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Monsoon to have an extended stay of 8 days over the city
The southwest monsoon will have an extended stay of eight days over Mumbai, the Indian Meteorological Department (IMD) stated on Wednesday.
The southwest monsoon will have an extended stay of eight days over Mumbai, the Indian Meteorological Department (IMD) stated on Wednesday.
The normal onset date has been delayed by a day and withdrawal date by nine days, stated IMD in its monsoon forecast. The new onset date for Mumbai is June 11 (against June 10 originally) and the new withdrawal date has been declared as October 8 (against the existing September 29). This means that the normal duration of the entire monsoon over Mumbai will span from June 11 to October 8 across 120 days as opposed to 112 days from June 10 to September 29.
“Existing dates were so far based on old data from 1901-1940. We have revised this based on data from 1961-2019 for onset dates and 1971-2019 for withdrawal dates. Earlier, the data was collated from 149 stations. The new dates are based on data from 3,500 stations across India,” said Mrutyunjay Mohapatra, IMD’s director-general. “Based on this, Mumbai’s normal monsoon duration has increased by over a week (eight days),” he added.
Across the state, new monsoon advance dates have been delayed by three to seven days while major changes have been identified for withdrawal dates. For example, the onset date for Jalgaon has changed from June 13 to June 18 while the withdrawal is October 6 from September 27. Changes for seven Maharashtra cities were published by IMD on Wednesday. “We cannot go by weather information that was relevant almost 80 years back and that change is visible in monsoon behaviour over the past decade. Climate change has a major role but its exact impact on monsoon is yet to be studied,” said Mohapatra.
Delay in monsoon withdrawal by around 10 days is likely to impact the agriculture sector, especially across central Maharashtra, Vidarbha and Marathwada, said Akshay Deoras, Independent meteorologist and Ph.D. researcher at the University of Reading, UK. “Significant rainfall activities beyond mid-September can have a negative impact for crop harvesting. Maharashtra has already seen significant damages to ready to harvest or harvested crops in October in the last few years. The state government needs to come up with an action plan for this,” he said.
On Wednesday, IMD released its first stage country-wide long-range forecast for the southwest monsoon (June to September) 2020, which is expected to be ‘normal’ or 100% of the long period average (LPA), with a model error of ± 5%. India defines ‘normal’ rainfall as between 96% and 104% of a 50-year average of 88 cm for four-months.
“This is good news as it benefits the agricultural sector, food and water security during this difficult period of the Covid-19 outbreak,” said M Rajeevan, secretary, Ministry of Earth Sciences (MoES) adding that the forecast was based on models predicting favourable ocean-atmospheric global weather factors.
There is a 41% probability that the monsoon will be 96-104% (normal) and a 21% probability that it may be 104-110% (above normal). Last year too, the forecast was 96%, but actual rainfall was 110% of the LPA, the highest since 1994. IMD will be releasing its second stage forecast during the last week of May or June first week.
HT had reported on April 13 that Mumbai city and suburbs could witness above average rainfall (2,500 mm) this monsoon, more than the seasonal average, as per forecasts issued by independent meteorologists.
Meanwhile, private weather forecasting agency Skymet will not be issuing its forecast this year. The agency was widely criticised for their inaccurate forecast last year. “This was a decision taken by our management. The weather patterns and dynamics are changing and we want to invest in our technology so that we come on top and give an accurate forecast. We will be back next year with better technology backed updates,” the agency said in a statement.
