Monday, 3 August 2015
Back Bay Ballroom (Sheraton Boston )
Convective Index is one of the most important tools to predict unstable environment and possible hazard weather using satellite information. Identifying existing convection and monitoring its evolution is crucial to minimize severe storms potential damages, specially associated with Mesoscale Convective Systems. Satellite data can provide indirect measurements of instability and moisture of a large area in short periods of time, with features detected using, for example, water vapor and infrared channels. Lightning location systems provide real time updates of storm severity evolution. Combination of satellite data and short range forecast can be even more beneficial for severe weather monitoring and forecasting. This work aims to present an objective methodology for detection and monitoring of deep convection, associated with Mesoscale Convective Systems, using different techniques and criteria for stratification of a cloud shield into areas of different intensities of convection. Temperature threshold, brightness temperature differences, and temperature trends are used as parameters for storms severity index, compared with lightning characteristics within those MCS events. The investigation is accomplished through analysis of long lived MCSs which showed that the stratification methodology is of great potential to separate areas of strong convective activity within a cloud shield, especially on highlighting very strong cases, since its initial hours of detection during lightning initiation. Comparison with radar and lightning data searching for similar patterns will be presented and also analyzed events of lightning initiation and cessation during the life cycle of the MCS. This study was applied in a operational center for nowcasting in Southeastern South America (SSA), a region comprising northeastern Argentina, Paraguay, Uruguay and southern Brazil, particularly prone to severe weather events, generally associated with Mesoscale Convective Systems with intense precipitation, lightning, hail, gust winds and some tornadoes. Lightning activity is intense in the continent throughout the year, but mostly active during the warm season (spring and summer), with maximum in the subtropical region, in this area. There is a limited knowledge in relation to the characteristics of those mesoscale severe storms including frequency, type, morphology, intensity and location of cloud-to-ground lightning associated to the occurrence of mesoscale convective systems. The objective of this study is to better understand the evolution of these storms as they occur in this area, in order to improve our abilities of analysis and forecast of severe weather events and apply directly in an operational environment.
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