Thursday, August 20, 2009

Arabian Sea warms up ahead of reviving monsoon

India Met Department (IMD) has forecast the possibility of isolated heavy rainfall over west coast during the next two days ahead of an organised revival of monsoon over the west coast.

An upper air cyclonic circulation was seen hovering above Lakshadweep islands and adjoining southeast Arabian Sea. South Konkan, Goa, Kerala, coastal Karnataka and Lakshadweep are bracing to witness a spurt in rains.

MJO ASSISTANCE

The Climate Prediction Centre (CPC) of the US National Weather Services sees increased chances of above normal rainfall for the equatorial central Indian Ocean (around Sri Lanka) and southern India during August 18-24.

This is being attributed to the passage of an eastward-bound and periodical Madden Julian Oscillation (MJO) wave featuring enhanced convection in the upper levels of the atmosphere.

The lower levels too are expected to resonate in kind, setting up the required conditions on ground to sustain a rainfall regime that will move north along the coast before spreading east over central India.

The active monsoon phase may last until the month-end, the CPC said. The Wheeler model tracking MJO movement ventured to suggest that the monsoon would be active up to September 6.

But two others - the Jones model and the Empirical Wave Propagation technique employed by the CPC - saw the proceedings wearing off by the month-end. A suppressed convective phase (dry weather) of the MJO will have moved in over equatorial Indian Ocean by then.

HEAVY RAINS

The International Research Institute (IRI) for Climate and Society at Columbia University saw wetter than normal conditions over madhya Maharashtra and south interior Karnataka during August 19-24.

Towards the north, it saw a belt of unusually heavy rains moving west from Bihar and sub-Himalayan West Bengal towards the northern part of central India and even up to west Rajasthan.

In fact, the Noida-based National Centre for Medium Range Weather Forecasting sees an upper air cyclonic circulation shaping up over east Uttar Pradesh by August 22 (Saturday), which will stay active until Tuesday next.

This will bring rains over Uttar Pradesh, and according to the IRI forecasts, could move west taking the rains along.

An IMD update said that monsoon has been active in Assam, Meghalaya, sub-Himalayan West Bengal, Sikkim, east Uttar Pradesh and Punjab during the 24 hours ending Wednesday morning.

The causative upper air cyclonic circulation over northwest Uttar Pradesh and adjoining Uttarakhand has not shown any sign of weakening.

It will continue to bring fairly widespread rainfall over north Uttar Pradesh and Uttarakhand during the next two days with isolated heavy fall during next 24 hours.

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