Study of pre-storm environment by using rawinsonde and satellite observations

Abstract

Four groups of severe storms with a total outbreak of 27 tornadoes have been studied by using satellite remote sensing and rawinsonde observations. Geographical distributions of the areas of high moisture concentration at 850 mb height, 7 to 12 hours prior to the formation of the storms, using the best available conventional rawinsonde soundings, and 2 to 3 hours prior to the touchdown of tornadoes, using the three hourly AVE-SESAME soundings, were analysed in conjunction with the ambient pre-storm wind and air mass stability. Using the area of high moisture concentration as a basis, the time-dependent geographical variation of the tropopause height distribution was analysed. It was found that, within the area of a low-level high concentration of moisture, the local tropopause height was lowest at the time of the storm cloud formation and development. The potential energy storage per unit area for the overshooting clouds penetrating above the tropopause is closely related to the intensity of the storms produced, in terms of the Fujita scale of storm damage. To make up the discrepancy of more than 3-hour intervals of available sounding data, numerical cloud modelling is carried out. The results obtained from the cloud modelling are in agreement with the results of satellite remote sensing and rawinsonde observations drawn earlier.