Friday, June 01, 2007

Monsoon Watch - 21

Is the situation favourable for the further advance of the monsoon into Goa and Maharashtra, or is it not ? This is the very complicated question that every forecast model is facing, and as Jim from Accuweather aptly puts it -" Given that rainfall is often poorly handled by numerical forecast models," unquote, it is one of the most complex situation in recent times.

The monsoon has advanced upto Karnatak coast in the west, and upto the Andaman Islands in the Bay. Now in the west, today ,a depression has formed, which has all the possibilities of strenghtning and going upto the cyclone stage. Good enough to pull the monsoon up the west coast. But due to a ridge axis on the sub continent, the system is forecasted to move North west, away from the west coast and towards Southern Oman. That means, energy will be absorbed towards the system, and the winds will twirl around the cyclone, leaving little for the monsoon to advance up the west coast.In this eventuallity,further movement of the monsoon can be delayed,by 4/5 days, till the clouds regroup again. As a result, even the IMD has delayed the further advanve of the monsoon by at least another 3 days.

But the above mentioned ridge, or high aloft is necassary to attract the monsoon upwards after the passing of the Arabian Sea system.This ridge is exactly the opposite of a W.D. In fact, due to this, the temperatures in the North have started heating, with 4 places at 46c in Pakistan today and 2 places with 45c in India today. So it is better the system moves away from the west coast.

As ,if this Arabian Sea system, does not move North West, then its moving north will surely bring rain to the west coast, but will only mean that the much required mentioned above ridge is not effective. And further it will only be a passing phase of rain, as then a W.D. will prevail, and absorb the system, and bring delays in the monsoon by upto a week.

The Bay segment seems to be still dormant. No further advance is seen in the next few days, and development of a system in the Bay has to wait till a "pulse" imerges from the far east, or from the Bay itself.After the cyclone "Akash", the Bay waters did cool down a lot, and heating again is required to start some activity.

But ,overall, the assessment has been quite on target. Since the MW-1 on 1st. April, through April, it has been maintained that the monsoon should hit Kerala in the "last week of May''
or "ahead of schedule". Throughout May, the sea tempertaures and heat waves and pressures were observed, and the targets for the monsoon date was being mentioned in the MW's, and Mumbai's pre monsoon shower was indicated way ahead on 8th. May. As I always write, we have to only observe,we cannot control. One can observe and put in views, but one can never actually control the actual weather event.

In the next few MW's I shall also try to analyse the quantum of rain expected during the rainy season. Please give your views and comments on this at

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