Tuesday, December 01, 2009

Scattered rains forecast for southern peninsula

Isolated rainfall continued to be reported from Tamil Nadu during the 24 hours ending Monday morning, especially along the southeastern coast of the State.

This happened as the previous day's cyclonic circulation over adjoining southwest Bay of Bengal descended to lower levels and moved west towards Sri Lanka to set off weather in the neighbourhood.

Satellite cloud imagery on Monday morning showed convective clouds over parts of southwest Bay of Bengal while low to medium clouds were present over parts of Tamil Nadu.

ISOLATED RAIN

An India Meteorological Department (IMD) outlook said that isolated to scattered rainfall activity is likely over extreme south peninsular India during the next three days.

According to the Regional Met Centre, Chennai, isolated rain or thundershowers are likely over Tamil Nadu, Puducherry, Kerala and Lakshadweep during the next two days.

Meanwhile, international models continued to suggest gradually increasing rain cover over more parts of the southern peninsula during the first and second weeks of December.

The European Centre for Medium-Range Weather Forecasts (ECMWF) saw a weather-generating system being triggered off the northwestern-most tip of Indonesia from Thursday.

The trough of low pressure thus created would slowly propagate itself in west-northwest direction, growing in size and coverage during the first week of December. The system is predicted to reach southwest Bay of Bengal off Tamil Nadu and Sri Lanka around December 8.

Here, it is expected to intensify, before impacting the southeast coast of Tamil Nadu and northwestern Sri Lanka to the immediate south, the ECMWF said.

IN AGREEMENT

The precipitation forecast model of the US National Centres for Environmental Prediction (NCEP) is more or less in agreement with this outlook. It indicates rains off and along the Tamil Nadu coast and distributed thin but fairly widespread over the larger southern peninsula during November 30 to December 7.

The week that follows (December 8 to 16) would witness a burst of rains over southeast and adjoining central Tamil Nadu. Some of the rains would get radiated to the northern coast as well.

Significantly, the ECMWF doesn't show any significant movement of western disturbances during the first week of December and early into the second as well.

Given this, it is likely that minimum temperatures would tend to look down over northwest and central India likely setting of cold wave conditions over some parts.

Meanwhile, on Monday, maximum temperatures stayed above normal by 2 to 3 degrees Celsius over parts of Kerala, south costal Andhra Pradesh, Gujarat and the Northeastern States indicating near absence of cloud cover over the regions.


MERCURY PATTERN

But they were below normal over Punjab, Haryana, Uttar Pradesh and parts of east Madhya Pradesh as a western disturbance impacted the western Himalayan region. Isolated to scattered rainfall or snowfall has been forecast over the region during the next two days.

Night temperatures were below normal over Maharashtra, north interior Karnataka, north Andhra Pradesh, south Chhattisgarh, Orissa, east Uttar Pradesh, north Chhattisgarh, Punjab, Jharkhand, parts of Bihar and Gangetic West Bengal.

The lowest minimum temperature of 4 degree Celsius was recorded at Amritsar. The IMD did not see any significant change in minimum temperatures during the next 24 hours over northwest India but a slight fall thereafter.

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