Tornado outbreak in southeast US
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A widespread and deadly tornado outbreak affected the Southeastern United States on Easter Sunday and Monday, April 12–13, 2020. Several tornadoes were responsible for prompting tornado emergencies, including the first one to be issued by the National Weather Service in Charleston, South Carolina. A large squall line formed and tracked through the mid-Atlantic on April 13, prompting more tornado warnings and watches. A total of 15 watches were produced during the course of the event, two of which were designated Particularly Dangerous Situations.
Throughout the two-day outbreak, a total of 141 tornadoes touched down across 10 states, inflicting widespread and locally catastrophic damage. The outbreak ranks 4th for producing the most tornadoes in a 24-hour period, with 132 tornadoes occurring between 14:40 UTC April 12–13; that tally is surpassed only by the Tornado outbreak of March 31 – April 1, 2023 with 134, the 1974 Super Outbreak with 148 and the 2011 Super Outbreak with 219. The strongest tornado of the outbreak occurred in Southern Mississippi, and was given a high-end EF4 damage rating after producing estimated winds of , reaching a width of , and causing eight deaths. With a total of 32 tornado-related fatalities, the Easter outbreak was the deadliest tornado outbreak since April 27–30, 2014. To assist with recovery efforts, governors of five states declared a state of emergency. Relief efforts were complicated by social distancing requirements amid the COVID-19 pandemic.
Meteorological synopsis.
Background.
For weeks throughout March and into April, an expansive area of high pressure built across the Southeast United States, contributing to abnormally warm temperatures across much of the country. The United States as a whole experienced its seventeenth warmest March, continuing the pattern that persisted throughout winter. In particular, many locations along the U.S. and Mexican Gulf coasts saw record warmest temperatures for the month. Calm weather associated with the high-pressure area induced rapid warming of the Gulf of Mexico waters to their highest values in the modern record—greater than above the 1971–2010 average—as well as a moistening of the air near the surface. Increased instability associated with anomalously warm and moist air from the Gulf of Mexico has been associated with an increased risk of severe weather and tornado activity.
April 12.
The first indications of organized severe weather came on April 8, when the Storm Prediction Center (SPC) outlined 15% probabilities for severe weather within of a point from central Texas eastward into the Florida Panhandle and eastern Georgia valid for April 11–12. These threat areas were later refined with the introduction of a day-3 moderate risk, the fourth of five threat levels, across northeastern Louisiana through central Alabama on April 10. Historically, the SPC issues one day-3 moderate risk every year, and half of those over the previous decade were later upgraded to High risk, the highest threat level. Over subsequent days, a significant mid-level shortwave trough progressed eastward across the United States. By the pre-dawn hours of April 12, mid-level cooling associated with the feature overspread the Edwards Plateau, Hill Country, and much of central Texas. Accordingly, an intense line of severe thunderstorms developed along a dry line while vigorous convective development formed farther east. These thunderstorms were initially isolated in nature but soon coalesced into a mesoscale convective system as they encountered an enhanced corridor of warm air streaming northward, as well as very strong wind shear. These initial storms produced scattered weak tornadoes in Texas during the early stages of the outbreak. This storm complex progressed across northern Louisiana through the late morning and early afternoon hours, and embedded circulations within the line began producing strong tornadoes, contributing to multiple tornado debris signatures visible on radar. The first strong tornado as well as the first one to cause casualties was in Desoto Parish, where an EF2 tornado destroyed manufactured homes and damaged trees and homes, injuring two people. The first intense and notable tornado was an EF3 tornado that triggered a tornado emergency as it moved through downtown Monroe, and damaging or destroying numerous homes, but there were no casualties. To the north, a second EF3 tornado near Sterlington caused extensive tree damage. In advance of the line, a lifting warm front aided in the formation of a very moist, highly unstable, and highly sheared environment across northeastern Louisiana and much of Mississippi. Accordingly, the SPC issued a particularly dangerous situation tornado watch into the late evening hours.
A weather balloon launch from Jackson, Mississippi, at 18:00 UTC revealed the presence of a capping inversion across the region. This cap was expected to weaken across central Mississippi, while forecasters expressed more uncertainty about its longevity across southern Mississippi and Louisiana. As a small area of low pressure progressed across northwestern Mississippi, it caused surface winds to turn out of the east-southeast, enhancing the potential for tornadoes. As a cluster of storms across central Mississippi progressed toward the northeast, it began to reintensify and develop embedded supercell characteristics with an attendant threat of strong tornadoes. Farther south, two distinct supercells developed within an environment where long-tracked, significant tornadoes were favored, both exhibiting extremely strong rotation and distinct debris signatures. Based on previous storm structures in similar environments, the SPC remarked that "this is an exceptionally rare event" and estimated tornadic winds of on the first supercell, consistent with a tornado of EF4 or EF5 intensity. After conducting damage surveys, meteorologists identified two violent tornadoes with the first supercell, one that killed four people and injured three others near Sartinville to southwest of Bassfield, and a second that killed eight people and injured 95 others from south of Bassfield to Pachuta, both of EF4 intensity. A long-tracked EF3 tornado was identified with the second supercell that tracked behind the first one, producing significant damage near Oak Vale and Carson, injuring two people. The first supercell also produced two other tornadoes after the second EF4 tornado dissipated, including an EF2 tornado that passed near Stonewall and Enterprise that destroyed a mobile home and heavily damaged a home and a church, and snapped numerous trees. The second supercell also produced a tornado, which was rated EF1, as it passed Enterprise. Both supercells then weakened and merged with a squall line after that.
