Electrical and hydrometeorological studies of severe thunderstorms in the south of Brazil

The operational suite in weather forecast offices has changed a lot in the past few years. Besides conventional meteorological information, the recent development and implementation of many new in situ and remotely sensed observations such as satellite, weather radars, and lightning detection networks has resulted in a wealth of meteorological products for weather forecasters with the supply of vital information in real-time. However, the forecaster's ability to manually integrate these data into a comprehensive analysis of the current state of the atmosphere is hindered by the volume of data and the differing characteristics of the various observing systems.

For severe weather monitoring and forecasting, information obtained from lightning detection networks, radars and satellites are considered most important. Lightning detection networks and radars are capable of storms surveillance with shorter time intervals between observations covering an area over a few hundred kilometers while the integration of lightning data with Doppler weather radar and meteorological satellites provides meteorological surveillance for a larger area and in real-time. Lightning detection systems allow for the surveillance of electrically active storms on areas larger than that covered by a weather radar, but it is not yet possible to evaluate spatial and temporal evolution of the storm quantitatively. With a Doppler weather radar, hazard storm potential (e.g. flash flood, hail, strong wind, tornado), precipitation estimation and forecasting (in conjunction with numerical weather prediction models) are already possible.

The experience of lightning data analysis and severe weather monitoring and forecasting in a meteorological operational center is discussed. Located in a region particularly prone to hazardous weather events (intense lightning and precipitation, hail, flash floods and others) in the south of Brazil, SIMEPAR operates and maintain a hydrometeorological system with a S-Band Doppler weather radar, automatic hydrometeorological network, satellite reception and processing, and also integrates the Brazilian Lightning Detection Network with the management and distribution of lightning information for several operative end users.

This paper presents results of the analysis of electrical and hydrometeorological characteristics of severe storms, especially with strong lightning incidence, hail and intense precipitation observations during events in the south of Brazil. Although thunderstorms with strong precipitation and intense wind gust associated to intense lightning activity (cloud-to-ground strokes) of negative polarity are the most common, positive lightning storms such as presented here are related to strong severe weather events and are not uncommon in this region. The set of storms analyzed and presented here have no indication of tornadoes. However, other cases will be investigated in the future to analyze more carefully these severe weather events.