Pacific typhoon in 2021
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Typhoon In-fa, known in the Philippines as Typhoon Fabian, was a very large and costly tropical cyclone that brought record amounts of rainfall to China in late July 2021, becoming the second-wettest tropical cyclone ever recorded in the country. It was also the first storm to impact the city of Shanghai since Typhoon Mitag of 2019. The ninth depression, sixth tropical storm and third typhoon of the 2021 Pacific typhoon season, the system was first noted by the Joint Typhoon Warning Center as an area of low pressure, located east of the Philippines on July 14. Favorable conditions helped the storm to intensify, becoming a tropical depression, two days later and a tropical storm on July 17, being assigned the name "In-fa" by the Japan Meteorological Agency. Located in a weak steering environment, the system struggled to organize under dry air and moderate wind shear before organizing further. It continued to move mostly westward, strengthening into a typhoon and deepening quickly. The storm struggled to organize itself significantly due to continuous dry air intrusions and its frequent motion changes. On July 21, it reached its peak intensity according to the JTWC with winds of ; the JMA estimated a lower numbers of on the system. Nevertheless, the system reached its minimum barometric pressure of , three days later after passing through the Ryukyu's. As the system entered the East China Sea, marginal conditions started to take toll on the system, with In-fa weakening steadily and slowly, until it made its consecutive landfalls over Putuo District of Zhoushan and Pinghu on July 25 and 26, respectively, as a tropical storm. For the next couple of days, the storm slowly moved inland while gradually weakening, before turning northward on July 29. Later that day, In-fa weakened into a remnant low over northern China. The remnants continued their northward trek for another couple of days, before dissipating near North Korea on July 31.
In-fa caused rough waves along the Japanese islands, along with torrential rainfall and high winds, highly damaging and downing many structures, killing one person. The Philippines experienced flooding due to heavy rainfall, and some winds, resulting in the death of five people. China experienced widespread impacts in agriculture, infrastructure, transportation, and other areas. The typhoon brought flooding rainfall and storm surge to a large area, with some regions experiencing nearly a month's worth of rainfall in just one to two days. Rivers overflowed and some floodwaters were up to the roofs of cars.
The storm exacerbated and played a part in starting the 2021 Henan floods, killing at least 302 people and dealing upwards of 82 billion yuan (US$12.7 billion) in damage. At least 50 are missing. The typhoon itself has caused at least $2 billion in damages and 6 deaths.
Meteorological history.
Origins.
At 06:00 UTC of July 14, the Joint Typhoon Warning Center (JTWC) started to monitor a persistent area of convection, roughly associated with a low-level circulation center, located west-northwest of Guam. The disturbance was located in an environment conducive for tropical cyclogenesis, with warm sea surface temperatures and good equatorial outflow due to a favorable configuration of an upper low over the western part of the mainland Japan and a tropical upper tropospheric trough (TUTT) to the northwest. Later, it moved through an area of moderate wind shear which made the system's LLC broad while moving west-northwestward: the wind gradient slowly became conducive for the disturbance to slowly intensify. At 20:30 UTC of the next day, the agency upgraded the system's potential trend of intensification to "high" and issued the disturbance's Tropical Cyclone Formation Alert (TCFA).
At 00:00 UTC, the Japan Meteorological Agency (JMA) upgraded the disturbance to a depression, followed by the PAGASA's designation of the system as "Tropical Depression Fabian" as it was now inside of the Philippine Area of Responsibility, being the sixth tropical cyclone in the region in the season, three hours later and the JTWC at 09:00 UTC. Located in a complex steering environment, the storm resembled a monsoon depression at that time while moving slowly northwestward before turning northward, both steered by the western periphery of a deep-layered subtropical ridge to the east. Later, a pocket of dry air from the western semicircle and upper-level westerlies disrupted the system, with the LLC becoming broad and exposed while slowly and steadily intensifying, with the evidence of cooling cloud tops. In addition, the depression was being moved northwestward by a compound monsoon gyre pattern and at the same time, a near-equatorial ridge before being guided by another subtropical ridge to the east of Honshu, still caught under a weak steering flow. Four hours later, the PAGASA further designated Fabian to a tropical storm and being followed by the JMA at 18:00 UTC that day, being assigned the name "In-fa". The JTWC did the same at 03:00 UTC on July 18, with the storm remaining slow in motion due to now-weakening westerlies. The PAGASA, meanwhile, reported that the system further intensified to a severe tropical storm at that time. Although the low-level circulation center remained exposed while moving to the north-northwest, animated multispectral imageries on that day revealed a well-defined LLC with a symmetric area of large convection on the western edge and further centered on the central core.
Intensification.
The large size of In-fa, combined with the continuous dry air entrainment, together restrained the system's rapid development over the warm waters of the Philippine Sea; however, as the storm continued its trajectory towards the Ryukyu Islands, the curved banding of the system further consolidated on its and a microwave eye feature started to emerge. At the same time, the system began to take a northwest track before moving west-northwestward under a subtropical ridge over Japan by the early hours of July 19. At 00:00 UTC that day, the JMA further upgraded In-fa to a severe tropical storm. The system, decelerates again as it started to impact the Ryukyu's, with In-fa's convection or thunderstorms deepening and an eye further appearing. Six hours later, the PAGASA reported in their bulletins that In-fa further became a typhoon, while located approximately 895 kilometres to the east of extreme Northern Luzon. The JTWC followed suit at 09:00 UTC that day and the JMA, three hours later. As it passed south of Daito Islands, a eye was further evident on satellite imageries, which later shrunk; however, In-fa remained a high-end Category 1 system as it started to move westward and later, a west-southwest track. As the eye started to enlarge again, with the Dvorak countings of T4.5-T5.0, the JTWC further upgraded In-fa to a mid-level Category 2 typhoon at 03:00 UTC on July 21 with winds of ; this made the system's peak intensity according to the JTWC's estimates.
