Northeast monsoon has generally remained dormant during 2nd half of November for Chennai. Otherwise, November happens to be the rainiest month for the capital city of Tamil Nadu. Courtesy, active monsoon conditions during the 1st half of month, both the observatories, Nungambakkam and Meenambakkam, have crossed their monthly normal rainfall. Paucity of easterly waves and absence of any low pressure or depression, during the last 2 weeks have resulted submissive weather conditions without any significant rainfall. Between, 16th and 29th November, Nungambakkam has recorded only 11.4mm rainfall and the airport observatory at Meenambakkam, a mere 2.7mm.
Today and tomorrow, mostly partly cloudy sky with high humidity and sultry conditions will prevail. A change in these conditions is likely, very soon. Strengthening of easterly stream along the coastline will trigger the northeast monsoon activity, commencing 01st December, when light rain and showers are expected. Intensity and spread of monsoon showers is likely to pick up and become moderate between 02nd and 04th Dec. City and suburbs will possibly see a dip in the subsequent 48hr, on 05th and 06th December and a spike again, thereafter.
A cyclonic circulation is likely to emerge over South Andaman Sea and adjoining Bay of Bengal (BoB ) on 03rd/04th December. This weather system will be an off-shoot of low pressure area over Gulf of Thailand, making its way as weak circulation, over the Indian Seas. This circulation is expected to become more marked and may turn into a low pressure area, over the South-Central Bay of Bengal. Easterly stream over the BoB is likely to steer this weather system over Southwest BoB, off Tamil Nadu coast on 06th Dec. Proximity of the low pressure first and breaching the coastline later, will trigger heavy rains along and off the coast, including the capital cities of Chennai and Puducherry , between 06th and 08th December.