Nor’wester or Kalbaishakhi is a very special severe thunderstorm phenomenon during premonsoon season over North-East India. In this event, cumulonimbus (Cb) cloud cells are arranged in a special characteristic manner of squall-lines and the whole system moves with varying speed from North-West to South-East. The breadth of such a line is one tenth of its length, and the heights in different segments can vary from 7 to 18 kilometers. This system is associated with squally winds of the order of 45 kilometers per hour or more, high intensity of rainfall, huge thunder, lightning and hails. Reduction of atmospheric temperature yields relief to the people from severe heat wave conditions of summer. The downdrafts from such combination of cells yield high magnitudes of squalls causing destructions of various dimensions, like uprooting of trees, electric polls, electro-cuttings, damages of weak structures and crops, blockage of roads and railway traffic. Several flights are cancelled over the area of the squallthunderstorm. The effects of Nor’wester have tremendous impacts just after the occurrence of the event. Government has to provide adequate fund depending on the frequencies, dimensions of the occurrences of the event. Equipments and efficient manpower are to be kept ready to serve effectively in the affected areas. Enough shelter zones with sufficient food, drinking water, medicine and doctors are to be provided for the victimized people. The remedial measures must be taken when meteorological departments issue the forecast of these events. The aircrafts, packed in the airfields must be shifted to the safety zone on receipt of the weather warning. The paper highlights the characteristics of such a severe weather event causing natural disaster, and the necessary safety measure for the people.
|Keywords:||Nor’wester, Squall, Cumulonimbus Cloud, Natural Disaster|
Teacher Fellow, Institute of Radiophysics and Electronics, Calcutta University, Kolkata, West Bengal, India