is melted in a graphite crucible and vaporized at temperatures above 907 °C (typically around 1000 °C). Zinc vapor reacts with the oxygen in the air to give ZnO, accompanied by a drop in its temperature and bright luminescence. Zinc oxide particles are transported into a cooling duct and collected in a bag house. This indirect method was popularized by Edme Jean LeClaire of Paris in 1844 and therefore is commonly known as the French process. Its product normally consists of agglomerated zinc oxide particles with an average size of 0.1 to a few micrometers. By weight, most of the world's zinc oxide is manufactured via French process.

### Direct process

The direct or American process starts with diverse contaminated zinc composites, such as zinc ores or smelter by-products. The zinc precursors are reduced (carbothermal reduction) by heating with a source of carbon such as anthracite to produce zinc vapor, which is then oxidized as in the indirect process. Because of the lower purity of the source material, the final product is also of lower quality in the direct process as compared to the indirect one.

### Wet chemical process

A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated. The solid precipitate is then calcined at temperatures around 800 °C.

### Laboratory synthesis

Numerous specialised methods exist for producing ZnO for scientific studies and niche applications. These methods can be classified by the resulting ZnO form (bulk, thin film, nanowire), temperature ("low", that is close to room temperature or "high", that is T \~ 1000 °C), process type (vapor deposition or growth from solution) and other parameters.

Large single crystals (many cubic centimeters) can be grown by the gas transport (vapor-phase deposition), hydrothermal synthesis, or melt growth. However, because of the high vapor pressure of ZnO, growth from the melt is problematic. Growth by gas transport is difficult to control, leaving the hydrothermal method as a preference. Thin films can be produced by chemical vapor deposition, metalorganic vapour phase epitaxy, electrodeposition, pulsed laser deposition, sputtering, sol–gel synthesis, atomic layer deposition, spray pyrolysis, etc.

Ordinary white powdered zinc oxide can be produced in the laboratory by electrolyzing a solution of sodium bicarbonate with a zinc anode. Zinc hydroxide and hydrogen gas are produced. The zinc hydroxide upon heating decomposes to zinc oxide:

Zn + 2 H2O → Zn(OH)2 + H2

Zn(OH)2 → ZnO + H2O

### ZnO nanostructures

Nanostructures of ZnO can be synthesized into a variety of morphologies including nanowires, nanorods, tetrapods, nanobelts, nanoflowers, nanoparticles etc. Nanostructures can be obtained with most above-mentioned techniques, at certain conditions, and also with the vapor–liquid–solid method. The synthesis is typically carried out at temperatures of about 90 °C, in an equimolar aqueous solution of zinc nitrate and hexamine, the latter providing the basic environment. Certain additives, such as polyethylene glycol or polyethylenimine, can improve the aspect ratio of the ZnO nanowires. Doping of the ZnO nanowires has been achieved by adding other metal nitrates to the growth solution. The morphology of the resulting nanostructures can be tuned by changing the parameters relating to the precursor composition (such as the zinc concentration and pH) or to the thermal treatment (such as the temperature and heating rate).

Aligned ZnO nanowires on pre-seeded silicon, glass, and gallium nitride substrates have been grown using aqueous zinc salts such as zinc nitrate and zinc acetate in basic environments. Pre-seeding substrates with ZnO creates sites for homogeneous nucleation of ZnO crystal during the synthesis. Common pre-seeding methods include in-situ thermal decomposition of zinc acetate crystallites, spincoating of ZnO nanoparticles and the use of physical vapor deposition methods to deposit ZnO thin films. Pre-seeding can be performed in conjunction with top down patterning methods such as electron beam lithography and nanosphere lithography to designate nucleation sites prior to growth. Aligned ZnO nanowires can be used in dye-sensitized solar cells and field emission devices.

## Applications

The applications of zinc oxide powder are numerous, and the principal ones are summarized below. Most applications exploit the reactivity of the oxide as a precursor to other zinc compounds. For material science applications, zinc oxide has high refractive index, high thermal conductivity, binding, antibacterial and UV-protection properties. Consequently, it is added into materials and products including plastics, ceramics, glass, cement, rubber, lubricants, paints, ointments, adhesive, sealants, concrete manufacturing, pigments, foods, batteries, ferrites, fire retardants, etc.

### Rubber industry

Between 50% and 60% of ZnO use is in the rubber industry. Zinc oxide along with stearic acid is used in the sulfur vulcanization of rubber. ZnO additives also protect rubber from fungi (see medical applications) and UV light.

### Ceramic industry

Ceramic industry consumes a significant amount of zinc oxide, in particular in ceramic glaze and frit compositions. The relatively high heat capacity, thermal conductivity and high temperature stability of ZnO coupled with a comparatively low coefficient of expansion are desirable properties in the production of ceramics. ZnO affects the melting point and optical properties of the glazes, enamels, and ceramic formulations. Zinc oxide as a low expansion, secondary flux improves the elasticity of glazes by reducing the change in viscosity as a function of temperature and helps prevent crazing and shivering. By substituting ZnO for BaO and PbO, the heat capacity is decreased and the thermal conductivity is increased. Zinc in small amounts improves the development of glossy and brilliant surfaces. However, in moderate to high amounts, it produces matte and crystalline surfaces. With regard to color, zinc has a complicated influence.

### Medicine

Zinc oxide as a mixture with about 0.5% iron(III) oxide (Fe2O3) is called calamine and is used in calamine lotion. Historically the mineral calamine is a mixture of the oxides zincite and hemimorphite. When mixed with eugenol, zinc oxide eugenol is formed, which has applications as a restorative and prosthodontic in dentistry.

Powdered zinc oxide has deodorizing and antibacterial properties. ZnO is added to cotton fabric, rubber, oral care products, and food packaging. Enhanced antibacterial action of fine particles compared to bulk material is not exclusive to ZnO and is observed for other materials, such as silver. This property results from the increased surface area of the fine particles.

Zinc oxide is used in mouthwash products and toothpastes as an anti-bacterial agent proposed to prevent plaque and tartar formation, and to control bad breath by reducing the volatile gases and volatile sulfur compounds (VSC) in the mouth. Along with zinc oxide or zinc salts, these products also commonly contain other active ingredients, such as cetylpyridinium chloride, xylitol, hinokitiol, essential oils and plant extracts.

Zinc oxide is widely used to treat a variety of skin conditions, including atopic dermatitis, contact dermatitis, itching due to eczema, diaper rash and acne. It is used in products such as baby powder and barrier creams to treat diaper rashes, calamine cream, anti-dandruff shampoos, and antiseptic ointments. It is often combined with castor oil to form an emollient and astringent, zinc and castor oil cream, commonly used to treat infants.

It is also a component in tape (called "zinc oxide tape") used by athletes as a bandage to prevent soft tissue damage during workouts. Zinc oxide is also often added into sunscreens.

Zinc oxide can be used in ointments, creams, and lotions to protect against sunburn and other damage to the skin caused by ultraviolet light (see sunscreen). It is the broadest spectrum UVA and UVB absorber that is approved for use as a sunscreen by the U.S. Food and Drug Administration (FDA), and is completely photostable. When used as an ingredient in sunscreen, zinc oxide blocks both UVA (320–400 nm) and UVB (280–320 nm) rays of ultraviolet light. Zinc oxide and the other most common physical sunscreen, titanium dioxide, are considered to be nonirritating, nonallergenic, and non-comedogenic. Zinc from zinc oxide is, however, slightly absorbed into the skin.

Many sunscreens use nanoparticles of zinc oxide (along with nanoparticles of titanium dioxide) because such small particles do not scatter light and therefore do not appear white. The nanoparticles are not absorbed into the skin more than regular-sized zinc oxide particles are, and are only absorbed into the outermost layer of the skin but not into the body.

### Food additive

Zinc oxide is added to many food products, including breakfast cereals, as a source of zinc, a necessary nutrient. Zinc sulfate is also used for the same purpose. Some prepackaged foods also include trace amounts of ZnO even if it is not intended as a nutrient.

### Pigment

Zinc oxide (zinc white) is used as a pigment in paints and is more opaque than lithopone, but less opaque than titanium dioxide. It is also used in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. The use of zinc white as a pigment in oil painting started in the middle of 18th century. It has partly replaced the poisonous lead white and was used by painters such as Böcklin, Van Gogh, Manet, Munch and others. It is also a main ingredient of mineral makeup (CI 77947).

### UV absorber

Micronized and nano-scale zinc oxide provides strong protection against UVA and UVB ultraviolet radiation, and are consequently used in sunscreens, and also in UV-blocking sunglasses for use in space and for protection when welding, following research by scientists at Jet Propulsion Laboratory (JPL).

### Coatings

Paints containing zinc oxide powder have long been utilized as anticorrosive coatings for metals. They are especially effective for galvanized iron. Iron is difficult to protect because its reactivity with organic coatings leads to brittleness and lack of adhesion. Zinc oxide paints retain their flexibility and adherence on such surfaces for many years.

