Violent thunderstorms in the Gangetic plains of India are locally known as Kal Baisakhi or Nor'westers. These localised events are generally associated with thunderstorms accompanied by strong squally winds and torrential rainfall.
Severe thunderstorms usually originate in the hills and travel from North to south and then move eastwards. Such storms sustain for longer period of time (8-10 hours) and cover a large area. This was exactly the case with the Bihar thunderstorm.
According to the satellite images available with Skymet, the thunderstorm started building in bordering Nepal region around 5 pm on April 21. By 7 pm, the severe thunderstorm had entered Bihar, covering areas of Purnia, Madhepura, Supaul, Katihar, Madhubani, Darbhanga, Samastipur and Bhagalpur. The storm by this time had covered an area of 30,000 square kilometer.
At around 10 pm the storm had become more severe and reached its peak intensity. The severity of the storm can be gauged from the fact that it covered an area of 2,50000 square kilometer. According to media reports the storm had a wind speed of 65 kmph however, Skymet’s weather sensors in that area picked up a speed of 115 kmph.
The storm sustained in the region till midnight and began to weaken thereafter, moving more eastwards. But by then it had done devastating damage in terms of uprooting trees and electricity poles and ripping apart roof tops. According to media reports the storm has claimed 65 lives so far.
There are observatory platforms in terms of weather radars and satellite imagery in the region which picked up the storm well, sufficiently in advance. However, it is shocking to know that the tragic event passed off without an alert being sounded by the authorities.