Saturday, May 26, 2007

Monsoon Watch - 18

As indicated in "MW"-17, the W.D. is today moving across Northern India and Pakistan. Rain has been reported from many places today in North India, and the temperatures were below normal all over the North (India and Pakistan). Now, this is in sharp contrast to the heat that was prevailing in late April and upto mid May. Different forecasts have been seen on the future behavior of this W.D.

IMD expects this W.D. to move away in two days, while some models expect the W.D. to hang around the region for a week more, that is till 2/3 June.
So long as this is in place, the SW Monsoon can not proceed northwards. Personally, looking at the situation, "push effect" from the Southern Hemisphere cross winds is likely to move the W.D. away in two days, and get the monsoon current back on stream from 28th.May. The anti clock-wise wind movement is flattening (luckily),and the streamline shows some re-grouping. The south West winds should pick up from early next week, and bring in the cloud formation of the monsoon again in the Arabian Sea and a low pressure to form off the west coast of India around 1 June. Hence, I expect the monsoon to be in Kerala by the 1/2 June.
The sea temperature of the Arabian Sea is also at 31, which is ok to form convective clouds, when the cross winds bring in the moisture.

A small strip of sea temperature off the Somali coast should be low, at 18-20 degrees about 10 days before the monsoon clouds arrive on the West coast of India. The stronger the temperature gradiant between the strip and the vast area of the Arabian Sea, stronger the impact on the monsoonal winds, forcing them towards the east. Today, the strip off the Somali coast is at around 25 degrees, and cooling every day.

Also, if the prevailing W.D. moves away in a day, the northern regions and areas of Sindh and central India can expect a sudden revival of the heat. This will help in the quick formation of the seasonal monsoon low in a week or so.

But the rain I mentioned in the last blog, coming up the west coast of India this weekend is not to be mistaken for the monsoon. These rains are due to the upper westerly trough of the W.D. and will move eastwards. The interior areas of Karnataka and TamilNadu are bound to get rains this week end as a result of this westerly trough moving eastwards. But these rains will dry up, as the real monsoon current closes in from behind, and this monsoon current will travel north.



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