ZnO highly n-type doped with aluminium, gallium, or indium is transparent and conductive (transparency \~90%, lowest resistivity \~10−4 Ω·cm). ZnO:Al coatings are used for energy-saving or heat-protecting windows. The coating lets the visible part of the spectrum in but either reflects the infrared (IR) radiation back into the room (energy saving) or does not let the IR radiation into the room (heat protection), depending on which side of the window has the coating.

Plastics, such as polyethylene naphthalate (PEN), can be protected by applying zinc oxide coating. The coating reduces the diffusion of oxygen through PEN. Zinc oxide layers can also be used on polycarbonate in outdoor applications. The coating protects polycarbonate from solar radiation, and decreases its oxidation rate and photo-yellowing.

### Corrosion prevention in nuclear reactors

Zinc oxide depleted in 64Zn (the zinc isotope with atomic mass 64) is used in corrosion prevention in nuclear pressurized water reactors. The depletion is necessary, because 64Zn is transformed into radioactive 65Zn under irradiation by the reactor neutrons.

### Methane reforming

Zinc oxide (ZnO) is used as a pretreatment step to remove hydrogen sulfide (H2S) from natural gas following hydrogenation of any sulfur compounds prior to a methane reformer, which can poison the catalyst. At temperatures between about 230–430 °C (446–806 °F), H2S is converted to water by the following reaction:

H2S + ZnO → H2O + ZnS

### Electronics

ZnO has wide direct band gap (3.37 eV or 375 nm at room temperature). Therefore, its most common potential applications are in laser diodes and light emitting diodes (LEDs). Moreover, ultrafast nonlinearities and photoconductive functions have been reported in ZnO. Some optoelectronic applications of ZnO overlap with that of GaN, which has a similar band gap (\~3.4 eV at room temperature). Compared to GaN, ZnO has a larger exciton binding energy (\~60 meV, 2.4 times of the room-temperature thermal energy), which results in bright room-temperature emission from ZnO. ZnO can be combined with GaN for LED-applications. For instance, a transparent conducting oxide layer and ZnO nanostructures provide better light outcoupling. Other properties of ZnO favorable for electronic applications include its stability to high-energy radiation and its ability to be patterned by wet chemical etching. Radiation resistance makes ZnO a suitable candidate for space applications. ZnO is the most promising candidate in the field of random lasers to produce an electronically pumped UV laser source.

The pointed tips of ZnO nanorods result in a strong enhancement of an electric field. Therefore, they can be used as field emitters.

Aluminium-doped ZnO layers are used as transparent electrodes. The components Zn and Al are much cheaper and less toxic compared to the generally used indium tin oxide (ITO). One application which has begun to be commercially available is the use of ZnO as the front contact for solar cells or of liquid crystal displays.

Transparent thin-film transistors (TTFT) can be produced with ZnO. As field-effect transistors, they do not need a p–n junction, thus avoiding the p-type doping problem of ZnO. Some of the field-effect transistors even use ZnO nanorods as conducting channels.

### Zinc oxide nanorod sensor

Zinc oxide nanorod sensors are devices detecting changes in electric current passing through zinc oxide nanowires due to adsorption of gas molecules. Selectivity to hydrogen gas was achieved by sputtering palladium clusters on the nanorod surface. The addition of palladium appears to be effective in the catalytic dissociation of hydrogen molecules into atomic hydrogen, increasing the sensitivity of the sensor device. The sensor detects hydrogen concentrations down to 10 parts per million at room temperature, whereas there is no response to oxygen. ZnO have been used as immobilization layers in immunosensors enabling the distribution of antibodies across the entire region probed by the measuring electric field applied to the microelectrodes.

### Piezoelectricity

The piezoelectricity in textile fibers coated in ZnO have been shown capable of fabricating "self-powered nanosystems" with everyday mechanical stress from wind or body movements.

In 2008 the Center for Nanostructure Characterization at the Georgia Institute of Technology reported producing an electricity generating device (called flexible charge pump generator) delivering alternating current by stretching and releasing zinc oxide nanowires. This mini-generator creates an oscillating voltage up to 45 millivolts, converting close to seven percent of the applied mechanical energy into electricity. Researchers used wires with lengths of 0.2–0.3 mm and diameters of three to five micrometers, but the device could be scaled down to smaller size.

In form of a thin film ZnO has been demonstrated in miniaturised high frequency thin film resonators, sensors and filters.

### Li-ion battery and supercapacitors

ZnO is a promising anode material for lithium-ion battery because it is cheap, biocompatible, and environmentally friendly. ZnO has a higher theoretical capacity (978 mAh g−1) than many other transition metal oxides such as CoO (715 mAh g−1), NiO (718 mAh g−1) and CuO (674 mAh g−1). ZnO is also used as an electrode in supercapacitors.

## Safety

As a food additive, zinc oxide is on the U.S. FDA's list of generally recognized as safe, or GRAS, substances.

Zinc oxide itself is non-toxic; it is hazardous, however, to inhale zinc oxide fumes, such as generated when zinc or zinc alloys are melted and oxidized at high temperature. This problem occurs while melting alloys containing brass because the melting point of brass is close to the boiling point of zinc. Exposure to zinc oxide in the air, which also occurs while welding galvanized (zinc plated) steel, can result in a malady called metal fume fever. For this reason, typically galvanized steel is not welded, or the zinc is removed first.

In sunscreen, formulations that combined zinc oxide with other petrochemical UV absorbers, it was found that zinc oxide caused the photodegradation of small-molecule petrochemical UV absorbers, which exhibited toxicity in embryonic zebrafish assays.

## See also

- Depleted zinc oxide
- Zinc oxide nanoparticle
- Gallium(III) nitride
- List of inorganic pigments
- Zinc
- Zinc oxide eugenol
- Zinc peroxide
- Zinc smelting
- Zinc–air battery
- Zinc–zinc oxide cycle
- ZnO nanostructures

## Cited sources

## Reviews

White powder insoluble in water


2005 Atlantic hurricane season

The 2005 Atlantic hurricane season was the second-most active Atlantic hurricane season in history, with it being the most active until the record was broken 15 years later in 2020. The season broke numerous records at the time, with 28 tropical or subtropical storms recorded. The United States National Hurricane Center named 27 storms, exhausting the annual pre-designated list and resulting in the usage of six Greek letter names, and also identified an additional unnamed storm during a post-season re-analysis. A record 15 storms attained hurricane status, with maximum sustained winds of at least 74 miles per hour (119 km/h); of those, a record seven became major hurricanes, which are a Category 3 or higher on the Saffir–Simpson scale. Four storms of this season became Category 5 hurricanes, the highest ranking on the scale.

The four Category 5 hurricanes that developed during the season were: Emily, Katrina, Rita, and Wilma. In July, Emily reached peak intensity in the Caribbean Sea, becoming the first Category 5 hurricane of the season, later weakening and striking Mexico twice. In August, Katrina reached peak winds in the Gulf of Mexico but weakened by the time it struck the U.S. states of Louisiana and Mississippi. The most devastating effects of the season were felt on the Gulf Coast of the United States, where Katrina's storm surge crippled New Orleans, Louisiana, for weeks and devastated the Mississippi coastline. Katrina became the costliest U.S. hurricane, leaving \$125 billion in damage and 1,392 deaths. Rita followed in September, reaching peak intensity in the Gulf of Mexico before weakening and hitting near the border of Texas and Louisiana. The season's strongest hurricane, Wilma, became the most intense Atlantic hurricane on record, as measured by barometric pressure. Lasting for ten days in October, Wilma moved over Cozumel, the Yucatán Peninsula, and Florida, causing over \$22 billion in damage and 52 deaths.

The season's impact was widespread and catastrophic. Its storms caused an estimated 3,468 deaths and approximately \$172.3 billion in damage. It was the costliest season on record at the time, until its record was surpassed 12 years later. It also produced the second-highest accumulated cyclone energy (ACE) in the Atlantic basin, surpassed only by the 1933 season. The season officially began on June 1, 2005, and the first storm – Arlene – developed on June 8. Hurricane Dennis in July inflicted heavy damage to Cuba. Hurricane Stan in October was part of a broader weather system that killed 1,668 people and caused \$3.96 billion in damage to eastern Mexico and Central America, with Guatemala hit the hardest. The final storm – Zeta – formed in late December and lasted until January 6, 2006.

## Seasonal forecasts

Ahead of the formal start of the season, various groups issued forecasts for the number of named storms, hurricanes, and major hurricanes in the upcoming season, including Colorado State University (CSU), the Cuban Institute of Meteorology (InsMet), Tropical Storm Risk (TSR), and the United States National Oceanic and Atmospheric Administration (NOAA). Some forecasts predicted how many tropical cyclones would affect a particular country or territory.

