A Study of the Characteristics of Thunderstorm Cessation at the NASA Kennedy Space Center

A Study of the Characteristics of Thunderstorm Cessation at the NASA Kennedy Space Center PDF

Author: Michael Shawn Hinson

Publisher:

Published: 1997-07-01

Total Pages: 103

ISBN-13: 9781423571025

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A lightning summary was developed for a 100x100 kilometer area centered at the NASA Kennedy Space Center. Spatial and temporal patterns, and first stroke peak currents were analyzed from 1986-1995. Three thunderstorms were chosen due to their proximity to the Kennedy Space Center (KSC) and examined for their end of storm characteristics. Radar echoes at the -10 deg C and -20 deg C temperature heights were associated with cloud to ground (CG) lightning strike locations from the National Lightning Detection Network. Electric fields were also examined during the same time frame for any correlations. A pattern was observed for the spatial distribution of CG lightning. An inland maximum in ground flash density was observed during the summer months for both negative and positive flashes. The summer months had the lowest percentage positive flashes (2.5%) while the maximum value occurred during the winter (11.4%). Although thunderstorms can occur at any time during the day, the diurnal distribution of lightning flashes showed that the afternoon (2000 UTC) was the time of maximum lightning activity. From a time history of radar echoes, it was found that a 45 dBZ echo, last detected at the -10 deg C temperature height, may be a good indicator of the end of lightning activity. The observed lag times between this lightning termination signature and the end of all CG lightning flashes was 30 min for all three thunderstorms.

Techniques for Forecasting the Cessation of Lightning at Cape Canaveral Air Station and the Kennedy Space Center

Techniques for Forecasting the Cessation of Lightning at Cape Canaveral Air Station and the Kennedy Space Center PDF

Author: Michael W. Holmes

Publisher:

Published: 2000-03

Total Pages: 90

ISBN-13: 9781423534105

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The focus of this research effort is directed toward identifying new methods of forecasting the cessation of lightning along the Central Atlantic Coast of Florida. Cloud-to-ground lightning flashes place Air Force (AF) personnel and assets at risk almost daily at this location. Providing a more accurate method of forecasting the cessation of lightning would allow for safer and more efficient execution of AF operations. A data set consisting of 40 thunderstorm cases was identified within a 90 nautical miles (nmi) region surrounding the Melbourne, Florida WSR-88D (KMLB) site. Each case falls between the months of May and September and the years of 1995 through 1997. Simple and multiple linear regression models are built using this dataset. Variables included max Vertically Integrated Liquid water (VIL), max reflectivity, max peak current, peak cumulative flash rate, peak negative flash rate, and peak positive flash rate. Results indicate that three of the simple linear regression models to some extent accurately represent the data. Additionally, when the data set is separated by thunderstorm cell type (multi or single) and cell specific regressions are built, results indicate that the regressions based on the single-cell data set produce a substantial increase in forecast skill compared to that of climatology. In fact, some regressions are shown to improve forecast accuracy by 90% over that of climatology. Moreover, multiple linear regression models are shown to produce similar results and further reinforce the notion that each thunderstorm cell type (multi or single) behaves substantially different from the other with respect to forecasting the cessation of lightning.

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