A hot air-spewing ‘ridge' (region with high atmospheric pressure) lying spread-eagled over the Bay of Bengal, central and peninsular India and jutting into the Arabian Sea is now triggering a heat wave.
The ridge stretches across west to east right from the west Pacific across South-East Asia, southern India and central Africa until April 9.
It may get ‘click-released' and flung back into position over the Bay by the next day.
But it would have triggered heating of east and central India in phases before the temperature maxima scorches the west and the northwest, says an outlook of the European Centre for Medium-Range Weather Forecasts (ECMWF).
The ‘April heat' should entrench itself over central and adjoining northwest India for the monsoon-enabling ‘heat low' to develop over the region in subsequent stages. In ideal settings, the ‘heat low' (of lower atmospheric pressure) sets up the pressure differential relative to the southwest which the monsoon rides on to bring about maximum possible spatial and temporal coverage.
An India Meteorological Department (IMD) update on Monday said that the highest maximum temperature of 43.1 deg Celsius during the 24 hours ending Monday morning was recorded at Sambalpur in Orissa.
Heat wave conditions have been prevailing Jharkhand, east Madhya Pradesh, interior Orissa, east Uttar Pradesh, Himachal Pradesh, Haryana and northwest Rajasthan. No large change in maximum temperatures is expected over the Indo-Gangetic plains and adjoining parts of central and east India during the next three days.
FLARE-UP SEEN
In fact, the IMD saw a rise in maximum temperatures over Gujarat and adjoining Rajasthan, north Maharashtra and south west Madhya Pradesh during this period. A weather-making north-south trough has been running down from Bihar to North Bay of Bengal bringing isolated thundershowers over east and northeast India, the IMD update said.
Meanwhile, stray moisture transported inland by easterlies from the Bay of Bengal is being dumped as rain over isolated places over the south peninsula – mainly in Tamil Nadu and adjoining Kerala. International models have been suggesting that these rains would get better organised from Tuesday (April 6).
The IMD too has said that isolated rain or thundershowers would occur over extreme south peninsular India during the next two days and increase thereafter.
An IMD experimental outlook for the month of April has indicated enhanced probability of normal to above normal rain for the region, especially interior Tamil Nadu and adjoining Kerala spreading thin to the respective coastal regions.
The Climate Prediction Centre (CPC) of the US National Weather Services seems to suggest that this might happen as easterlies turn southeasterlies over the peninsula and sets up a rendezvous with west to northwesterlies from the Arabian Sea.
This is the most likely scenario unfolding during the week ending April 12 up to which forecasts were available. The opposing wind fronts might go to set up a wind discontinuity/trough breeding thunderstorms. IMD forecasts for the next few days said that isolated rain or thundershowers may occur over Tamil Nadu, Kerala, Lakshadweep, coastal and south interior Karnataka.
Satellite imagery showed convective (rain-bearing) clouds over parts of southeast Arabian Sea, south Bay of Bengal and south Andaman Sea. Low to medium clouds (partially clouded conditions) hung over Jammu and Kashmir, Himachal Pradesh and Uttarkhand due to feeble western disturbance activity.
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