### Pre-season forecasts

The first of these forecasts was issued by CSU, which predicted on December 5, 2004 that the season would be above average and feature 11 named storms, 6 hurricanes and 3 intense hurricanes. They also noted that the Caribbean and the entire United States coastline faced an increased risk of a major hurricane making landfall. TSR issued its first forecast a few days later and predicted that the season would feature 9.6 tropical storms, 5.7 hurricanes, 3.3 major hurricanes, and predicted that the accumulated cyclone energy (ACE) rating would be 145.

During January 2005, TSR increased its forecast to 13.9 tropical storms, 7.8 hurricanes, 3.6 major hurricanes, and predicted that the ACE rating would be 157. CSU issued its first updated forecast on April 1, increasing their prediction to 13 tropical storms, 7 hurricanes, and 3 major hurricanes, with a continued risk of a major hurricane landfall in the Caribbean or United States. The increase was based on the Atlantic continuing to warm and a strong belief that El Niño conditions would not persist into the hurricane season. On May 2, the Cuban Institute of Meteorology (InsMet) issued their seasonal forecast, which predicted that the season would feature 13 tropical storms and 7 hurricanes. This was followed on May 16 by NOAA, who predicted a 70% chance of above normal activity, with 12–15 tropical storms, 7–9 hurricanes, and 3–5 major hurricanes. CSU issued its second forecast update on May 31, revising its forecast to 15 named storms, 8 hurricanes and 4 major hurricanes; by this point, the group believed El Niño conditions were unlikely.

### Midseason outlooks

In their July forecast update, TSR anticipated that the season would be exceptionally active and well above average; the group increased their forecast to 15.3 tropical storms, 8.8 hurricanes, and 4.1 major hurricanes, with an ACE rating of 190. By the end of July, seven tropical storms and two major hurricanes had developed within the basin, which prompted CSU, InsMet, NOAA and TSR to significantly increase their seasonal forecasts at the start of August. In their August 5 update, CSU predicted that 13 more storms would form, with seven more hurricanes and three more major hurricanes. At the start of September, CSU updated their forecasts and predicted that eight more storms would form, with six more hurricanes and three major hurricanes. By the end of September, 17 named storms had developed, of which nine had developed into hurricanes and four had become major hurricanes. Within their final update for the year, CSU predicted that October would feature three named storms, two hurricanes and one major hurricane.

## Seasonal summary

With 28 storms (27 named storms and one unnamed), the 2005 Atlantic hurricane season set a new single-year record for most storms, surpassing the total of 20 from 1933. This record stood until surpassed by the 2020 season, which had 30 storms. A total of 7 named storms formed before August 1, which exceeded the record of 5 set in 1997; this record stood until 2020. The fourth named storm developed at a then-record early date, surpassed in 2012. The fifth though eleventh and the thirteenth and onward named storms developed at then-record early dates that were later surpassed in 2020. Further, the months of July and November set records for number of named storms, with 5 and 3, respectively. The 2005 season featured 15 hurricanes, surpassing the previous record of 12, set in 1969. Of the 15 hurricanes, 5 formed in September, with the season becoming only the sixth to feature 5 in that month. The 2005 season also featured a record seven major hurricanes, one more than the previous record, set in 1926, 1933, 1950, 1996, and 2004. The four Category 5 hurricanes were also a record. The season's activity was reflected with an ACE rating of 250, the second-highest value on record in the Atlantic basin, after the 1933 season.

The extremely active 2005 hurricane season was a continuation of an extended sequence of active years for tropical activity in the Atlantic. Tropical cyclone activity in the Atlantic Ocean between 1995 and 2004 was more active than any other decade in reliable record. With the exception of two years in which El Niño conditions were prevalent (1997 and 2002), all hurricane seasons were individually above average. This was associated with an active phase of the Atlantic multidecadal oscillation (AMO), with a similar period of elevated tropical activity occurring between 1950 and 1969. The anomalously frequent formation of tropical storms and hurricanes reflected the emergence of unusually warm sea surface temperatures across the tropical Atlantic. The Climate Prediction Center (CPC) predicted in May 2005 that the conditions associated with this active multi-decadal signal would continue into the 2005 hurricane season, providing favorable conditions for tropical cyclogenesis in the tropical Atlantic.

### Record activity

Chylek and Lesins (2008) determined that the likelihood of a season generating as much tropical activity as 2005 was less than 1 percent. The consecutive occurrence of hurricane seasons as active as 2004 and 2005 in the Atlantic was unprecedented. While environmental conditions favorable for the development of tropical cyclones were analogous to other active seasons, they were more pronounced and encompassed larger areas in 2005. The CPC determined that this environmental enhancement was primarily driven by four factors: the Atlantic multidecadal oscillation, the reduction of atmospheric convection in the tropical Pacific, record-high sea surface temperatures in the tropical Atlantic and Caribbean, and conducive wind and pressure patterns across the western Caribbean and Gulf of Mexico. The multidecadal oscillation increased the potency of conducive environmental factors for tropical development, including the increased strength of subtropical ridges in the northern and southern Atlantic and the eastern Pacific. This amplified the African easterly jet and enhanced upper-level easterlies, attenuating wind shear detrimental to tropical cyclogenesis across the central tropical Atlantic and the Caribbean. Frequent lulls in convection over the tropical Pacific also contributed to the strength of these ridges, focusing hurricane activity in the Atlantic. Most of the tropical storms and all major hurricanes in the Atlantic in 2005 formed when a lack of convection was present near the International Dateline, while a brief uptick in storms near the International Dateline led to a lull in tropical cyclogenesis in the Atlantic for the first half of August.

The Gulf of Mexico saw record levels of tropical activity in 2005, with 11 named storms entering the basin. The unusual activity was attributed to a persistent high pressure area over the Southeastern United States, the northeastward displacement and amplification of the Intertropical Convergence Zone (ITCZ) over the eastern Pacific, and above average sea surface temperatures in the Gulf of Mexico. These factors reduced vertical wind shear and favored cyclonic flow, creating an environment highly supportive of tropical development. The high pressure area also steered incoming storms into the Gulf of Mexico. In addition, the El Niño–Southern Oscillation (ENSO) was in a neutral phase, lowering the likelihood of storms making landfall on the East Coast of the United States and leading to a concentration of impacts farther west. This focusing mechanism led to a complementary reduction in storms developing close to Cape Verde. During the peak of the 2005 season, the Loop Current – an ocean current that transports warm water from the Caribbean Sea northward into the Gulf of Mexico and offshore the U.S. East Coast – propagated northward, reaching its most poleward point in advance of Hurricane Katrina. This protrusion detached into a warm core ring, or a small region of warm waters to an abnormally deep depth, and began to drift southwest as Hurricane Rita traversed the region. By mid-October, the Loop Current returned to its typical position in the Yucatán Peninsula. This evolution provided enhanced ocean heat content to both hurricanes and was partially responsible for the extreme intensities attained by those cyclones.

In addition to the unusually high amount of tropical activity, the 2005 season also featured an abnormally high amount of storms in the typically inactive early and latter parts of the season. Lowered sea-level atmospheric pressures in the late spring and early summer of 2005 curtailed the strength of trade winds, resulting in a reduction of latent heat loss from the tropical Atlantic and Caribbean. This allowed the persistence of the anomalously warm sea surface temperatures that had contributed to the active 2004 hurricane season; this warmth remained until November 2005. The activity in later parts of the 2005 season was elevated by the unusual development of four tropical cyclones from non-tropical origins over the eastern Atlantic.

In the wake of the season, questions arose regarding the potential impact of global warming on Atlantic hurricane activity. Hurricane experts noted that establishing a conclusive relationship would be difficult given the significant role that natural variability plays on hurricane formation and significantly improved tropical cyclone detection methods compared to decades past. A series of international workshops were established after 2005. After five years of analysis, researchers were unable to confirm whether the recent increase in tropical cyclone activity could be attributed more to climate change than natural variability. Models developed within the workshops projected that the number of tropical cyclones under Category 3 intensity would fall over the 21st century, while the number of intense Category 4–5 hurricanes would increase significantly. One potential hypothesis for these findings was a projected increase in vertical wind shear contradicted by warmer ocean temperatures for hurricanes to utilize. The team also concluded that the amount of precipitation produced by tropical cyclones would increase over the next century. In May 2020, researchers at the National Oceanic and Atmospheric Administration and the University of Wisconsin at Madison built upon this research and, for the first time, established a statistically significant global trend toward more intense tropical cyclones, particularly in the Atlantic basin. The research not only reaffirmed a trend toward stronger, wetter tropical cyclones, but it also identified a trend toward increased rapid intensification events and a general slowing of tropical cyclones' forward motion near land.