Radar imagery from Okinawa Island showed a large and clear eye, though at the same time, another satellite imagery revealed an eyewall that was disrupted due to continuous dry air intrusions while moving westward. Later, as it shifted its motion west-southwestward, In-fa's eye became ragged due to another intrusion of dry air. Furthermore, dry northerlies suppressed the system as it dived southward. At 03:00 UTC of the next day, In-fa started an eyewall replacement cycle while its northern quadrant started to weaken as it changed its motion yet again to the south-southwest. In addition, the system is being steered by the southern periphery of a high-amplitude ridge over the Sea of Japan. Six hours later, the typhoon started to weaken with its eye expanding and weakening banding on the system while tracking westward and further, northwestward at a slow motion rate. Its steering movements were caused by a subtropical ridge to the north and another one over the east coast of North Korea. As it continued to approach the Ryukyus while traveling from the northwest, In-fa further weakened to a high-level Category 1 system due to continuous upwelling, its suppressed outflow and slowly cooling sea surface temperatures. By 15:00 UTC of July 23, In-fa passed between the Tarama Island and Miyako-jima Island, with its remaining large eye passing over the latter as it slightly shifted its movement towards the north-northwest. The system further degraded to a tropical storm according to the estimates of JTWC, six hours later as it slowly moved away from the Ryukyu Islands and the convection on the eye was not continuous while subsequently entering the East China Sea. By 03:00 UTC on the next day, In-fa reintensified to a low-end Category 1 system as it reformed its convective depths and continued to maintain a ragged eye while moving northward. Six hours later (23:00 PST of July 23), In-fa left the PAR, with the PAGASA issuing its last bulletin while located, 640 kilometres to the north-northeast of Itbayat, Batanes. The JMA then analysed that In-fa further reached its peak with maximum sustained winds of and a minimum barometric pressure of , three hours later.
China landfalls and demise.
In-fa started to move north-northwestward under the periphery of a mid-level ridge over the Sea of Japan as it started to remain at a low-end Category 1 intensity due to continuous marginal waters and upwelling. At 04:30 UTC on the next day, the system made its first landfall in the eastern Chinese province of Zhejiang, over Putuo District, a major port area in the city of Zhoushan. Four and a half hours later, the JTWC quickly downgraded the system to a tropical storm as its eye became ill-defined and the central dense overcast further became evident on satellite imageries instead of the former. The JMA, in the other hand reported that the storm weakened to a severe tropical storm in their analysis, another four hours later. Although tracking inland south of Shanghai, In-fa's overall structure remained compact and its gale-force winds further expanded, although as it reentered the East China Sea from Zhoushan, the core of the system slowly eroded. At 01:30 UTC of July 26, the large storm made its second coastal landfall over Pinghu, Jiaxing with maximum sustained winds of from the west-northwest. Shortly after the landfall, the JTWC discontinued warnings on In-fa as it had moved well inland, having no chances to redevelop. In their last warning on the system, the agency assessed the system as a weak tropical storm. Meanwhile, the JMA downgraded the system to a tropical storm by 12:00 UTC of that day due to further weakening of the storm by the means of land interaction. At 00:00 UTC of the next day, the JMA reported that In-fa further degraded to a tropical depression while moving west-northwest, with its center located at Shou County, Anhui Province. Over the next few days, it moved north and subsequently entered Shandong before turning north-northeast while subsequently slowing down. By 06:00 UTC of July 29, the system turned northward yet again before being further downgraded by JMA as a low-pressure area, twelve hours later as it shifted its movement northeastward. The remnants of In-fa entered the Bohai Sea later that night.
Preparations.
The threat of storm surge and high waves caused concern for those out at sea.
Japan.
In the Ryukyu Islands, the Okinawa Meteorological Observatory held a meeting on July 17 to discuss the storm, warning people to be cautious of the approaching system. Strong winds and heavy rains were also expected due to the storm. In addition, wave warnings were also issued by the JMA from different meteorological stations in the Japanese island group particularly in the islands of Okinawa, Miyako Islands and Amami Islands, while lightning and wind warnings was placed on Daitō Islands due to the approaching system. Later, sea warnings and alerts were imposed in these areas, including the East China Sea and further on the coastal areas of Kagoshima Prefecture and the island of Shikoku. Rainfall amounts up to were forecasted in the area, - in the main island of Okinawa and - in the Maejima Islands. The Sakishima Islands were forecast to get up to of rain.
A school in Kitadaitō, Okinawa was temporarily closed due to the storm while roadways on the village were shut down, starting on July 19. Marine activities in the area were also affected, with fishermen forced to tie their boats as they cannot fish due to In-fa. Sugarcane industries also feared that they will run out of food supply in their area due to the ongoing cancellation of vessels.