Coming into the Arabian Sea as an emdedded "upper air circulation" in an easterly wave, the low pressure system is now, as on 21st., firm over the south east sea off the Kerala coast at 8.6N. The system has been pouring some heavy rain over the Kerala and Karnatak coasts since the night of 20th. Earlier along its path, as an easterly wave, there were unusually heavy to very heavy rains in Tamil Nadu. Kodai.'sMarch has been the wettest ever, with the month's total already at 359 mm, and the previous record of the month was 297 mms. (1947).
This low, if it develops into a depression, it may be the first on record for a very long time in the month of March (no record of any in last 40 yrs. as per my study), in the Arabian Sea.
However, Vinson Kurien, Weather expert from the "Hindu" group, has mentioned and pointed out a very valid and interesting fact. According to his study, since much of the rain is over the Arabian Sea, it may cool down the southern sea waters a bit too much and may hamper the cross equatorial monsoon flow later. As of today, Vinson is correct. The sea temperatures off the Konkan coast is comparitvely hugher than the temperatures off the Karnatak and Kerala coasts and is very distinct in the adjoining image. Also, the sea temperature anomoly this year is far too much on the cooler side, in the central Arabian Sea, as compared to last year.The maps below show this . Also for the record, the anomoly in 2006, the year the monsoon hit Kerala by 26th May, the sea temperature anomoly was more on the +ve side, on the same day that year.
But now, I feel with the formation of a "sudden heat low" of 1002 mb. over central India (south Rajasthan, M.P.), the Arabian Sea "low" may, without intensifying further, by attraction towards the central low, cross the Karnatak coast in a day or two.
I feel, it may be a bit too early to estimate sea temperatures for the monsoon performance yet, and we may still observe the movement of the system across the sea waters to study its thermal effects.