### Impacts

The storms of the season were extraordinarily damaging and were responsible for significant loss of life. Total damage is estimated to be about US\$171.7 billion, and the seasons' storms contributed to the deaths of 3,912 people. There were a record 15 storms making landfall, including seven storms that struck the United States.

The hardest-hit area was the United States Gulf Coast from eastern Texas to Florida, affected to varying degrees by Arlene, Cindy, Dennis, Katrina, Ophelia, Rita, Tammy, and Wilma. Dennis left \$2.23 billion in damage along the Florida Panhandle. Katrina caused catastrophic damage to the Gulf Coast, devastating a long stretch of coast along Louisiana, Mississippi, and Alabama with a 30-foot (9.1 m) storm surge. Wind damage was reported well inland, slowing down recovery efforts. Storm surge also breached levees in the city of New Orleans, Louisiana, flooding about 80% of the city. Total damage has been estimated at \$125 billion, making Katrina the costliest hurricane in U.S. history, surpassing Andrew in 1992 and tying Harvey in 2017. At least 1,392 people were killed by the storm, making it the deadliest hurricane in the U.S. since 1928. Southeastern North Carolina suffered some damage from the slow-moving Ophelia. Rita struck near the border of Louisiana and Texas. The hurricane re-flooded New Orleans (though to a far less degree than Katrina), and caused about \$18.5 billion in damage. Wilma caused about \$19 billion in damage when it moved across southern Florida in October. The hurricane contributed to 30 deaths, five of whom were killed directly by the storm.

Three hurricanes struck Mexico – Emily, Stan, and Wilma. Emily struck Quintana Roo and Tamaulipas as a major hurricane, causing US\$343 million (\$3.4 billion MXN) in damage. Stan killed 80 people in Mexico, and damage in the county was estimated at US\$1.2 billion (\$13.2 billion MXN). Stan was part of a broader weather system across Central America that killed 1,513 people in Guatemala, where damage was estimated at US\$996 million. Wilma dropped historic rainfall while drifting across the Yucatán peninsula. It killed four people in the country and left US\$454 million (\$4.8 billion MXN) in damage.

In the Caribbean, Cuba suffered the effects of Dennis and Wilma. The former killed 16 people and left US\$1.4 billion in damage when it struck Cuba twice. Later, Wilma flooded parts of western Cuba, leaving US\$704 million in damage. The island of Hispaniola experienced Dennis in July, which killed 56 people in Haiti. Emily killed one person and left US\$111 million in damage when it struck Grenada, and later it killed five people on Jamaica. Collectively, Dennis and Emily caused about US\$96 million (J\$6 billion) in damage to Jamaica. Wilma killed 12 people in Haiti and one in Jamaica. Alpha killed 26 people in the Caribbean. In Central America, Beta killed nine people and caused US\$11.5 million in damage when it struck Nicaragua in October. In November, Tropical Storm Gamma killed two people in Bequia in the Grenadines, 34 people in Honduras, and 3 in Belize.

Unusual impacts were felt in Europe and nearby islands. The remnants of Maria caused a landslide in Norway that killed three people. The unnamed subtropical storm in October moved through the Azores. Also in October, Vince became the first recorded tropical cyclone to strike Spain, making landfall at tropical depression intensity. In November, the extratropical remnants of Delta struck the Canary Islands, causing 7 fatalities, with 12 people missing.

## Systems

### Tropical Storm Arlene

The season's first tropical depression developed north of Honduras on June 8 from the interaction of the ITCZ and a series of tropical waves. A day later it intensified into Tropical Storm Arlene while taking a northward track. On June 10, Arlene struck western Cuba. The storm intensified further in the eastern Gulf of Mexico, reaching winds of 70 mph (110 km/h) early on June 11. Later that day, the storm moved ashore just west of Pensacola, Florida. Over the next two days, Arlene continued northward through the United States, dissipating over southeastern Canada on June 14.

In western Cuba, Arlene produced wind gusts of 49 mph (79 km/h) at Punta del Este and 6.81 in (173 mm) of rainfall in the city of Pinar del Río. Arlene left mostly minor damage throughout the United States, estimated at \$11.8 million. Storm surge damaged coastal roads in the Florida Panhandle and Alabama. In Miami Beach, Florida, a student died when she was caught in a rip current. Rainfall in the United States peaked at 9.84 in (250 mm) in Lake Toxaway, North Carolina. The remnants of Arlene dropped approximately 6 to 7 in (150 to 180 mm) of rainfall in Warren County, New York, in just two hours, washing out several roadways and flooding numerous homes.

### Tropical Storm Bret

Between June 24 and June 27, a tropical wave and weak low-pressure area moved in tandem across Central America and eastern Mexico. The system then reached the Bay of Campeche early on June 28 and quickly organized into a tropical depression that day around 18:00 UTC. Six hours later, at 00:00 UTC on June 29, the depression intensified into Tropical Storm Bret and peaked with sustained winds of 40 mph (64 km/h). Bret moved ashore northeastern Mexico near Tuxpan, Veracruz, around 12:00 UTC, dissipating early on June 30 over San Luis Potosí.

Bret brought heavy rainfall across Mexico, reaching at least 10.47 in (266 mm) in El Raudal, Veracruz. One person drowned in Cerro Azul, while another death occurred in Naranjos due to cardiac arrest. The floods forced the evacuation of approximately 2,800 people, damaged around 3,000 houses, isolated 66 villages, and caused about \$100 million (MXN, US\$9.2 million) in damage.

### Hurricane Cindy

A tropical depression formed on July 3 in the western Caribbean Sea from a tropical wave that moved off Africa nine days prior. The depression crossed the Yucatán Peninsula and dropped rainfall, reaching 2.8 in (71 mm) in Cancún. The system entered the Gulf of Mexico, strengthening into Tropical Storm Cindy early on July 5. Cindy intensified further into a minimal hurricane early on July 6, with peak winds of 75 mph (121 km/h). The hurricane struck southeastern Louisiana and later southern Mississippi. Cindy continued across the southeastern United States and transitioned into an extratropical cyclone on July 7 over The Carolinas; it eventually dissipated over the Gulf of St. Lawrence on July 12.

Across the United States, the hurricane caused \$320 million in damage and three fatalities – one in Georgia from flooding, and two in Maryland from a car crash. Across Louisiana, the hurricane left 280,000 people without power. Rainfall in the United States peaked at 9.50 in (241 mm) in Saint Bernard, Louisiana. Cindy spawned a large tornado outbreak, including an F2 tornado near Hampton, Georgia, that caused over \$40 million in damage at the Atlanta Motor Speedway alone. The same tornado inflicted severe damage to 11 planes and 5 vintage helicopters at Tara Field and impacted hundreds of homes to some degree.

### Hurricane Dennis

A tropical wave led to the development of Tropical Depression Four in the southeastern Caribbean late on July 4 and further strengthened into Tropical Storm Dennis early the next day. The storm moved west-northwestward, strengthening into a hurricane on July 6 to the south of Hispaniola. On the next day, Dennis rapidly intensified into a Category 4 hurricane while moving between Jamaica and Haiti. Early on July 8, the hurricane briefly moved over Granma Province in southeastern Cuba. After briefly weakening, Dennis restrengthened to attain peak winds of 150 mph (240 km/h) in the Gulf of Guacanayabo, making it the strongest Atlantic hurricane before August; its record was broken eight days later by Hurricane Emily. Later on July 8, Dennis moved ashore again in Matanzas Province. The hurricane crossed Cuba entered the Gulf of Mexico on July 9 as a weakened hurricane. Dennis re-intensified to a secondary peak of 145 mph (233 km/h) on July 10, only to weaken prior to its final landfall later that day near Pensacola, Florida. Dennis weakened and moved through the southeastern United States, the Ohio Valley, and eventually dissipating on July 18 over Ontario.

The outer rainbands of Dennis produced widespread flooding and landslides in Haiti, killing at least 56 people and leaving US\$50 million in damage. Dennis brought torrential rain to Jamaica, reaching 24.54 in (623 mm) in Mavis Bank. One person died in Jamaica, and damage was estimated at US\$31.7 million. The storm's heaviest rainfall occurred in Cuba, reaching 43.0 in (1,092 mm), making Dennis the wettest storm for the island since Hurricane Flora of 1963. Across the island, Dennis killed 16 people, and left US\$1.4 billion in damage, affecting agriculture, tourist areas, infrastructure, and houses. Dennis moved ashore Florida near where Hurricane Ivan struck ten months prior. Damage from Dennis in the United States totaled \$2.545 billion, and there were 15 deaths in the country, all but one in Florida. Rainfall in the United States reached 12.80 in (325 mm) near Camden, Alabama.

