The India Meteorology Department has issued the preliminary report on Severe Cyclonic Storm “Nisarga” over Arabian Sea during 1st-4th June, 2020. According to the report, the salient features of the system are described below:
Brief Life History:
• The severe cyclonic storm, Nisarga originated from a Low Pressure Area which formed over southeast & adjoining eastcentral Arabian Sea and Lakshadweep area in the early morning of 31st May 2020.
• It intensified into deep depression over eastcentral Arabian Sea in the early morning and into cyclonic storm “NISARGA” in the noon of 2nd June.
• Continuing to move northeastwards, it crossed Maharashtra coast close to south of Alibag as a Severe Cyclonic Storm (SCS) with a maximum sustained wind speed of 110-120 kmph gusting to 130 kmph during 0700-0900 UTC (1230-1430 hrs IST) of 03rd June.
• Continuing to move northeastwards after landfall, it weakened into a cyclonic storm in the evening over north Madhya Maharashtra and into a deep depression in the mid-night of 2nd June 2020 over the same region.
• It lay as a low pressure area over southeast Uttar Pradesh and adjoining Bihar in the afternoon 5th June.
• The last cyclone, which crossed Maharashtra coast was cyclonic storm, Phyan which crossed coast on 11th Nov., 2009. Prior to the SCS, Nisarga, an SCS crossed Maharashtra coast on 24th May, 1961. It was also the fourth cyclone crossing Maharashtra coast during the 1961-2020.
Monitoring of NISARGA:
India Meteorological Department (IMD) maintained round the clock watch over the north Indian Ocean and the development of the system was monitored since 21st May, about 10 days prior to the formation of low pressure area over the southeast & adjoining eastcentral Arabian Sea and Lakshadweep area on 31st May. The cyclone was monitored with the help of available satellite observations from INSAT 3D and 3DR, SCAT SAT, polar orbiting satellites and available ships & buoy observations in the region. The system was also monitored by Doppler Weather RADARs (DWR) Goa and Mumbai. Various numerical weather prediction models run by Ministry of Earth Sciences (MoES) institutions, models run by other Global centres and dynamical-statistical models were utilized to predict the genesis, track, landfall and intensity of the cyclone. A digitized forecasting system of IMD was utilized for analysis and comparison of various models’ guidance, decision making process and warning products generation.
i) Genesis Forecast
• First information about development of low pressure area over southeast Arabian Sea was given in the extended range outlook issued on 21st May about 10 days prior to the formation of low pressure area over the southeast & adjoining eastcentral Arabian Sea and Lakshadweep area on 31st May.
• First information about development of depression over southeast Arabian Sea was issued in the tropical weather outlook and national weather forecast bulletin issued at 1200 noon of 29th May about 3 days prior to the formation of depression over southeast & adjoining eastcentral Arabian Sea on 1st June morning.
ii) Cyclone warnings
• Pre-cyclone watch: Considering the expected short life of the system and it’s intensification into a cyclonic storm with predicted landfall over north Maharashtra and south Gujarat coasts on 3rd June the Pre cyclone watch was issued for north Maharashtra and south Gujarat coasts in the bulletin issued at 0830 UTC (1400 hrs IST) of 31st May, when the system was a low pressure area over southeast and adjoining eastcentral Arabian Sea, even before the development of depression (about 80 hours prior to landfall of SCS NISARGA). This is for the first time that Pre cyclone watch was issued by IMD in the low pressure area stage. Usually, the pre cyclone watch is issued from depression/deep depression stage as per the Standard Operating Procedure.
• Cyclone Alert: Cyclone alert was issued for north Maharashtra and south Gujarat coasts in the bulletin issued at 1150 hrs IST of 1st June, when the system was a depression over eastcentral Arabian Sea and neighbourhood (about 50 hours prior to landfall of SCS NISARGA).
• Cyclone Warning: Cyclone warning was issued for north Maharashtra and south Gujarat coasts in the bulletin issued at 0900 UTC (1430 hrs IST) of 2nd June, when the system was a cyclonic storm over eastcentral Arabian Sea (about 24 hours prior to landfall of SCS NISARGA).
• Post landfall outlook: Post landfall outlook indicating expected severe weather over interior districts of Maharashtra was given in the bulletin issued at 2150 hrs IST of 2nd June, when the system was a cyclonic storm over eastcentral Arabian Sea (about 16 hours prior to landfall of SCS NISARGA).
iii) Track, landfall and intensity forecast
From the first bulletin issued at 0330 UTC (0855 hrs IST) of 31st May, indicating that the system would intensify into a cyclonic storm and reach north Maharashtra and Gujarat coasts by 3rd June, till the bulletins issued on 3rd June, when actually, the severe cyclonic storm Nisarga crossed north Maharashtra coast close to south of Alibagh with a maximum sustained wind speed of 110-120 kmph gusting to 130 kmph between 0700-0900 UTC (Afternoon) of 03rd June, the track, landfall point & time, intensity and associated adverse weather like heavy rainfall, gale wind and storm surge were well predicted by IMD.
India Meteorological Department (IMD) and RSMC New Delhi duly acknowledged the contribution from all the stake holders and disaster management agencies who contributed to the successful monitoring, prediction and early warning service of SCS NISARGA.
Main Fig.: Observed track of SCS ‘NISARGA’ over the eastcentral and adjoining southeast Arabian Sea (1st-4th June, 2020)
Kindly visit www.imd.gov.in for updates.