India Meteorological Department (IMD) has ruled out the possibility of a heat wave at any part of the country during next five days as weather-friendly cyclonic circulations and troughs aligned suitably across vulnerable regions over North-West India, Central India, and East & North-East India, in tandem with evolving pre-monsoon season.
To the north-west, a western disturbance as a trough crossed in from East Pakistan into west Gujarat and south-west Rajasthan. An upper air cyclonic circulation hung over south-west Rajasthan. They will combine to trigger isolated light to moderate rainfall, thunderstorms, lightning and gusty winds over Uttarakhand, Punjab, Haryana Chandigarh, Rajasthan and Uttar Pradesh.
Troughs, low pressure
Troughs are elongated areas of low pressure, and are receptacles for moisture whipped up by cyclonic circulations. Warm air and low pressure allow moisture to be hoisted higher into atmosphere where it cools to precipitate as rain or thunderstorms.
Channels carved into atmosphere by temperature, pressure and wind patterns, these troughs are pre-monsoon formations. They criss-cross land at random and shift base constantly, presiding over violent weather marked by heavy rain, thunderstorms, lightning and hailstorms. To the East and North-East of the country, typically destructive weather assumes moniker Kal Baisakhi.
Pre-monsoon systems
Pre-monsoon troughs die out with onset of monsoon. On Thursday, a trough ran down from cyclonic circulation over south-west Madhya Pradesh to north interior Karnataka. Winds blowing ashore from an anticyclone over Bay of Bengal emptied moisture into it. This will set off isolated to scattered light to moderate rainfall, thunderstorms, lightning and gusty winds over Tamil Nadu, Puducherry, Karaikal, coastal Karnataka, north interior Karnataka, coastal Andhra Pradesh, Yanam and Rayalaseema.
Telangana hailstorms
A similar pattern may unfold over Kerala, Mahe, south interior Karnataka and Telangana for next five days. Isolated hailstorms are likely over Telangana for two days. Isolated to scattered light to moderate rainfall, thunderstorms, lightning and gusty winds are likely over west Madhya Pradesh, eEast Madhya Pradesh, Vidarbha, and Chhattisgarh into the weekend.
Flare-up in east
Scattered to fairly widespread light to moderate rainfall, thunderstorms, lightning and gusty winds (50-60 km/hr ) are likely over plains of West Bengal, Jharkhand and Odisha for four days. Isolated to scattered light to moderate rainfall, thunderstorms, lightning and gusty winds are likely over hills of West Bengal and Sikkim. Isolated hailstorms are also likely over east Madhya Pradesh, Vidarbha, Chhattisgarh, Jharkhand, Odisha, Bihar, and hills and plains of West Bengal and Sikkim.
Isolated heavy rain
A cyclonic circulation lies over north-east Assam which will trigger scattered to fairly widespread light to moderate rainfall/snowfall, thunderstorms and lightning over Arunachal Pradesh with isolated heavy rainfall/snowfall. Scattered to fairly widespread light to moderate rainfall, thunderstorms, lightning and gusty winds are likely over Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura during next five days. Isolated hailstorms are also likely over south Assam for two days.