### Hurricane Emily

On July 11, a tropical wave spawned a tropical depression east of the Lesser Antilles which quickly intensified into Tropical Storm Emily. Moving westward, Emily strengthened into a minimal hurricane and struck Grenada at that intensity on July 14. Continuing across the Caribbean Sea, Emily eventually strengthened into a Category 5 hurricane on July 16 to the southwest of Jamaica, reaching peak winds of 160 mph (260 km/h). Emily broke the record set by Dennis for the strongest Atlantic hurricane before August. Emily weakened after its peak intensity, striking the northeastern Yucatán Peninsula on July 18 with winds of 135 mph (217 km/h). Emily emerged into the Gulf of Mexico and restrengthened, making another landfall in Mexico on July 18 in Tamaulipas with winds of 125 mph (201 km/h). A day later, Emily dissipated over land. Emily was the earliest 5th named storm before being surpassed by Tropical Storm Edouard in 2020.

In Grenada, Emily killed one person and caused US\$111 million in damage, with thousands of roofs damaged. The hurricane's large circulation also damaged houses in other nearby islands. Heavy rainfall from Emily affected Haiti, killing five people. In Jamaica, Emily produced 15.43 in (392 mm) of rainfall; associated flooding killed five people on the island. Collectively, Emily and earlier Hurricane Dennis left about US\$96 million (J\$6 billion) in damage to Jamaica. In Honduras, a man drowned in a river swollen by rains from Emily. Damage was heaviest where Emily made its two landfalls in Mexico, with damage in the country estimated at US\$343 million (\$3.4 billion MXN). Two helicopter pilots were killed when their aircraft crashed while evacuating offshore oil platforms operated by Pemex. A man in Playa del Carmen was electrocuted to death while preparing for the hurricane. The outskirts of Emily dropped heavy rainfall in southern Texas, damaging about \$4.7 million worth of cotton.

### Tropical Storm Franklin

Tropical Depression Six formed northeast of the Bahamas on July 21, originating from a tropical wave that exited the coast of Africa on July 10. The depression quickly intensified into Tropical Storm Franklin, but wind shear disrupted the storm's initial development. As the storm moved to the north and northeast, it intensified; on July 23, Franklin attained peak winds of 70 mph (110 km/h). Three days later the storm passed west of Bermuda. An approaching trough turned Franklin to the northwest and weakened Franklin to a minimal tropical storm. Franklin restrengthened slightly as it accelerated northeastward. On July 30, the storm transitioned into an extratropical cyclone south of Nova Scotia, and a day later it was absorbed by a larger extratropical storm near Newfoundland. Franklin held the record for the earliest sixth named storm until it was broken by Tropical Storm Fay in 2020.

On July 26, Bermuda recorded wind gusts of 37 mph (60 km/h) while the storm made its closest approach. The storm brought light rainfall to Newfoundland.

### Tropical Storm Gert

A tropical wave, the same that spawned Tropical Storm Franklin, moved off Africa on July 10. It tracked west-northwest into the Bay of Campeche on July 23, where it contributed to the development of a tropical depression later that day. As convection increased near the center, the depression intensified into Tropical Storm Gert early on July 24. The cyclone did not persist long over water, instead moving ashore north of Cabo Rojo, Mexico, with 45 mph (72 km/h) winds early on July 25. It continued inland, affecting the same areas impacted by Hurricane Emily just days prior, and quickly dissipated over high terrain at the end of that day.

Gert dropped heavy rainfall, reaching 8.46 in (214.9 mm) in San Luis Potosí. Gert caused about US\$6 million (\$60 million 2005 MXN) in damage, and resulted in one fatality in Nuevo León. Gert was the earliest seventh named storm until it was surpassed by Tropical Storm Gonzalo in 2020.

### Tropical Storm Harvey

Tropical Depression Eight formed on August 2 southwest of Bermuda from a tropical wave that left the African coast on July 22. The depression strengthened into Tropical Storm Harvey on August 3 while moving northeastward. Due to strong wind shear, Harvey initially exhibited subtropical characteristics. On August 4, Harvey passed 45 miles (72 km) south of Bermuda. After moving away from the island, Harvey attained peak winds of 65 mph (105 km/h) late on August 4 and continued northeastward for a few days, transitioning into an extratropical storm on August 9. The storm gradually weakened and eventually dissipated northwest of the Azores on August 14. Harvey was the earliest eighth named storm on record before being surpassed by Hurricane Hanna during the 2020 Atlantic hurricane season.

On Bermuda, Harvey dropped 5.02 in (128 mm) of rainfall at Bermuda International Airport, flooding some roads. Sustained winds on the island reached 45 mph (72 km/h).

### Hurricane Irene

A high-latitude tropical wave led to the genesis of Tropical Depression Nine west of Cabo Verde on August 4. It moved to the northwest without much initial development. On August 7, the depression strengthened into Tropical Storm Irene, only to weaken into a tropical depression again the next day. Irene turned to the west, and later resumed its northwest track. It re-intensified into a tropical storm on August 11. On August 15, the storm turned to the north, passing between Bermuda and North Carolina. On the next day, it strengthened into a hurricane. Irene intensified further after turning to the northeast and later east. Late on August 16, the cyclone attained peak winds of 105 mph (169 km/h). An approaching trough weakened Irene and caused it to accelerate northeastward. On August 18, Irene weakened into a tropical storm, and later that day was absorbed by a larger extratropical storm to the southeast of Newfoundland. Rip currents near Long Beach, New York killed a 16-year-old boy. Irene was the earliest ninth named storm on record before being surpassed by Hurricane Isaias in 2020.

### Tropical Depression Ten

Tropical Depression Ten formed between the Lesser Antilles and Cape Verde on August 13 from a tropical wave that entered the Atlantic five days earlier. The depression moved slowly westward in an environment of strong vertical shear. Some weather models predicted relaxing shear and intensification of the system; however, the hostile conditions ripped the system apart, causing the depression to degenerate into a remnant low, and the NHC discontinued advisories on August 14, when no organized deep convection remained. The remnants of Tropical Depression Ten continued drifting northwestward, before degenerating further into a tropical wave north of the Leeward Islands, on August 18. Soon afterward, the low-level and mid-level circulations split, with the mid-level circulation lagging behind to the east. The remnant low-level circulation continued westward, before dissipating near Cuba on August 21. Producing occasional bursts of convection, the mid-level remnant circulation eventually merged with another tropical wave approaching from the east, on August 19. This new system would become Tropical Depression Twelve over the Bahamas and, eventually, Hurricane Katrina.

### Tropical Storm Jose

A tropical wave, plausibly the same that spawned Tropical Depression Ten nine days earlier, led to the formation of Tropical Depression Eleven over the Bay of Campeche on August 22. The depression strengthened into Tropical Storm Jose later that day and achieved a maximum strength of 60 mph (97 km/h). Jose made landfall in the Mexican state of Veracruz near the Laguna Verde Nuclear Power Station on August 23. The cyclone became more organized two hours before making landfall and was forming an eye, but its winds remained under hurricane strength. Jose rapidly weakened and soon dissipated as it moved inland over Mexico. Jose was the earliest 10th named storm until surpassed by Tropical Storm Josephine in 2020.

While drenching Mexico's Gulf coast, Jose forced some 25,000 residents from their homes in Veracruz state and damaged at least 16,000 homes in the state. Jose killed 11 people in Veracruz and 5 in Oaxaca. Damage in Mexico totaled roughly \$45 million.

### Hurricane Katrina

A tropical depression developed on August 23 from the complex interaction of a tropical wave, the mid-level remnants of Tropical Depression Ten, and a nearby upper-level trough. The depression became a tropical storm on August 24 and a hurricane on August 25, making landfall as a Category 1 hurricane in southeastern Florida. Katrina imparted about \$500 million in crop and infrastructure damage to the state. The hurricane quickly crossed Florida and emerged into the Gulf of Mexico. Katrina rapidly intensified to Category 5 status early on August 28, becoming the seventh most intense Atlantic hurricane. Turning northward, the hurricane weakened as it approached the northern Gulf Coast. On August 29 at 11:10 UTC, Katrina made landfall in southeastern Louisiana as a Category 3 hurricane, with 125 mph (201 km/h) winds, and a barometric pressure of 920 mbar (27 inHg); it was the third lowest pressure for a landfalling United States hurricane at the time, and fourth as of 2018. Katrina then crossed the Breton Sound, making a third and final landfall with 120 mph (190 km/h) winds near Pearlington, Mississippi. The cyclone quickly weakened after moving inland and became extratropical over Kentucky on August 30.

On August 28, the New Orleans National Weather Service issued an urgent weather bulletin describing potentially catastrophic impacts, comparing Katrina to Hurricane Camille of 1969. That same day, New Orleans mayor Ray Nagin issued the city's first-ever mandatory evacuation. About 80% of the city and 83% of neighboring Jefferson Parish evacuated ahead of the storm. The hurricane left catastrophic damage across southern Louisiana, with more than 300,000 houses damaged or destroyed; most of these were in Orleans Parish. In New Orleans, storm surge breached the levees along the Gulf Intracoastal Waterway and 17th Street and London Avenue Canals, flooding about 80% of the city. Portions of the city remained underwater for 43 days. The Mississippi and Alabama coastlines also suffered catastrophic damage from the storm's 30 ft (9.1 m) storm surge, with very few structures remaining on the coast of the former. Across the region, the hurricane flooded and ruined about 350,000 vehicles. About 2.4 million people lost access to clean drinking water. Katrina also spawned an outbreak of 62 tornadoes across the eight states in the eastern United States.

