Authors

Michelle Wilson

Document Type

Internship Report

Publication Date

Spring 2013

Abstract

The results presented in this study will allow forecasters in the NWS Miami Weather Forecast Office, in a more quantitative basis, to increase their knowledge on the atmospheric conditions suitable for active lightning days and provide a better understanding of the performance of the Florida State University/Florida Power and Light Corporation (FSU/FPL) model in predicting lightning. The FSU/FPL model produces statistically-derived forecast spatial fields of categorical lightning occurrence at various times throughout the day using meteorological parameters as input. This presentation will outline how the lightning forecasts for the 2012 convective season (1 June-30 September) were analyzed in two ways: 1) comparing the forecast lightning from the FSU/FPL SREF model to the observed lightning from the National Lightning Detection Network in South Florida; and 2) analyzing the weather conditions that caused the highest frequency of lightning. The FSU/FPL model predicted 53% of all the lightning in the highest probability range for 15Z, 67% of all the lightning for 18Z, and 57% of all the lightning for 21Z in the highest probability range indicating that the model was able to predict the general area where lightning was observed for the 2012 convective season. Large fluctuations in 500 mb temperature can explain one of the impmiant physical processes related to lightning activity over South Florida. Decreases in 500 mb temperatures were generally correlated with an increase in lightning activity. However, a decrease in 500 mb temperature did not result in an increase in lightning activity if sufficient moisture was not available, if cloud cover inhibited surface heating, or if the surface wind speeds were too strong to allow for intensification of sea breeze fronts. Diagnosing the 500 mb temperatures alone was not sufficient to explain why lightning occurred on certain days but not others, as there are many atmospheric variables to consider. The combination of low 500 mb temperatures with a moist air mass at the leading edge of a Saharan air mass led to increases in lightning activity in South Florida. In addition to these results, images of detailed weather patterns intended to help the NWS Miami forecasters identify the days with the greatest potential of active lightning will be presented.

Comments

Department: MPO

MPS Track: WFC

Location: National Weather Service - Miami Weather Forecast Office

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