S161 Analysis of High Intensity Positive Cloud-to-Ground Lightning Strikes over Eastern Colorado

Sunday, 6 January 2019
Hall 4 (Phoenix Convention Center - West and North Buildings)
Megan Franke, Metropolitan State University, Denver, CO

Every year lightning strikes cause billions of dollars in damage to societal infrastructure and countless fatalities. Within these dangerous strikes, the positively charged cloud-to-ground strokes cause more damage than any other type of lighting. Vaisala’s National Lightning Detection Network (NLDN) has been in operation since 1989 and fortunately, due to the constant improvement that it has undergone during this time, it has proved to be extremely reliable in lightning detection for the public, private, and governmental sectors in our country. This ground based lightning location and protection network has the capability of detecting cloud-to-ground strikes, defined as a stroke, versus cloud-to-cloud strikes (or pulses), longitude and latitude, error ellipse, peak amplitude, as well as polarity. The benefit of research with this dataset could lead to an improved understanding of the occurrence and formation of potentially dangerous positive lightning strikes within a severe storm lifecycle.

This study will utilize three years of NLDN data of positive strokes over the eastern half of Colorado, starting at the Rocky Mountains and extending to the Colorado border. As the warm season is the most active thunderstorm season in Colorado and has the highest flash densities, the months of June, July, and August will be analyzed. The areas of interest are the Cheyenne Ridge, Palmer Divide, the Raton Mesa, and the Plains in eastern Colorado. The acquired data will first be sorted by polarity of the stroke. Then, once all the positive strokes for the area are accumulated, density maps will be created, making it evident where positive cloud-to-ground strokes most often occur. After spatial analysis of positive strokes has been done on the area, a more in-depth analysis will occur for storms initiating off or near the Palmer Divide. Archived radar data will be used along with SPC storm reports to acquire numerus severe and nonsevere storms that initiated in that region. Ten storms, five that became severe and five that did not become severe will be filtered through the NLDN via data, time and latitude/longitude. Utilizing the Rapid Refresh (RAP) model data, skew-T diagrams will be constructed in the proximity of the densest lightning strokes to analyze the thermodynamic properties of the environment at that time. The atmospheric parameters/processes that will be analyzed and investigated are normal convective available potential energy (NCAPE), moisture distribution in the vertical, the freezing level, lifted condensation level (LCL) a proxy for cloud base height, equilibrium level (EL), and cloud depth. The focus of this study is to formulate a relationship between lightning polarity and the environment of the atmosphere in which they might occur, with the hopes of better understanding the anomalous (inverted) charge structures that frequently develop in Colorado thunderstorms during the peak warm season.

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