Hurricane Katrina imparted catastrophic damage in portions of Louisiana and Mississippi, with overall damage estimated at \$173 billion; this makes Katrina the costliest natural disaster in U.S. history. Throughout the United States, Katrina killed 1,392 people, making it one of the deadliest hurricanes in the United States, and the deadliest American hurricane since 1928. The Federal Emergency Management Agency (FEMA) managed the aftermath of the hurricane, and faced criticism for its response time, lack of coordination with state agencies, supply shortages, and insufficient housing for federal workers. Tens of thousands of people lost their jobs following the hurricane. Residents across the New Orleans area suffered health effects, including rashes and respiratory problems, from polluted water and air following the hurricane. Katrina forced about 800,000 people to move temporarily, which was the greatest number of displaced people in the country since the Dust Bowl. The United States federal government spent \$110.6 billion in relief, recovery and rebuilding efforts, including \$16 billion toward rebuilding houses, which was the nation's largest ever housing recovery project. Within a year of the storm, most of the levees were largely repaired. Various countries and international agencies sent supplies or financial aid to assist in the hurricane response.

### Tropical Storm Lee

A tropical wave moved off the coast of Africa on August 24. It developed into Tropical Depression Thirteen on August 28 while 960 miles (1,540 km) east of the Lesser Antilles. Strong wind shear prevented much organization, and the depression degenerated into a low pressure area late on August 29. The remnants moved to the north and northeast, steered by a larger non-tropical system to the north. The convection increased on August 31; that day the system regenerated into a tropical depression, which strengthened further into Tropical Storm Lee. The storm attained peak winds of 40 mph (64 km/h) while located between Bermuda and the Azores. After 12 hours as a tropical storm, Lee weakened back to a tropical depression as it turned to the northwest, steered by the larger non-tropical storm. On September 2, the depression degenerated into a remnant low, which was absorbed by a cold front two days later.

### Hurricane Maria

A strong tropical wave entered the eastern Atlantic on August 27. The broad disturbance was initially hindered by strong wind shear but eventually organized into a tropical depression about halfway between the Leeward Islands and Cabo Verde early on September 1. The tropical cyclone moved northwest and steadily organized as upper-level winds became more conducive. It strengthened into Tropical Storm Maria on September 2 and eventually became the sixth hurricane of the season early on September 4. As the cyclone developed a well-defined eye, Maria reached peak winds of 115 mph (185 km/h), Category 3 strength, early on September 6. Around the time of its peak, Maria turned to the north and northeast, moving around the subtropical ridge as it gradually weakened. Maria fell to tropical storm intensity on September 9 and became extratropical a day later between Newfoundland and the Azores. The former hurricane re-intensified over the northern Atlantic Ocean, only to weaken before passing near southern Iceland. On September 14, the extratropical storm that was once Maria merged with another extratropical storm while approaching Norway.

The remnants of Maria brought resulted in heavy rainfall to Norway, triggering a landslide in Bergen that killed three people and injured seven others.

### Hurricane Nate

A tropical wave left Africa on August 30 and moved into the southwestern Atlantic, where subsequent interaction with an upper-level low led to the genesis of a tropical depression south-southwest of Bermuda on September 5. This depression quickly intensified into Tropical Storm Nate, which moved slowly northeastward. On September 7, Nate intensified into the seventh hurricane of the season. A day later, the hurricane passed southeast of Bermuda, where it produced wind gusts of 50 mph (80 km/h). Early on September 9, Nate attained peak winds of 90 mph (140 km/h) as it accelerated northeastward ahead of a trough. The same trough created unfavorable conditions, causing Nate to weaken quickly back to tropical storm status. On September 10, Nate transitioned into an extratropical storm which was absorbed by a larger extratropical storm near the Azores on September 13.

Canadian Navy ships headed to the U.S. Gulf Coast to help in the aftermath of Hurricane Katrina were slowed down trying to avoid Nate and Ophelia. Rip currents caused by hurricanes Nate and Maria killed one person in New Jersey and severely injured another person.

### Hurricane Ophelia

The interplay of a cold front and a trough led to the development of Tropical Depression Sixteen over the northern Bahamas on September 6. The depression strengthened into Tropical Storm Ophelia on September 7 and briefly into a hurricane on September 9 while stalled off the east coast of Florida. Ophelia fluctuated between hurricane and tropical storm intensity for the next week as it meandered off the southeastern United States. Twice it attained peak winds of 85 mph (137 km/h). On September 14, the northern eyewall moved over the North Carolina coast from Wilmington to Morehead City. After moving away from the state, Ophelia weakened to tropical storm status for a fourth and final time due to stronger wind shear and dry air. The storm accelerated northeastward and passed southeast of Cape Cod. Ophelia transitioned into an extratropical storm on September 18 and subsequently crossed Nova Scotia and Newfoundland, eventually dissipating on September 23 north of the Scandinavian Peninsula.

Ophelia caused significant coastal erosion from the churning waves. The hurricane caused extensive damage in the Outer Banks and around Cape Fear. Damage in the United States was estimated at \$70 million. The storm's remnants produced strong winds and heavy rain over Atlantic Canada. Ophelia killed three people – a drowning in Florida from high surf, a traffic fatality in North Carolina, and a death from a fall in Nova Scotia.

### Hurricane Philippe

On September 17, Tropical Depression Seventeen formed from a tropical wave about 350 miles (560 km) east of Barbados. It quickly intensified into Tropical Storm Philippe while taking a track to the north-northwest. Early on September 19, Philippe attained hurricane status and reached peak winds of 80 mph (130 km/h) a day later. Wind shear from an upper-level low caused the hurricane to weaken back to a tropical storm, exposing the center from the convection. On September 21, Philippe accelerated to the north and began moving around the upper-level low, which had extended to the surface and developed into a non-tropical cyclone. The storm briefly threatened Bermuda as it turned to the northwest and began a counterclockwise loop. On September 23, Philippe weakened to a tropical depression and later a remnant low; it was absorbed by the larger non-tropical cyclone a day later.

Philippe brought gusty winds and moisture to Bermuda, with 0.15 inches (3.8 mm) of precipitation reported on September 23. The circulation that absorbed Philippe dropped light rainfall on the island, and was responsible for the lowest barometric pressure during the month. When Philippe formed in September 17, Philippe became the earliest 16th named storm on record until the record was broken by 2020's Hurricane Paulette by 10 days.

### Hurricane Rita

In mid-September, the southern extent of a stationary front devolved into a trough north of the Leeward Islands. A tropical wave interacted with this feature to form a tropical depression near the Turks and Caicos Islands on September 18. It organized into Tropical Storm Rita later that day. Moving to the west-northwest, the storm's intensification attenuated over the Bahamas before resuming thereafter, becoming a hurricane on September 20 between Cuba and Florida. Rapid intensification ensued as Rita moved into the Gulf of Mexico. Late on September 21, Rita strengthened into a Category 5 hurricane, and the next day it attained peak winds of 180 mph (290 km/h). Its minimum pressure of 895 mbar (895 hPa; 26.4 inHg) was the lowest of any storm in the Gulf of Mexico on record. The hurricane weakened as it approached the northwest Gulf Coast. On September 24, Rita made landfall near the Texas–Louisiana border with sustained winds of 115 mph (185 km/h). It rapidly weakened over land as it turned to the north and northeast, and was later absorbed by an approaching cold front on September 26 over Illinois.

Across the United States, Rita imparted \$18.5 billion in damage and killed 120 people, although only seven deaths were directly related to the hurricane. Early in its evolution, Rita flooded houses in northern Cuba and the Florida Keys. Rita's approach to the U.S. Gulf Coast prompted one of the largest mass evacuations in the country's history, with an estimated 3.7 million people fleeing the Texas coast between Corpus Christi and Beaumont. Due in part to high temperatures preceding Rita's landfall and elderly susceptibility to excessive heat, at least 80 people died during the mass evacuation; a coach fire en route to Dallas claimed 23 lives. Rita generated a 15-foot (4.6 m) storm surge that devastated parts of Cameron Parish in Louisiana, destroying most structures in towns like Cameron and Holly Beach. Storm surge also damaged homes in adjoining Jefferson County in Texas. In New Orleans, Rita produced additional flooding and overtopped levees that had been repaired after Hurricane Katrina a month earlier. Impacts from heavy rainfall, gusty winds, and tornadoes associated with Rita affected much of the lower Mississippi River Valley, and over a million electricity customers lost power.

