A GIS-based approach to lightning studies for west Texas and New Mexico

This paper will describe cloud-to-ground (CG) lightning patterns over New Mexico and West Texas during the warm season months of May through September. Data from the National Lightning Detection Network (NLDN) for the years 1989 through 2004 (15 years) were used. ArcView GIS was used to display the spatial pattern of strikes from which several lightning hotspots are immediately apparent. The rather large initial domain then was split into two smaller domains (east and west) along the Texas panhandle/New Mexico border.

Within these domains, further investigation was conducted to examine thunderstorm initiation points, especially in relation to topographic features. Using a time lapse loop of overall lightning activity, it was found that the first strikes from newly-formed thunderstorms occurred at approximately 1800 UTC. Therefore, the NLDN data were screened for the first ten percent of strikes occurring after 1800 UTC on each day. Density maps of these flashes then were plotted (also using ArcView) to determine genesis zones. When contours of these densities were plotted over topographic data, several initiating features were identified.

To further understand the role of these topographic features, these early CG flashes were divided into wind regimes. The regime for each day was determined by the 500-700 mb mean wind from the 1200 UTC sounding for a centrally located point in each region (AMA for the eastern region and ABQ for the western region). Regimes were chosen to best capture common flow patterns based on the wind distribution for each site, and consisted of seven distinct regimes: North/Northeasterly, Easterly, Southerly/Southeasterly, Southwesterly, Westerly, Northwesterly, and Calm. Results show that some areas receive lightning regardless of wind direction, while lightning in other areas is influenced by the direction. These results then are analyzed to determine common patterns. The goal is to improve forecasting of thunderstorm initiation on days with little or no synoptic forcing. Our proposed paper will describe the above methodologies in detail, as well as present all of our results.