Damage Potential of Extreme Wind Events—Downburst and Tornado

Abstract

Thunderstorms have always impressed humans and cumulonimbus cloud is one of the most visually striking and photogenic natural phenomena. Unfortunately, the thunderstorms are associated with hazardous weather. Severe thunderstorms are responsible for large amount of wind induced damage around the globe. Unlike large and continental cyclones, severe local storms intensify very rapidly and dissipate after causing damage. Lightning causes many fires around the world each year and leads to severe loss of human life and properties. The worst severe local storm is the tornado, which is characterized by fast rotating column of rising air, which originates on or near the ground where the air swirls and converges at very high speed. Another important event in the thunderstorms is the “Downburst”. Downburst is an anti-tornadic storm characterized by descending air. Downbursts occur when a column of descending air reaches the ground and bursts out violently. This downward air motion causes high wind shear close to the ground unlike a synoptic or atmospheric boundary layer (ABL) wind, where the wind speed is very high much higher above the earth's surface.  It is believed that downburst is generated when the moist buoyant air moving upward can no longer be sustained above and subsides into downdraft. Such storms are popularly referred to as Nor’westers or Kalbaishakhi and Bordoisilla in North-eastern part of India. These storms are due to mesoscale convective systems which develop in the pre-monsoon season (March to May) over the Gangetic West Bengal and North-eastern part of India. In this work, an attempt has been made to simulate both the wind events physically and numerically to estimate the wind profiles and macro flow dynamics for building safer earth fixed structures.

Keywords: ABL, thunderstorm, tornado, downburst, continental cyclone

Cite this Article

Das et al. Damage Potential of Extreme Wind Events—Downburst and Tornado. Journal of Aerospace Engineering and Technology. 2016; 6(2): 28–46p.