A third of Cameron Parish's population left the parish following the devastation wrought by Rita. FEMA granted over \$1.3 billion to Louisiana to support recovery efforts; \$668.8 million was allocated in the form of public assistance grants for initial recovery measures, and \$523.5 million was sent to individuals as part of the agency's Individuals and Households program. Over \$1 billion in federal assistance was also disbursed to Texas. Texas' Community Development Block Grant Disaster Recovery Program aided 1.85 million people in addition to supporting longer-term infrastructure repairs.

### Tropical Depression Nineteen

On September 30, a tropical wave developed into Tropical Depression Nineteen to the west of Cabo Verde. The newly formed cyclone exhibited deep convection in the southern semicircle, but its cloud pattern quickly deteriorated under the influence of strong wind shear. The system moved northwestward and failed to intensify beyond winds of 35 mph (56 km/h), instead dissipating on October 2 without affecting land.

### Hurricane Stan

A tropical wave emerged from Africa on September 17 and moved across the central Atlantic, hampered by north-northeasterly wind shear. The disturbance eventually traveled into the western Caribbean Sea, where it organized into a tropical depression southeast of Cozumel around 12:00 UTC on October 1. High pressure directed the cyclone toward the west-northwest, and the depression intensified into Tropical Storm Stan shortly before making landfall along the eastern coast of the Yucatan Peninsula. Stan briefly weakened to a tropical depression as it crossed over land, but it regained tropical storm strength over the Bay of Campeche on October 3, when ridging further intensified and forced the storm west-southwest. Rapid intensification ensued, allowing Stan to become a Category 1 hurricane before its second landfall east-southeast of Veracruz early on October 4. Once inland, the system rapidly unraveled over the mountainous terrain of Mexico, dissipating in the state of Oaxaca just after 06:00 UTC on October 5.

Stan killed 80 people in Mexico, and damage in the county was estimated at US\$1.2 billion (\$13.2 billion MXN). Stan was associated with a larger weather system across eastern Mexico and Central America. Torrential rainfall across this region killed 1,513 people in Guatemala, making it the deadliest natural disaster in the country's history. Damage in Guatemala was estimated at US\$996 million. El Salvador's Santa Ana Volcano erupted on October 1, occurring simultaneous to the flooding. The flooding killed 69 people in the country, and damage from the two disasters was estimated at US\$355.6 million. In Honduras, the weather system killed seven people and left US\$100 million in damage. There were also three deaths in Nicaragua and one in Costa Rica. Road damage in Costa Rica from Stan and earlier Hurricane Rita was estimated at US\$57 million (₡28 billion (CRC).

### Unnamed subtropical storm

In the post-season analysis, the National Hurricane Center identified an additional subtropical storm that had gone unclassified during the course of the season. In late September, an upper-level low formed west of the Canary Islands and moved westward, organizing into a subtropical depression early on October 4. It quickly intensified into a subtropical storm while curving northeast ahead of an approaching cold front. The storm attained peak winds of 50 mph (80 km/h) as it moved through the eastern Azores, where Santa Maria Island reported sustained winds up to 40 mph (64 km/h). Early on October 5, the storm merged with the cold front; later that day, its remains were absorbed by a non-tropical low. The low that absorbed the storm would eventually become Hurricane Vince.

### Tropical Storm Tammy

On October 5, Tropical Storm Tammy developed east of Florida following the interaction of a tropical wave and an upper-level trough. That day, it strengthened to reach peak winds of 50 mph (80 km/h) and made landfall near Jacksonville, Florida. Tammy weakened as it moved inland, crossing southern Georgia and Alabama. It was absorbed by a larger extratropical storm on October 6. Tammy dropped locally heavy rainfall along its path, causing minor damage. The frontal system that absorbed Tammy was a partial cause for severe flooding in New York, New Jersey and New England that killed 10 people in mid-October.

### Subtropical Depression Twenty-Two

Subtropical Depression Twenty-Two formed from a non-tropical low 450 miles (720 km) southeast of Bermuda on October 8. The system encountered unfavorable conditions as it turned westward and degenerated into a remnant low on October 10, before becoming extratropical on the following day. The NHC continued to monitor the remnant as it headed towards the East Coast of the United States. The extratropical system transported tropical moisture northward, and was, along with Tropical Storm Tammy, a partial cause of severe flooding in New York, New Jersey and New England during early-to-mid-October. The flooding killed 10 people after 6 to 10 in (150 to 250 mm) of precipitation fell in some locales.

### Hurricane Vince

Subtropical Storm Vince formed in the eastern Atlantic near Madeira on October 8 from the same non-tropical low that absorbed the unnamed subtropical storm. Vince transitioned into a tropical storm on the following day and was upgraded to a hurricane shortly thereafter. Although Vince was a very small and short-lived storm that only briefly reached hurricane strength, it was notable for developing in the northeastern Atlantic, well away from where hurricanes usually form. Vince made landfall on the Iberian Peninsula near Huelva, Spain, on October 11 just after weakening to a tropical depression. Vince was the first tropical cyclone on record to make landfall in Spain. The storm left minor flooding in some areas.

### Hurricane Wilma

An upper-level low over the southwestern Atlantic helped facilitate the formation of a large, monsoon-like gyre over the Caribbean Sea in middle October. A series of tropical waves moved into this area of disturbed weather and helped form a low-pressure system that developed into Tropical Depression Twenty-Four southwest of Jamaica on October 15. It intensified into Tropical Storm Wilma two days later. Wilma moved slowly through the warm waters of the western Caribbean Sea and began a period of rapid deepening on October 18 that lasted into the following day. This culminated in the cyclone attaining Category 5 hurricane status, reaching peak winds of 185 mph (298 km/h) and setting a record for the lowest barometric pressure in an Atlantic hurricane; at 12:00 UTC on October 19, hurricane hunters recorded a pressure of 882 mbar (26.0 inHg) in the center of the tiny, well-defined eye of Wilma. Wilma weakened to Category 4 intensity by the time it made landfall on Cozumel on October 21. It later crossed the northeastern Yucatán Peninsula and emerged into the Gulf of Mexico, turning northeast. On October 24, Wilma made landfall in southwestern Florida at Cape Romano with winds of 120 mph (190 km/h). The hurricane quickly crossed the state and continued across the western Atlantic Ocean. Wilma transitioned into an extratropical cyclone on October 26, which was absorbed by a larger extratropical storm a day later over Atlantic Canada.

In its formative stages, Wilma's large circulation spread across much of the western Caribbean Sea, killing 12 people in Haiti and one in Jamaica. Wilma set a record in Mexico, and for the entire Western Hemisphere, for the highest 24 hour rainfall total, with 64.330 in (1,633.98 mm) recorded at Isla Mujeres. There were four deaths in Mexico, and nationwide damage was estimated at US\$454 million (\$4.8 billion MXN). Local and federal troops quelled looting and rioting in Cancún. Cancún's airport was closed to the public in the days after the storm, forcing stranded visitors to fly out of Mérida, Yucatán, the region's closest functioning airport. On November 28, Mexico declared a disaster area for 9 of Quintana Roo's 11 municipalities. Mexico's development bank – Nacional Financiera – provided financial assistance for businesses affected by Wilma and Stan through a \$400 million fund (MXN, US\$38 million).

A significant storm surge flooded areas of western Cuba, leaving US\$704 million in damage. In Florida, Wilma caused \$19 billion in damage and killed 30 people; five of the deaths were caused directly by the hurricane. Wilma's storm surge caused the worst flooding in the Florida Keys since Hurricane Betsy in 1965. Wilma inflicted a multi-billion dollar disaster in the Miami metropolitan area, including \$2.9 billion in damage in Palm Beach County, \$2 billion in Miami-Dade County, and \$1.2 billion in Broward County. Numerous homes and businesses experienced some degree of impact, with over 55,000 dwellings and 3,600 workplaces damaged in Palm Beach County alone. On October 24, 2005, the same day Wilma made landfall in Florida, President George W. Bush approved a disaster declaration for 13 Florida counties. FEMA expended \$342.5 million to the 227,321 approved applicants. Additionally, public assistance from FEMA totaled over \$1.4 billion and grants for hazard mitigation projects exceeded \$141.5 million. After leaving Florida, Wilma killed one person and left US\$6.4 million in damage to the Bahamas, when it passed northwest of the country. On Bermuda, Hurricane Wilma produced wind gusts of 51 mph (82 km/h).

