Publication Date

Spring 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Climate Science

Advisor

Alison F. Bridger

Keywords

fire weather, forecasting, lightning, WRF

Subject Areas

Meteorology; Atmospheric sciences; Environmental science

Abstract

Thunderstorms are rare in coastal California during the summer months. Synoptic situations that encourage these summertime thunderstorms typically involve elevated instability that promotes dry lightning thunderstorms, where less than 0.1 in of precipitation reaches the ground. On 21 June 2008, a poorly forecasted dry lightning outbreak was responsible for starting more than 1,500 wildfires across California, and specifically the Monterey region. In this research, we used analysis data from the Global Forecast System (GFS) model to investigate the evolution of the synoptic conditions leading up to the outbreak. We then created two sets of ensembles with the Weather Research and Forecasting (WRF) mesoscale model to determine if dry convection could be simulated in areas where lightning strikes were observed. Two of the WRF-NAM ensemble members showed skill in simulating the Monterey convection. Instability and moisture fields in these simulations were also indicative of dry convection. Graupel behavior was analyzed in these simulations to determine lightning potential following McCaul et al. (2009). Overall, the convection generated by these simulations was found to be robust enough for modest cloud electrification, but recalibration that includes dry convection may be necessary to further improve this method of lightning threat detection.

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