Friday, July 09, 2010

Monsoon trough may shift north, weaken

The India Meteorological Department (IMD) has said in its update on Thursday that the monsoon trough would shift northwards close to the foothills of the Himalayas over the next two days.
Rains would now be confined to the foothills, which go to signal yet another weakening trend in the monsoon proving forecasts made by most international agencies.
Some models also fear that a likely revival of Arabian Sea flows around July 18 may have to contend with a brewing cyclone in Northwest Pacific.
Forecasts for the short term indicate the possibility of rain-stopping northwesterly flows returning in full force to northwest India – and along with them, the hot climes across the border from Pakistan and West Asia.
Monsoonal flows over the Arabian Sea have already started weakening, according to the European Centre for Medium-Range Weather Forecasts (ECMWF) on Thursday.
The IMD weather charts showed rain-bearing monsoon southwesterlies confined to just along the Konkan-Goa coast on Thursday.
Towards the south, these flows were northwesterlies going around a high-pressure cell over southwest Arabian Sea.
Going forward into the next week, the IMD charts showed a barrage of westerly to northwesterly flows establishing their presence across the landmass.
According to the ECMWF, it would take another 10 days for the southwesterly flows to rebuild in strength over the Arabian Sea.

But a ‘break-monsoon' situation, or mid-season drought conditions, may likely be averted since parts of the west coast are shown to continue to receive varying amounts of rainfall, as per forecasts by US National Centres for Environmental Prediction (NCEP). This is despite some tell-tale features – a westerly trough making a presence and an anti-cyclone from the Arabian deserts poking its nose into central India – establishing themselves, albeit briefly, during the period.
As is the usual case when the monsoon goes into a lull after having covered the whole country, rains would now be confined to the area around the Himalayan foothills.
The IMD has said that scattered rain/thundershowers would occur over Uttar Pradesh and Bihar during next 24 hours, before increasing thereafter.
These regions have not seen any significant rain despite the monsoon being declared as having covered the whole country 10 days ahead of normal.

Extended forecast until July 13 (Tuesday next), said that widespread rainfall with isolated heavy to very heavy falls would occur over Uttar Pradesh, Bihar, sub-Himalayan West Bengal, Sikkim and the Northeastern States.
Meanwhile, the expected revival of Arabian Sea flows around July 18 may also coincide with the formation of a tropical cyclone in the Northwest Pacific, the ECMWF said.
This possibility has been highlighted by the Climate Prediction Centre of the US National Weather Services as well.
Were this to pan put out in reality, a part of the reviving monsoon flows cold could be spirited away by the brewing cyclone.
ECMWF has indicated this possibility wherein some flows are shown to steer themselves around the peninsular tip to be directed into the Bay of Bengal and onward into the South China Sea.
The IMD said in its update on Thursday that the offshore trough from Gujarat coast to Kerala coast persisted.
Forecast until Sunday said that fairly widespread rain or thundershowers would occur over the Northeastern States, sub-Himalayan West Bengal, Sikkim, Gujarat State, Maharashtra, Madhya Pradesh, Lakshadweep, coastal Karnataka and Kerala.
Isolated rain or thundershowers are likely over Punjab, Haryana, Chandigarh, Delhi, Himachal Pradesh, Uttarakhand while being scattered over Chhattisgarh, Orissa, Andhra Pradesh and Tamil Nadu.
That the rains may extend to the east and southeast coast is another pointer to the fact that the monsoon would be in a weak phase.

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