The last few days has seen fairly moderate rains in Andaman Islands. Nancowry has received more than 8 cms rains for the last 2 days. The upcoming few days are expected to see a few places get very heavy rains thanks to the moisture incursion being pushed into the Bay by the Northeast Cold Surge from China.
Northeast Cold Surge which takes its origin in the Siberian Landmass brings a lot of snowfall to places like Hong Kong during this time of the year. As it passes through the South China Sea & Andaman Sea it picks up a lot of moisture bringing in heavy rains in Andaman Islands and parts of Southeast Asia.
Under normal context this is not very similar to the the dynamics of how Northeast Monsoon brings the rains to the Peninsular Coast. But as December gives way to January the High Pressure Zones over the middle East / Central India start to play a role in deciding how these trade winds get moved around over the Indian Sub Continent
As one can observe from the chart the Dry Continental Air partly aided by the regular High Pressure Zones forming over Central India has created an atmospheric dam preventing further propagation of the moist Easterlies onto the East Peninsular Coast. Due to this in the current context the Northeast Cold Surge will dump huge rains over the Andaman Islands while parts of Sri Lanka also could get benefited from this development while Peninsular Coast may not receive heavy rains.
Chennai will continue to see partly cloudy skies with occasional passing showers in one or two places, but mostly the rainfall event is expected to recede after today. Night time temperatures could be warm tomorrow while the temperatures expected to come down as the new week progresses.