Tuesday, August 04, 2009

Mercury up as weak monsoon extends to more areas

The weak monsoon phase became entrenched in more parts of the country with Gangetic West Bengal alone reporting meaningful rain coverage during the 24 hours ending Monday morning.

The monsoon trough lay parked along an alignment straddling the Himalayan foothills with monsoon westerlies finding their way into the west Pacific, a steaming cauldron away to the east.

PACIFIC CONVECTION

The Noida-based National Centre for Medium Range Weather Forecasting termed it a 'weak monsoon phase' that could last for another four to five days.

In between, a westerly trough is forecast to arrive over east India and even nudge a resident cyclonic circulation over Gangetic West Bengal into some activity.

But it would soon get sucked into the larger trough thrown up by the west Pacific systems, getting weakened in the process. A remnant circulation may potter around the Head Bay before rolling into the Andhra Pradesh coast.

The US Naval Research Lab at Monterey picked at least three areas of convection in the west Pacific, with model predictions favouring two of them to spin up as typhoons.

The feverish convection activity may weaken after August 10 only, according to European Centre for Medium-Range Weather Forecasts.

Some models indicated that the equatorial Indian Ocean may witness enhanced convection after August 10, apparently under the effect of a helpful Madden-Julian Oscillation (MJO) wave transiting to the east.

SOUTHERLY GAINS

The Climate Prediction Centre of the US National Weather Services sees extreme south peninsula getting some rain in the process but leaving the north of the peninsula high and dry.

A trail of moisture would still lead into the west Pacific, where convection and storm-building may start winding down around that time. No major gain is indicated for the Bay of Bengal during this phase according to available forecasts.

The Global Forecasting System model indicated that the westerlies flowing into the west Pacific would maintain their intensity until August 11.

They may weaken a bit after the enhanced convection there lets off some steam, but would still be headed into the west Pacific in the likely absence of a circulation in the Bay, around which they can rally.

MERCURY UP

Meanwhile, India Met Department said that day temperatures have started rising to beyond 40 degree Celsius in northwest Rajasthan, south Haryana and coastal Andhra Pradesh.

On Monday, the monsoon trough passed through Ferozepur, Pantnagar, Raxaul, Sabour and Kolkata before plunging southeastwards into east-central Bay of Bengal.

A prevailing upper air cyclonic circulation has been sustaining overnight rainfall in Gangetic West Bengal. The system is expected to hang around there for a while, according to model forecasts.

Fairly widespread rain with isolated heavy falls is likely over the north-eastern States during the next four days and over West Bengal, Sikkim and Bihar over the next three days.

A warning valid for the next two days spoke about the possibility of isolated heavy rainfall over the North-east, West Bengal, Sikkim, north Bihar, north Orissa and the Andaman and Nicobar Islands.

The following three days (August 6 to 8) would see fairly widespread to widespread rainfall activity over the North-east, adjoining east India and along the foot hills of Himalayas.

Towards the south, rain or thundershowers are likely at a few places over coastal and south interior Karnataka.

Isolated rain or thundershowers are likely over Tamil Nadu, Puducherry, Kerala, Lakshadweep, Andhra Pradesh and north interior Karnataka.

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