IMD releases its Weather Status for May, 2020 & its verification and Outlook for next four weeks (05 June to 02 July, 2020)

New Delhi, June 17, 2020: The India Meteorological Department (IMD) has released its Weather Status for May, 2020 & its verification and Outlook for next four weeks (05 June to 02 July, 2020). According to this:

Significant Features of May, 2020

Super Cyclonic storm “AMPHAN”:                                                                             

  • The Super Cyclonic Storm (SuCS) “AMPHAN” originated from the remnant of a Low Pressure Area (LPA) which occurred in the near Equatorial Easterly wave trough over south Andaman Sea and adjoining southeast Bay of Bengal (BoB) during 1st – 5th May. Though the LPA had become less marked on 6th May, its remnant circulation meandered over south Andaman Sea and adjoining southeast BoB during 6th – 12th May. Under its influence, a fresh LPA formed over southeast BoB and adjoining south Andaman Sea in the morning (0830 IST) of 13th May.
  • Under favourable environmental conditions, it concentrated into a depression (D) over southeast BoB in the early morning (0530 IST) of 16th May and further intensified into a deep depression (DD) in the afternoon (1430 IST) of the same day. It moved north- northwestwards and intensified into the cyclonic storm “AMPHAN” (pronounced as UM-PUN) over southeast BoB in the evening (1730 IST) of 16th May, 2020. Moving nearly northwards, it further intensified into a severe cyclonic storm (SCS) over southeast BoB in the morning (0830 IST) of 17th May. It underwent rapid intensification during subsequent twenty four hours and accordingly intensified into a very severe cyclonic storm (VSCS) by the afternoon (1430 IST) of 17th, extremely severe cyclonic storm (ESCS) in the early hours of 18th (0230 IST) and into a super cyclonic storm (SuCS) around noon (1130 IST) of 18th May, 2020. It maintained the intensity of SuCS over westcentral BoB for nearly 24 hours (during 1130 IST of 18th-19th), before weakening into an ESCS over westcentral BoB around noon (1130 IST) of 19th May. Thereafter, it weakened slightly and crossed West Bengal – Bangladesh coasts as a VSCS, across Sundarbans, near latitude 21.65°N and longitude 88.3°E during 1530-1730 hrs IST of 20th May, with maximum sustained wind speed of 155 – 165 kmph gusting to 185 kmph. Moving north-northeastwards, it weakened into an SCS over Bangladesh & adjoining West Bengal around mid-night (2330 IST) of 20th May, weakened further into a CS over Bangladesh in the early hours (0230 IST) of 21st May, into DD over Bangladesh around noon of 21st May and into a D over north Bangladesh in the evening (1730 IST) of the same day. The observed track of the system during 16th – 21st May is presented in Annexure I.

 

  • The system caused heavy to very heavy rainfall at a few places over coastal Odisha & Gangetic West Bengal on 20th May, heavy rainfall at isolated places over Gangetic West Bengal & adjoining Bangladesh and Assam, Meghalaya & Arunachal Pradesh on 21st May and heavy rainfall at isolated places over Assam, Meghalaya, Arunachal Pradesh, Sikkim, Nagaland, Manipur & Mizoram on 22nd May. Kolkata (Dum Dum) reported 130 kmph at 1855 hrs IST and Kolkata (Alipore) 112 kmph at 1752 hrs IST of 20th May. As per the post cyclone landfall survey conducted by ACWC Kolkata, tidal waves of 15 feet height inundated low lying areas of the coastal Districts of West Bengal.
  • The landfall point forecast errors for 24, 48 and 72 hrs lead period were 5.5, 11.0, and 37.4 km respectively against the Long Period Average errors of 44.7, 69.4 and 109.3 km during 2015-19 respectively. The landfall time forecast errors for 24, 48 and 72 hrs lead period were 0.5, 0, and 2.0 hours respectively against the LPA errors of 3.0, 5.4 and 8.6 hours during 2015-19 respectively. The track forecast errors for 24, 48 and 72 hrs lead period were 59.4, 59.9, and 61.0 km respectively against the LPA errors of 80.6, 125.5, and 171.2 km respectively. Track forecast errors were exceptionally less than the past five years average errors for all lead periods. Similarly, track forecast skill was higher than the past five years average skill for all lead periods beyond 24 hours. In addition, all the three types of weather like heavy rainfall, gale wind and storm surge were well predicted. A total of 48 national bulletins were issued including 3 informatory messages.

Advance of Southwest Monsoon 2020:

All the criteria for onset of Monsoon had been satisfied over Nicobar Islands on 17 May 2020 and IMD had declared onset of monsoon in some parts of south Bay of Bengal, Nicobar Islands & Andaman Sea. The Northern Limit of Monsoon (NLM) passed through Lat.5°N/Long.85°E, Lat.8°N/Long.90°E, Car Nicobar,Lat.11°N/Long.95°E on 17th May  2020. Further advance happened aftermore than a week and accordingly Southwest Monsoon advanced into some more parts of South Bay of Bengal, most parts of Andaman Sea and Andaman & Nicobar Islands on 27th May 2020 and the NLM passed through Lat.5°N/Long.82°E,Lat.7°N/Long.86°E, Lat.10°N/Long.90°E, Port Blair, and Lat.15°N/Long.97°E on that day. It has further advanced into some parts of Maldives-Comorin area, some more parts of south Bay of Bengal, remaining parts of Andaman Sea and Andaman & Nicobar Islands on 28th May 2020 and the NLM passed through Lat.5°N/Long.72°E, Lat.6°N/Long.79°E, Lat.8°N/Long.86°E, Lat.11°N/Long.90°E, Lat.14°N/Long.93°E and Lat.16°N/Long.95°E on that day. It has further advanced into some parts of Southwest and Southeast Arabian Sea and some more parts of Maldives-Comorin area on 29th May 2020 and the NLM passed through Lat.7°N/Long.50°E, Lat.7°N/Long.60°E, Lat.7°N/Long.70°E, Lat.6°N/Long.75°E, Lat.6°N/Long.79°E, Lat.8°N/Long.86°E, Lat.11°N/Long.90°E, Lat.14°N/Long.93°E and Lat.16°N/Long.95°E on that day. There had been no further advance during the remaining two days hence the NLM remained like that till the end of the month. Advance of NLM till 31 May 2020 is shown in Annexure II.

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