Wednesday, November 25, 2009

Active monsoon conditions over south TN, Kerala

North-East monsoon has been active over south Tamil Nadu and Kerala during the last 24 hours ending Monday morning, according to an update from the Chennai Met Centre.

Rainfall occurred at most places over south Tamil Nadu and at many places over north Tamil Nadu and Kerala and at a few places over Lakshadweep, coastal Andhra Pradesh, coastal and south interior Karnataka.

Forecast for the next two days spoke about the possibility of rain or thundershowers mainly over south Tamil Nadu and south Kerala.

A few places over north Tamil Nadu, Puducherry, north Kerala, Lakshadweep, Rayalaseema, coastal Andhra Pradesh, coast and south interior Karnataka also are expected to witness thundershowers.


Sea-surface temperature (SST) maps on Monday revealed that the stretch of hyper-active convection linking southeast Bay and adjoining East Indian Ocean to southwest Bay of Bengal around Sri Lanka has let off some steam due to incessant rains over the past few days. These seas are still warm beyond the threshold limit allowing them to host, or facilitate easy passage to, weather systems that choose to move towards Sri Lanka or mainland India.

This narrow stretch of comparatively cooler waters is bordered on both sides by the warmest waters (entire Bay of Bengal to the north and East Indian Ocean to the south) of the northeast monsoon region.

According to international model forecasts, the Bay of Bengal would increasingly get busier with easterly convective rain bands shown to extend into its northern flanks during the course of the week. The European Centre for Medium-Range Weather Forecasts (ECMWF) projected that the build-up may culminate in the formation of a low-pressure area just off central and south-central Tamil Nadu coast during early December.

This is likely to coincide with the landfall of another powerful typhoon over the Philippines, the ECMWF predictions said.

The US National Centres of Environmental Prediction (NCEP) is of the view that entire southern peninsula would continue to witness scattered to fairly widespread rains during this week.


This outlook also suggested that north Bay of Bengal would witness raised level of activity, which is in line with the ECMWF outlook. NCEP’s forecast for the first week of December indicated fresh convection starting to build over equatorial Indian Ocean.

An India Meteorological Department (IMD) update on Monday said that the cyclonic circulation over south west Bay of Bengal and adjoining Comorin area had shifted to over southeast Arabian Sea

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