Saturday, May 02, 2009

Monsoon Watch-7

Come a W.D. and there was relief from the blistering heat sweeping most parts of the sub continent on Saturday. Relief meaning the temperatures did drop by about 2/3c, and bringing it down from +6c to +3c, but still remaining above normal. Better, after the 50 year April high in Delhi at 43.5c on the 29th.( Palam was over 45c), and another April high in Dehra dun at 41c, and Simla at 28c. Nagpur too set an April record at 47.4c on the 30th. and Khandwa was the highest in the Indian region with 47.5c recorded on same day.
The heat wave has resulted in the forming of the seasonal low over the Rajasthan/sindh region. The surface map shows the low at 1000mb. With the formation of the monsoon low over the landmass of India, the process of the "monsoon build-up" has begun.

In the southern hemisphere, the south-east winds have "almost" established themselves as of today, and are, in about a week, set to take the south-west turn after crossing the equator. This always starts in the Bay sector first. For this, the northward shifting of the ITCZ above the equator is a must. The ITCZ today is at around 5S.

Forecast models estimate a MJO wave from the 10th. of May. An MJO positive wave will surely carry the ICTZ above the equator around the 10th, which is the normal date for it to cross the imaginary line. Even the sea temperatures in the bay are now conducive for this development. (see map).

South-west winds can commence over Kerala from the 7/8th. onwards, and may bring some precipitation alongwith.

The forecast map from NCEP shows the strong rain current (monsoon) approaching the Andaman Islands between the 11th. and 18th. May.

Meanwhile todays W.D. has brought some welcome rain to the northern parts of the sub continent, and the Orissa state, which has been under severe heat. This W.D. will move away in a couple of days.

Monsoon can set in over the Andaman Islands around the 12/13th. of May.

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