Study on Generation of Tornado-like Flow Field and Visualization by Funnel Clouds

Effect of Tornado Characteristics on the Shape of Funnel Clouds

Abstract

Currently, Fujita scale is usually used to estimate the wind speed of tornadoes from damages by them. However, this method becomes invalid when there is no damage. Therefore, other method to estimate characteristics of tornadoes independent of damages is required. In this study, the relations between characteristics of tornadoes and shapes of funnel clouds were investigated by using computational fluid dynamics technique to make a new method to estimate characteristics of tornadoes with photographs and movies of funnel clouds. As results of this study, it was clarified that humidity and maximum wind speed controlled the diameter and the height of funnel clouds respectively.