Tuesday, April 13, 2010

Thunderstorms erupt in N-E as heat builds to west

Thunderstorms have erupted once again over the North-East bringing rain to many places over Arunachal Pradesh, Assam and Meghalaya during the past 24 hours ending Monday morning.

These seasonal showers triggered by north-westerly winds (Nor'westers) have steadfastly refused to venture out further to the southeast, especially over West Bengal.

RAISED CHANCES

This has led mercury to gallop to the highest in at least last 10 years' recorded history. Coverage of clouds as revealed by satellite pictures on Monday does not indicate anything to the contrary either.

According to the US National Centres for Environmental Prediction, the convective available potential energy (CAPE) values are high for areas in and around the Sunderbans and Metro Kolkata.

High CAPE values signal the probability for thundershowers, which have largely evaded this region so far. Towards the south, these values continue to be high for Kerala and adjoining south-interior and coastal Tamil Nadu.

In fact, Kerala is among the few meteorological subdivisions that have recorded normal rain during the period from March 1 to April 7, an update from India Meteorological Department (IMD) said on Monday. The others are Konkan, Goa, Assam and Meghalaya (excess); and Marathwada, Vidarbha, Arunachal Pradesh and Nagaland-Manipur-Mizoram-Tripura (normal).

HEAT WAVE

A crippling heat wave has held centre-stage over large parts of east and northwest India during the 24 hours ending Monday morning.

Parts of east-central India – Jharkhand, interior Orissa, Vidarbha and Telangana – managed to escape the blast of oppressive heat generated by the trans-Pacific ridge (high-pressure region that prevents cloud-building from taking place). This was due to proximity of these regions to a trough from Bihar running down south-southwest to north coastal Karnataka.

Meanwhile, Sambalpur in Orissa recorded the highest maximum temperature of 45.6 deg Celsius overnight on Monday. Widespread heat wave to severe heat wave conditions prevailed over many parts of Punjab, Haryana, Delhi, north Rajasthan and parts of Himachal Pradesh. Heat wave conditions also prevailed over many parts of Uttar Pradesh, Jharkhand, interior Orissa and parts of Chhattisgarh, north Madhya Pradesh, Bihar and Vidarbha.

WESTERN DISTURBANCE

The IMD traced a western disturbance lying over north Pakistan and adjoining Jammu and Kashmir. It is forecast to affect the western Himalayan region during the next 24 hours.


The system that features a core of winds cooler than the prevailing air in the northwest but packing moisture content is expected to trigger widespread rain or thundershowers over Jammu and Kashmir during the next 24 hours.

The IMD expects the thunderstorms to roll down the hills of the northwest onto the plains as well, with scattered rain or thundershowers being forecast for Himachal Pradesh, Uttarkhand, Punjab and Haryana during the same period. Satellite cloud imagery showed the presence of low to medium clouds (partly clouded conditions) over Jammu and Kashmir, parts of Himachal Pradesh, Uttarkhand and Punjab.

The cloud formation is expected to help bring down the maximum day temperatures briefly over these regions.

Westerlies from an earlier western disturbance passing into the east are already causing thundershowers over the northeast. This activity would get another fillip as the incoming system too moves, as it will, to the east and northeast.

Scattered to fairly widespread rain or thundershowers have been forecast to occur over Arunachal Pradesh, Assam, Meghalaya and isolated over Nagaland, Manipur, Mizoram and Tripura until Thursday.

Isolated rain or thundershowers would also occur over Karnataka, Kerala and Lakshadweep during this period, the IMD said.

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