Kalbaishakhi or Nor'westers are severe thunderstorms with lightning, hail, and strong winds striking eastern parts of India during the Pre-Monsoon season. Thunderclouds could be embedded with tornadoes, roaring, and swirling moving with tremendous speed to entail destruction all along its swathe. One actually needs to observe to believe its ferocity. Bihar, Jharkhand, and West Bengal are very sensitive to these storms which are notorious for inflicting damage to the men and material.
The entire region has already gone through a hectic round for many days and everything is not yet over and done. Mainly heat of the land and moist winds of Bay of Bengal work in tandem to build towering clouds that keep moving and regenerating to extend these conditions over a large area. Courtesy prolonged weather activity, the entire region has recorded a huge surplus for the season so far:
Pre-Monsoon activity has been interspersed with short breathers and looks like building up again to commence right from the early days of May and endure for a week shifting pockets of intense activity within the states. The cyclonic circulation over Bihar and neighborhood is fueled by the moisture from the Bay of Bengal. Rain and thundershowers will commence from 01st May, gather pace and intensity, and continue till 08th May.