Throughout the evening hours, the severe weather and tornado risk shifted eastward into Alabama, as the initial cluster of severe storms with numerous embedded semi-discrete supercells and comma-head circulation moved across north-central Alabama, contributing to multiple strong tornadoes. This included a damaging rain wrapped EF2 tornado that struck a residential area at the southwestern outskirts of Boaz, injuring three people. Later, a high-end EF1 tornado caused major damage and three injuries in Carbon Hill. This feature continued into northwestern Georgia, maintaining its well-defined structure in spite of a marginally unstable environment. In the end, this complex produced 43 tornadoes alone, including nine rated EF2 and two rated EF3. A high-end EF2 tornado spawned by an isolated supercell thunderstorm ahead of the main complex carved a path northwest of Chatsworth, Georgia and through the small community of Sumac, killing eight people and injuring 24 others. While local enhancement of storm activity occurred within an extensive line of convection in central Alabama, dewpoints rose in the wake of the earlier storm complex across northern Georgia and southeastern Tennessee, further boosting instability values in the presence of extremely strong wind shear. An EF3 tornado embedded within the main line of storms killed two people and injured 18 others in the eastern suburbs and neighborhoods of Chattanooga, Tennessee. The same storm also produced an EF2 tornado that damaged or destroyed numerous homes and mobile homes in eastern Cleveland, Tennessee, injuring six people.
April 13.
During the early-morning hours of April 13, the pre-frontal squall line shifted eastward into eastern Georgia and the Carolinas, with numerous well-organized embedded supercells forming within the line, producing numerous tornadoes across the region in an event known as the Central Savannah River outbreak. An EF1 tornado passed through Cartersville, Georgia, killing one person when a tree fell on a house while causing two additional injuries elsewhere. An EF3 tornado that damaged or destroyed multiple homes was confirmed south of Thomaston to northwest of Redbone, Georgia, with one home being pushed off its foundation and into the middle of a road. The same circulation produced another EF3 tornado near Forsyth, injuring one person and damaging or destroying numerous structures and vehicles, including aircraft. A third EF3 tornado from south-southeast of Westminster to west of Central, South Carolina in South Carolina killed one person and caused major damage in Seneca. Yet another EF3 tornado tracked from east-northeast of Elko to west-southwest of St. Matthews in South Carolina and caused two more fatalities. The most significant tornado to occur on April 13 was a multiple-vortex EF4 tornado that killed five people near the South Carolina towns of Estill and Nixville. This tornado was part of a tornado family that produced 12 tornadoes, including an EF1 tornado that killed one person in Walterboro. A total of eight separate EF3 tornadoes were confirmed across Georgia and South Carolina during this portion of the outbreak. Through the late morning hours of April 13, the line of intense thunderstorms continued eastward and intensified given marginal daytime heating, a steady stream of rich moisture, and intense low-level wind shear. The SPC had already outlined an Enhanced risk of severe weather along the U.S. East Coast from southeastern Georgia northward into northern Virginia and damaging winds and tornadoes were reported until the storms moved offshore. Later, more severe storms formed over the Appalachian Mountains and moved into the Northeast megalopolis, where a Slight risk had been issued. These storms produced large swaths of damaging winds and two weak tornadoes throughout this area for the rest of day until the outbreak came to an end.
Confirmed tornadoes.
Monroe, Louisiana.
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The first notable tornado of the outbreak touched down south-southwest of Brownsville-Bawcomville, Louisiana at 11:36 a.m. CDT (16:36 UTC). It moved northeast at EF1 strength, snapping or uprooting numerous trees at the intersection of Brown Street and Evergreen Street and in neighborhoods to the northeast as the tornado moved toward Monroe, with several trees landing on homes. A metal building had its overhead door blown out, several manufactured homes along Sandal Street were damaged, and a trailer was tipped over along LA 34. The tornado then reached EF2 strength as it moved into West Monroe, snapping power poles in this area, breaking metal trusses at a paper mill, and blowing over a wood chip conveyor belt. Maintaining EF2 intensity, the tornado crossed the Ouachita River two times, and impacted Riverbend Drive. In this area, many trees were snapped, a home lost its roof, and another home sustained partial wall collapse. The tornado then crossed the Ouachita River a third time and impacted neighborhoods along Business US 165 and LA 15 to the south of downtown Monroe, where a tornado emergency was issued due to a large debris ball showing up on radar. Multiple homes in this area had roofs torn off and a few of them also sustained some collapse of exterior walls. A large two-story home lost all of its roof, and an art museum also had severe roof damage. Numerous other homes in this area sustained roofing and window damage, and many trees and power poles were downed. Continuing northeast of Railroad Avenue, the tornado momentarily weakened to EF1 intensity as moved through additional residential areas, downing more trees and damaging the roofs of homes. Regaining EF2 strength, the tornado crossed I-20 at US 165, heavily damaging a metal building and snapping several power poles along LA 594. The tornado then reached its peak intensity as several well-built homes in a subdivision along Orchid Drive had roofs ripped off and multiple exterior walls collapsed, and numerous other homes sustained varying degrees of damage. Peak damage in this subdivision ranged from high-end EF2 to low-end EF3. Sporadic EF1 damage was observed as the tornado proceeded to cross Powell Avenue, where homes sustained partial roof loss and trees were damaged. Northeast of this area, the tornado strengthened back to EF2 intensity as it completely destroyed a metal hangar at Monroe Regional Airport. A large metal building was also heavily damaged in this area before the tornado abruptly lifted and dissipated as it crossed an airport runway at 11:45 a.m. CDT (16:45 UTC).
The tornado lasted for