IMD may tweak 2020 monsoon onset date, forecast above-average rain

There is also a likelihood that the weather bureau may forecast above-normal monsoon rain for India this year due to a likely transition to La Nina from a weak El Nino, officials said. La Nina, or cooler-than-usual sea surface temperatures in the east-central Pacific Ocean, is typically associated with better monsoon rains and colder winters in India while El Nino is associated with below-normal rainfall in the country.

El Nino and La Nina events tend to develop during Apr-Jun and reach their maximum strengths during Oct-Feb, the International Research Institute for Climate and Society of the Columbia University said. Such weather events typically persist for nine months to a year. Currently, the official date for onset of southwest monsoon is Jun 1 and the withdrawal date is Sep 30. However, in recent years, the monsoon current has been hitting the mainland much after Jun 1. The withdrawal date of the monsoon current has also seen delays. In 2019, the southwest monsoon hit the Kerala coast on Jun 8, while it withdrew from the mainland on Oct 16. At the same time, the monsoon current hits different parts of the country on different dates, which is reviewed by a committee set up by the weather bureau almost a decade ago, which speciifically looks at the onset dates over the central and northern regions. The forecast would be released through online video conferencing, as part of the social distancing measures adopted by the government to control the spread of COVID-19 pandemic.