Extreme thunderstorms around the global tropics and subtropics

Extreme thunderstorms are studied using the TRMM Precipitation Feature database (Zipser et al. 2006). The database is examined for storms having the lowest microwave brightness temperature, highest radar reflectivity aloft, and / or highest lightning flash rate. In order to establish these as proxies for severe weather, they are compared to reports of large hail in the United States. It is recognized that relationships between remote sensing signatures and surface hailfall will vary regionally, particularly with hail less likely to reach the ground in the warmest climates. Regardless, the satellite-based measurements do provide an objective census of intense thunderstorms around the global tropics, not limited by regional observation networks. Analysis of the passive microwave signatures facilitates future expansion to other satellites that precede or succede TRMM, and that extend beyond the Tropics.

This project focuses on the strongest storms according to the TRMM measures. Most of the storms are found to be clustered in regions including Southeast South America, the Southern United States, Central and West-Central Africa, and South-Central Asia.

A goal of this study is to identify similarities and key differences in the environments that produce these extreme storms. Analysis of the ten-year database and selected case studies will be presented. The very strongest storms observed by TRMM are most often found around Northern Argentina, so our attention is particularly focused on what makes that region stand out from the rest.