Another western disturbance expected to bring thunderstorm to northwest India

May 29, 2023 08:55 AM IST

Strong winds lashed the region early on Saturday with gusts of 110km per hour and disrupted flights and uprooted trees

Another intense western disturbance is expected to bring rain and thunderstorm to northwest India on Monday and Tuesday days after similar weather disrupted normal life in parts of the region. Strong winds lashed the region early on Saturday with gusts of 110km per hour. It was the strongest thunderstorm so far this season and disrupted flights and uprooted trees.

On Saturday, the strongest thunderstorm so far this season hit the region. (HT PHOTO)
On Saturday, the strongest thunderstorm so far this season hit the region. (HT PHOTO)

The India Meteorological Department (IMD) on Sunday issued an orange category asking authorities to prepare for action to prevent thunderstorm-related emergencies across the region until Tuesday.

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IMD senior scientist RK Jenamani said there were similar intense western disturbances in 2020-2021 and they are not entirely unusual. “In some years, western disturbances continue to impact until May.” He added moisture incursion from the Arabian Sea and the Bay of Bengal were also intensifying these systems. “Maximum temperatures have fallen due to prolonged thunderstorm activity. In Delhi, the average maximum temperature is 37°C compared to the normal of 39.7°C.”

Jenamani said the western disturbance between May 23 to 27 was possibly the strongest this year and triggered severe convective weather. “Its impact has been very severe in terms of dust storms and squalls in Rajasthan, Delhi, Uttar Pradesh, and Haryana.”

Jenamani said a dust storm in May 2018 that left over 100 people dead was also caused by the interaction of a western disturbance with easterly winds. “It was the strongest dust storm in the region.”

Thunderstorm activity is expected between March and May but they have been unusually active this season. “We are again expecting a rain and thunderstorm spell for 3-4 days till June 1 or 2 because of an approaching western disturbance, which is expected to induce a cyclonic circulation over north India,” said Skymet Weather vice president (climate and meteorology) Mahesh Palawat.

He added the last western disturbance brought thunderstorms to Delhi and parts of northwest India on Saturday. “Its induced cyclonic circulation was over Punjab and Haryana. Moist winds from the Arabian Sea were also making conditions favourable for intense rain and thunder activity.”

Western disturbances causing prolonged thunderstorm spell, especially towards the end of May, is unusual. “During this time, pre-monsoon rain is caused by instability in the atmosphere following heating of the surface. Western disturbances move to higher latitudes by the April end. Long spells of rain or thundershowers are also rare because the pre-monsoon activity is normally brief and intermittent in north India,” said Palawat.

Former earth sciences ministry secretary M Rajeevan said during monsoon, western disturbances normally do not impact the Indian region, except during monsoon breaks when they can interact with other systems. “Western disturbances move to northern latitudes and a southwesterly wind pattern is established during monsoon season.”

The fresh western disturbance was likely to affect northwest India from Monday. A cyclonic circulation was lying over southwest Rajasthan. A trough was running from this system to northeast Madhya Pradesh. Another trough was also from southeast Madhya Pradesh to south Tamil Nadu in lower tropospheric levels.

Due to these weather features, moderate scattered to fairly widespread rainfall with thunderstorms, lightning, and occasional gusty winds/squall were expected in northwest India until Wednesday. Hailstorm was likely at isolated places in northwest Rajasthan until Tuesday.

No heat wave conditions were likely in any parts of the country until Wednesday even as monsoon has not progressed from Nancowry over the last week. Conditions were favourable for further advance of the monsoon into more parts of south Bay of Bengal, Andaman Sea, and Andaman and Nicobar Islands. Monsoon reaches Andamans by May 22 normally.

In its fresh update on Friday, IMD said rainfall is expected to be below normal, or less than 92% of long period average over (LPA) in northwest India with an error margin of +/-4%. The rainfall is expected to be normal at 94% to 106% of LPA in the rest of the country. The monsoon is expected to arrive in Kerala around June 4 with a model error of +/-4 days.

There has been 14% excess rain during the pre-monsoon season from March 1 to May 27. Northwest India got 25% of excess rain, central India 145%, and South Peninsula 42%. There has been a 31% deficiency of rain in east and northeast India.

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