The temperature regime over northwest India until April 4 is like to have ‘significant favourable impact' on the standing crop and its harvest in the core wheat belt in northwest India.
This is being facilitated by a train of incoming weather-setting western disturbances from across the northwest border, according to Dr Akhilesh Gupta, leading operational forecaster and Adviser with the Department of Science Technology.
CAPPING MERCURY
Speaking to Business Line, he said the emerging weather pattern would be set into motion by a westerly system entering the region on Thursday. This would help cap the mercury level and bring it down from the current high of 38.5 deg Celsius over the wheat belt in Rajasthan, Punjab, Haryana and west Uttar Pradesh for three days until Sunday.
The eastward movement of the system over central and east India may not elicit a prompt response initially but the temperature maximum may come down by a degree of one or two deg Celsius subsequently.
The mercury would once again pick up over northwest India on Monday and Tuesday (March 29 and 30) ahead of the arrival of a follow-up next western disturbance, but only to fall from March 31 to April 4 as the cooling phase unfolds.
NO THUNDERSHOWERS
In this manner, any sustained heating of the core wheat belt, which is prejudicial to crop prospects, is ruled out during the early harvest phase as well. What is more, weather parameters also seem to negate the possibility of seasonal pre-monsoon showers interfering with harvest operations for at least the next seven to 10 days, Dr Gupta said.
This is the time for pre-monsoon convective activity to begin, which has both positive and negative implications for the temperature regime and agriculture prospects. Normally, the seasonal thunderstorms (called Nor'westers or Kal Baisakhi variously in local parlance) break out first over the northeast and propagate in phases to east India, central India and north India. According to Dr Gupta, the northeast would receive the first major thunderstorm with fairly widespread showers on Sunday (March 28).
Dynamical calculations based on convective available potential energy (Cape) values, which indicate ‘conditional atmospheric instability,' are shown to jump thrice as much during a three-day-period ending Tuesday (March 30).
This is indicative of the atmospheric buoyancy and vertical motion of air that sets up clouds. The Cape values are shown trebling from 1,000 joules/kg to 3,000 joules/kg on Tuesday, Dr Gupta said.
Towards the south, an easterly wave is likely to impact the southern peninsula for three days from March 28 to 30. This is expected to trigger thundershowers and rains over southern Tamil Nadu and adjoining Kerala.
Meanwhile, an India Meteorological Department (IMD) update said on Tuesday that maximum temperatures have fallen by 2-3 deg Celsius over most parts of Gujarat and some parts of Rajasthan during past 24 hours leading to abatement of heat wave conditions.
But severe heat wave to heat wave conditions prevailed over some other parts of Rajasthan and southwest Uttar Pradesh. Heat wave conditions also prevailed over many parts of Madhya Pradesh, Chhattisgarh, Jharkhand, and over parts of southeast Uttar Pradesh, Orissa and isolated pockets of Telangana.
The ‘top heat' has shifted eastward from Gujarat to Wardha and Chanderpur in Maharashtra which recorded the day's maximum of 43.0 deg Celsius on Monday. Scattered thundershower activity has already occurred over the Northeastern States, sub-Himalayan west Bengal and Sikkim.
This could be attributed to the trough thrown open by the movement of a prevailing western disturbance on its way out to the east and out of the country. The north-south trough extended from Sub-Himalayan West Bengal to North Bay of Bengal and featured moisture incursion from the Bay of Bengal.
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