### Tropical Storm Alpha

A tropical wave organized into Tropical Depression Twenty-Five in the eastern Caribbean on October 22. Later that day, the depression strengthened into Tropical Storm Alpha as it moved west-northwestward. Around 10:00 UTC on October 23, Alpha made landfall near Barahona, Dominican Republic, with winds of 50 mph (80 km/h). Alpha weakened to a tropical depression over Hispaniola's steep mountains. The cyclone emerged into the Atlantic Ocean, where it was absorbed by Hurricane Wilma on October 24. Alpha was the 22nd named system in the 2005 Atlantic hurricane season, breaking the 1933 season's record, and became the first tropical storm to be named using the Greek Alphabet. The storm claimed 26 lives, with more than half of them in Haiti. Alpha destroyed 43 homes and damaged 191 others in Haiti.

### Hurricane Beta

Late on October 26, the same tropical wave that spawned Tropical Storm Alpha led to the formation of Tropical Depression Twenty-Six over the southwestern Caribbean Sea. Early the next day, it was upgraded to Tropical Storm Beta. The storm strengthened into a hurricane on October 29 and reached major hurricane intensity on October 30, with sustained winds around 115 mph (185 km/h). That brought the total number of major hurricanes in the 2005 season to seven, a record breaking achievement. However, Beta weakened to a Category 2 prior to landfall in Nicaragua. The storm rapidly weakened inland and dissipated on October 31.

The Colombian island of Providencia was subjected to hurricane-force winds for several hours as the center of the storm moved very slowly by the island. Reports indicate extensive damage to homes and a loss of communications with the islanders. In Honduras and Nicaragua, over 1,000 structures were damaged by the storm, hundreds of which were destroyed. Overall, Beta caused nine fatalities and more than \$15.5 million in damage across four countries.

### Tropical Storm Gamma

Late on November 13, Tropical Depression Twenty-Seven formed from a tropical wave about 115 mi (185 km) west-southwest of St. Lucia. While passing through the Lesser Antilles, the heavy rainfall caused mudslides, killing two people on Bequia. The cyclone briefly attained tropical storm status, but wind shear prevented further development of the system, and advisories were discontinued on November 16 as it lost its closed circulation about 305 mi (490 km) southeast of Kingston, Jamaica. The remnants of the depression continued westward and moved along the northern shore of Honduras, merging with parts of a larger low pressure system. It is uncertain whether the remnants of Gamma absorbed the low pressure system or vice versa. The storm strengthened and a closed circulation formed on November 18, making Gamma a tropical storm for the second time. After regeneration, and after making landfall over northern Honduras, floods from Gamma killed 34 people in Honduras. Three people died in Belize related to the storm. Gamma meandered in the Caribbean Sea for a short time, until slowly weakening and eventually disintegrating into a remnant low late on November 20. The storm caused 39 deaths in total.

### Tropical Storm Delta

Delta originated from a broad and non-tropical low-pressure area that arose 1,380 miles (2,220 km) southwest of the Azores on November 19, initially moving northeast along the trailing fringes of a passing cold front. Convection developed atop the center of the nascent disturbance two days later, and satellite data suggested that it was acquiring thermodynamic characteristics exhibited by tropical cyclones. On November 22, the NHC classified the low-pressure system as a subtropical storm with the name Delta. Delta took a south-southwestward course and further coalesced its associated showers, leading to its re-designation as a tropical storm on November 23. It stalled 1,320 miles (2,120 km) west-southwest of the Canary Islands and attained peak winds of 70 mph (110 km/h) on November 24. Delta moved erratically over the next two days and weakened to a low-end tropical storm in response to increasing wind shear. A strengthening trough over western Europe accelerated Delta towards the east-northeast on November 27, concurrent with the brief emergence of an eye and a period of intensification. Delta's tropical characteristics later succumbed to wind shear and cold air, resulting in its extratropical transition on November 28 while 250 miles (400,000 m)i) west-northwest of the western Canary Islands; as an extratropical system, Delta tracked east, passing north of the Canary Islands before moving into Morocco and Algeria on November 29, where it dissipated.

Delta caused severe damage in the Canary Islands and claimed at least seven lives, including six who drowned after boats overturned; there were 12 people missing from the overturned boat. El Dedo de Dios, a geological feature which had been pointing towards the sky for over a millennium and an important landmark for the Canary Islands, was toppled during the storm. Damage throughout the Canary Islands was estimated at €312 million (\$364 million 2005 US dollars). Delta also caused power outages, leaving some 200,000 people without power and forcing airports to close down. The remnants of Delta later moved into Morocco, bringing needed rain.

### Hurricane Epsilon

A surface low attached to a stationary front formed underneath an upper-level low east of Bermuda on November 27. The surface low detached from the frontal zone and acquired tropical characteristics as deep convection wrapped around its center, leading to the development of Tropical Storm Epsilon early on November 29. The NHC consistently forecast that the storm would weaken; however, Epsilon gradually intensified as it moved westward and later looped to the northeast. The storm attained hurricane status on December 2 as the track shifted to the east. Neither Epsilon's structure or strength changed appreciably over the next few days, and it attained peak winds of 85 mph (137 km/h) on December 5. A building ridge turned Epsilon to the southwest on December 6, and it maintained its intensity due to low wind shear. Epsilon remained a hurricane until December 7, its fifth hurricane day, the longest for a for any Atlantic tropical cyclone in December. Epsilon degenerated into a remnant low on December 8; the circulation dissipated two days later.

### Tropical Storm Zeta

Towards the end of December, an upper-level low interacted with a cold front, which produced an area of low-pressure by December 28, about 750 mi (1,205 km) to the west-northwest of Cabo Verde. Over the next couple of days, the system developed a low-level circulation and atmospheric convection increased as it moved north-westwards, before the NHC classified it as Tropical Storm Zeta during December 30. As a result, Zeta became the second latest-forming tropical cyclone in the Atlantic on record behind Alice of December 1954. Over the next couple of days, the system gradually intensified further in a region of favorable anticyclonic outflow, as it slowly moved west-northwest in response to a mid-level low to the southwest. During January 1, Zeta became only the second tropical storm on record to exist in two calendar years, while it peaked with 1-minute sustained winds of 65 mph (105 km/h). It weakened on January 2, only to re-intensify to its peak intensity on January 3. Zeta weakened again as it turned westward, degenerating into a remnant low on January 6; the circulation dissipated on the next day to the southeast of Bermuda. Zeta affected the 2005 Atlantic Rowing Race by producing high swells that moved boats off course.

## Storm names

The list below highlights the names used in the 2005 Atlantic hurricane season. This was the same list used for the 1999 season, with the exceptions of Franklin and Lee, which replaced Floyd and Lenny. The names not retired from this list were used again in the 2011 season. The names Franklin, Lee, Maria, Nate, Ophelia, Philippe, Rita, Stan, Tammy, Vince and Wilma from the regular list were used for the first (and only, in the cases of Rita, Stan and Wilma) time this year, as were the auxiliary list Greek letter names of Alpha, Beta, Gamma, Delta, Epsilon and Zeta. The 2005 season was the first Atlantic hurricane season to have storm names beginning with 'V' and 'W'. Also, when the list of 21 storm names pre-approved for the season by the World Meteorological Organization (WMO) was exhausted, 2005 became the first to move into the auxiliary list of names.

### Retirement

After the season had ended, the WMO's hurricane committee retired five names: Dennis, Katrina, Rita, Stan and Wilma and replaced them with Don, Katia, Rina, Sean and Whitney for the 2011 season. This surpassed the previous record for the number of hurricane names retired after a single season – four, held by the 1955, 1995, 2004 seasons.

There was considerable discussion on the usage of the Greek alphabet. The committee agreed that the usage of the Greek alphabet had a "major important political, economic and social impact globally, which might not have happened if a secondary or circular list of names had been used", and that the Greek alphabet would be used again if the traditional naming list was exhausted. It was also decided that it was not practical to retire a Greek letter. Storms named with Greek letters that would otherwise be eligible for retirement would appear in the retired name list, but have a notation affixed with the circumstances. However, due to the devastation caused by Eta and Iota during the 2020 season, the next season that the auxiliary Greek alphabet had to be used, the WMO decided to discontinue the entire Greek alphabet to avoid any confusion and replaced it with a new auxiliary list of given names to be used, which will allow the names to be retired.

## Season effects

A table of the storms that formed during the 2005 Atlantic hurricane season is given below: it includes storm name, duration, peak strength, areas affected, damage, and death total. Damage and deaths include amounts while the storm was extratropical, a wave, or a low. The death toll includes all indirect deaths, such as traffic accidents or electrocutions. Damage figures are in 2005 USD.

## See also

- Tropical cyclones in 2005
- 2005 Pacific hurricane season
- 2005 Pacific typhoon season
- 2005 North Indian Ocean cyclone season
- South-West Indian Ocean cyclone seasons: 2004–05, 2005–06
- Australian region cyclone seasons: 2004–05, 2005–06
- South Pacific cyclone seasons: 2004–05, 2005–06
- Mediterranean tropical-like cyclone

Hurricane season in the Atlantic Ocean

Articles which contain graphical timelines