Wednesday, September 24, 2008

In the last blog, I mentioned that the monsoon was receding, but we had to observe the bay low which was forecasted for this week, before the rainy season restarts its reversing.

Now, there is big drying up of the Subcontinent, a sign of the reversal of the SW Monsoon as it withdraws.

A feeble low has formed in the North Bay of Bengal once again. It might just precipitate fairly widespread rainfall West Bengal, Sikkim and coastal Orissa only, and not take the path of the last depression.. It clearly lacks intensity to drive any further than that. Thus, as seen in the IMD streamline, the seasonal anti-cyclone (high pressure area with dry weather) is advancing in from extreme west Rajasthan.

Now, what about next week? No forecasts have been made about any fresh low in the bay now, but we have to watch the typhoon Hagupit, a Category-3 storm raging currently in the Northwest Pacific and heading towards the south-east China coast. Also, next in line, perhaps, will be a tropical wave centered in the area of Yap Islands as of Tuesday. This wave could become the next tropical depression as its drifts west-northwest over the southern Philippine Sea.

But all this activity in the Pacific, may be a booster to the North-East monsoon setting. Later in about 100/12 days hence, the leftovers of Hagupit could reform as a well-marked monsoon low near the head of the Bay.

This should initiate the onset of the North-East monsoon around mid-October. But before this, the southwest monsoon should have withdrawn completely , and the winds should change, which is indicative in today's map above. September 30 is the normal date for this to happen, but, due to the initial hiccup in its widhrawal, is behind schedule at least as of now.

It had been forecasted by some models and forecasters in the last week, of a MJO reviving, and likely increase of rain in the southern peneinsula. Now, as of this week, MJO forecasters see a depleting MJO causing a dry spell in the southern region of India. However, I feel, at this time of the year, specially during the "changing season" period, the effects of an MJO over the sub continent is minimal, due to stronger seasonal changes.

Almost dry weather in all of the sub continent (barring Bengal, Sikkim and some isolated rain in the north-east), till next week. However, "local" thunderstorms , though scattered, can be expected in Maharashtra, during the next 5/6 days. That is during the receding of the monsoon.






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