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Cyclone Yaas

North Indian Ocean cyclone in 2021

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Through Bangladesh and India

In preparations for the storm, many electrical companies in West Bengal and Odisha prepared additional generators and transformers for possible electrical problems. Evacuations were also ordered, starting on 24 May on low-lying areas in East Midnapore and West Midnapore and Jhargram. Hooghly, Kolkata and North 24 Parganas and South 24 Parganas are now placed on high alert. Railway operations and marine activities were halted due to Yaas, while rescue authorities and medical teams were deployed in for possible emergencies. In Bangladesh, over two million individuals were ordered to be evacuated in coastal areas of the country due to the storm's approach. Food supplies and emergency funds were also released for the evacuees. 20 people across India and Bangladesh died due to Yaas. West Bengal was the hardest hit Indian state, with an estimated loss of ₹210 billion (US$2.89 billion). Odisha also suffered a loss of ₹6.1 billion (US$83.9 million).

Meteorological history

On 22 May, a low-pressure area formed in the Bay of Bengal. On the next day, at 09:30 UTC, the disturbance intensified into a depression and was assigned the designation BOB 02 by the India Meteorological Department (IMD). Meanwhile, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) at 15:00 UTC on 22 May on the developing system. The system subsequently intensified into a deep depression at 15:00 UTC on 23 May. On the following day, at 02:30 UTC, the system further intensified into a cyclonic storm and was given the name Yaas by the IMD. At that time, the low-level circulation centre of the system became partially-exposed due to moderate wind shear; however, large masses of rainbands persisted in the southern portion of the storm as it remained in a marginally favourable environment for intensification, with warm sea surface temperatures and good outflow but moderate wind shear. The IMD further upgraded Yaas to a severe cyclonic storm at 18:00 UTC that day as the system became more organised. A subtropical ridge turned the system northeast into an area of low wind shear, causing Yaas to gradually strengthen. At 12:00 UTC on 25 May, the JTWC upgraded the storm to a Category 1 system as the system further organised. Despite Yaas being negatively affected after making landfall, combined with the weakening effects of moderate wind shear and poor outflow, it intensified further to a very severe cyclonic storm at 15:00 UTC on 25 May as it featured a profound convection. The storm subsequently reached its peak intensity of 140 km/h (85 mph) in three-minute sustained wind speeds, according to the IMD; the JTWC had slightly lower estimates of 120 km/h (75 mph) on the system. Around 09:00 IST (03:30 UTC) on 26 May, Yaas made landfall north of Dhamra Port and south of Bahanaga at the same intensity. Upon moving inland, the JTWC issued their final warning on the storm as it weakened to a tropical storm since it was over land and also faced increased vertical shear. Soon afterward, the IMD also discontinued advisories as the system became disorganised and as it weakened to a deep depression. Yaas eventually dissipated in northern India on 28 May.

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