Back-to-back systems over the Bay could delay northeast monsoon

CHENNAI: Back-to-back low pressure systems expected over the Bay of Bengal could delay withdrawal of the southwest monsoon and push northeast monsoon onset to October-end early November. The southwest monsoon normally withdraws by October 15 and northeast monsoon sets in around October 20 with a deviation of seven days.
Prof Sridhar Balasubramanian, climate expert, IIT Bombay, said the monsoon trough is still active over central India as a low pressure area expected to form on October 9 is likely to enter central India and then west coast.Another low pressure area, from South China Sea, is likely to move into Bay of Bengal on October 15 and could enter central India. These systems are likely to reduce the number of active NE monsoon days for Tamil Nadu and south India.
A regional meteorological centre forecast said a fresh low pressure area is likely over north Andaman Sea and adjoining east central Bay of Bengal on October 9. It is very likely to strengthen into a depression over central Bay of Bengal before it is likely to move west-northwest-wards and cross north Andhra Pradesh and adjoining south Odisha in the afternoon or evening on October 11.
Prof Balasubramanian added that the delay in monsoon withdrawal was due to the prevailing La Nina conditions in the Pacific and the strong equatorial dynamics persisting in India which is not allowing the southwest monsoon current or axis to move down south.
The South Asian Climate Outlook Forum, a consortium of meteorologists from south Asian countries, earlier said north Tamil Nadu including Chennai may receive normal rain while Tamil Nadu’s southern coastal districts may receive below normal rainfall this season.
N Puviarasan, director, Area Cyclone Warning Centre, IMD, said an indication of northeast monsoon onset is a persistent flow of northeast winds but now there is a strong flow of northwesterly or westerly winds. “Northeast monsoon will definitely commence after October 25. In 2018 too, we had a delayed monsoon when it commenced in November.”
Y E A Raj, former deputy director general of IMD, said forecast charts show the reversal of winds from westerlies to easterlies may not happen till October 17. “There could be some delay in the onset of NE monsoon. But sometimes easterlies may come on October 17 or 18 and within two days NE monsoon could come with a bang. We will know the condition only after a week…,” he said.