Using satellite data to identify and track intense thunderstorms in South and southern Africa

Estelle De Coning,Louis Van Hemert,Morne Gijben,Bathobile Maseko

doi:10.17159/sajs.2015/20140402

Abstract

To issue warnings of thunderstorms, which have the potential for severe weather elements such as heavy rainfall and hail, is a task of all weather services. In data sparse regions, where there is no or limited access to expensive observation systems, satellite data can provide very useful information for this purpose. The Nowcasting Satellite Application Facility in Europe developed software to identify and track rapidly developing thunderstorms (RDT) using data from the geostationary Meteosat Second Generation satellite. The software was installed in South Africa and tested over the South African as well as the southern African domain. The RDT product was validated by means of 20 case studies. Over the South African region, validation was done by means of visual comparison to radar images as well as in a quantitative manner against the occurrence of lightning. Visual comparisons between the RDT product and images from satellite data as well as the occurrence of heavier rainfall were done over areas outside South Africa. Good correlations were found between the identified storms and the occurrence of lightning over South Africa. Visual comparisons indicated that the RDT software can be useful over the southern African domain, where lightning and radar data are not available. Very encouraging results were obtained in the 20 case studies. The RDT software can be a valuable tool for general and aviation forecasters to warn the public of pending severe weather, especially in areas where other data sources are absent or not adequate.

Highlights

National weather services such as the South African Weather Service (SAWS) have the responsibility to warn the public of pending hazardous weather events
Our goal in this paper is to show the value of rapidly developing thunderstorms (RDT) for nowcasting processes in data sparse regions, such as Africa
A few examples of the 10 cases will be shown in which the lightning data surrounding the time of the RDT product (10 min before and 10 min after) are compared with radar images at the same time of the RDT

Summary

Introduction

National weather services such as the South African Weather Service (SAWS) have the responsibility to warn the public of pending hazardous weather events. Based on inputs from numerical weather prediction (NWP) models, an advisory can be issued a few days ahead of a possible severe weather event, such as heavy rainfall or strong wind. Nowcasting implies the forecasting of weather events for the 2–6 h and relies heavily on remote-sensing tools such as satellite and/or radar systems. In many countries, especially developing and least developed countries, radar systems are too expensive to obtain and maintain.[1] In many African countries, even the basic ground-based observation systems are not adequate to provide a real-time feed of observed weather elements such as rainfall.[2] Despite the lack of enough data, the public still needs to be warned of severe weather events, which can lead to loss of life and/or property

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