With a La Nina or a cooling of the central Pacific Ocean expected to firmly take root in September, the India Meteorological Department (IMD) has forecast a rainy September with several parts of north India forecast to receive heavy rainfall.
While the monsoon is expected to start retreating in September, the impact of the La Nina is likely to lead to vigorous “cyclonic activity” in the Bay of Bengal and consequently several episodes of rain for most of the month, Mrutunjay Mohapatra, Director General, IMD, said at a press conference on Saturday. Monsoon rainfall in September is expected to be 9% above what is usual for the month (16.8 cm). Given that monsoon rainfall is unequally distributed, this would mean that many parts of Rajasthan, Uttarakhand, and Delhi are likely to see heavy rains, according to the IMD’s forecast maps. “The monsoon withdrawal usually begins by mid-September but with heavy rainfall expected, it is too early to forecast it as of now,” Dr. Mohapatra said.
Rainfall in August also turned out to be much more than the IMD had anticipated at the beginning of the month. The forecast was for rainfall in August — the second rainiest of the monsoon months — to be 6% more than normal rainfall but India ended up getting 15% more than normal rainfall. “A feature of the monsoon during August this time was that there were no major ‘breaks’ and several low pressure systems (moisture laden winds blowing in the surrounding ocean) formed. It is not possible to predict these, as of now, much in advance,” he added. Six low pressure systems formed during August.
Weather models used by the IMD to forecast rainfall over the next week or two have higher accuracy, and suggest that at least four cyclone precursors are expected to form in the next month.
Meanwhile, the cyclonic storm Asna has moved away from the Gujarat coast and continues to hover in the north-central Arabian Sea. It is expected to dissipate by September 2.
A depression that has formed over the northwest Bay of Bengal is likely to cross northern Andhra Pradesh late on Saturday but without becoming a cyclone, the IMD added.
