Seasonal thunderstorms have announced their arrival with a vengeance over Bihar and West Bengal with typically destructive gale-force winds wreaking havoc in the contiguous border areas of the States late on Tuesday night.
Brute force
Thunderstorms during this time of the year are seasonal in nature and are called Nor'westers, thanks to the trigger in the westerlies blowing from northwest India.
Nor'westers can at times pack a deadly punch with accompanying high winds, lightning and thunder activity. Moisture incursion over heated land sets up the ideal conditions for the storms to take shape.
India Meteorological Department (IMD) said in its update on Wednesday that the causative land-based trough ran down from Bihar to south Chhattisgarh across Jharkhand and Orissa.
WESTERLIES TO GAIN
Another trough ran down from north Karnataka to Tamil Nadu with an embedded cyclonic circulation over Karnataka and neighbourhood.
Satellite cloud imagery showed the presence of low to medium clouds (partly clouded conditions) over parts of peninsular India, the north-eastern States, south-east Arabian Sea and south Bay of Bengal.
Meanwhile, international weather models indicate that the westerlies would hold sway over the region during this week and possibly the next, with western disturbance activity picking up once again.
The first of the series may enter the northwest as early as Thursday (tomorrow) and may get particularly accentuated over east and northeast India due to the presence of the trough. The wind strength and the depth of the trough are mutually complimentary, with one feeding the other. Since the Nor'westers have drawn first blood in the Bihar/West Bengal region, it is likely that the latter could witness continued activity over the next few days as well.
The IMD has forecast scattered to fairly widespread rain or thundershowers over the north-eastern States during the next 24 hours but may decrease thereafter.
Isolated rain or thundershower is likely over West Bengal, Sikkim, Jharkhand and Orissa during the same period.
Widespread showers
Forecast until Monday hinted at the possibility of scattered to fairly widespread rain or thundershowers with isolated thunder squall over the Northeastern States. According to the US National Centres for Environmental Prediction, the week ending April 21 would see isolated rains over parts of northwest India, scattered over northeast India and the southwest coast (mainly Kerala, south-coastal Karnataka).
But the proceedings would likely get a leg-up during the week that follows (April 22-30) with showers activity being indicated from southwest Rajasthan to the rest of the northwest India, east India and northeast India.
The northeast is shown to ‘light up' yet again thanks to raised level of thunderstorm activity from Nor'westers.
The ‘rain trail' from the northeast will sneak down south-southeast to east India, east-central India and adjoining peninsular India before linking up with the weather activity along the southwest coast.
This is being mainly attributed to the arrival of strong western disturbance around April 20, which is expected to dig its heels into northwest India before moving further east.
Given this context, the heat wave in the northwest and east India might scale down during the last 10 days of the month. But this could also interfere with the heating process necessary to set the stage in the northwest for monsoon to drive in.
Meanwhile, overnight on Wednesday, heat wave conditions prevailed over many parts of Northwest India, north Gujarat, Chhattisgarh, interior Orissa, Jharkhand and isolated pockets of northeast Madhya Pradesh, Vidarbha, costal Andhra Pradesh and costal Orissa.
The highest maximum temperature of 45.5 deg Celsius was recorded at Hirakud in Orissa. Rain or thundershowers have occurred at many places over the Northeastern States and at a few places over Karnataka and at isolated places over Kerala during the past 24 hours.
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