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Lightning is a major concern at the Kennedy Space Center (KSC) for two reasons. First, the Center is located in east Central Florida, which has one of the greatest flash densities of cloud-to-ground (CG) lightning in the country. Second, KSC employs over 25,000 individuals, many working outdoors, and maintains over seven billion dollars in facilities. With such a large safety concern, accurate forecasts of both lightning initiation and cessation are important. Lightning advisories for thirteen regions of the KSC area (Fig. 1) are issued by the U.S. Air Force's 45th Weather Squadron (45WS).
FIG. 1. The 45th Weather Squadron's Lightning Watch and Warning locations. Each circle is 5 nm (9.62 km) in radius.
Reviews of the 45WS's lightning advisories reveal that most are maintained too long. Specifically the current technique for forecasting lightning cessation requires waiting until lightning initiation parameters are no longer met. Without a better understanding of when lightning will cease, however, safety concerns dictate that lightning advisories remain in place. With an improved understanding of cessation, the 45WS hopes to employ a guideline for determining how long a lightning warning should be maintained after a particular discharge is observed. The goal of this research is to assess with a high level of confidence, whether this discharge will be the last. Shortened, but safe, lightning warning periods will result in a major cost savings from the reduction in lost manpower hours, estimated to be in the millions of dollars.
The research is using KSC's Lightning Detection and Ranging (LDAR) network. These data permit the study of intracloud and cloud-to-ground discharges within isolated thunderstorms over the KSC. With so much lightning not reaching the surface, the use of LDAR data will provide previously unknown information. For example, LDAR provides information about the last lightning flash that CG cessation studies could not consider, including whether the final flash is primarily a cloud-to-ground or an intracloud discharge. The LDAR data are augmented by CG observations from KSC's Cloud-to-Ground Lightning Surveillance System (CGLSS).
Major Objective I
The primary objective is to gain a better understanding of the lightning cessation process. Some of the questions to be answered include:
a) What is the relation between lightning cessation and total lightning activity within a thunderstorm? It is unknown whether a very active storm will have a different "cool down" period compared to a less active storm. We will determine whether lightning activity tapers off the same way for all storms or if there are significant differences between individual storms or types of storms.
b) Differences in cessation characteristics may arise due to different thunderstorm triggering mechanisms, such as shear, stability, or intraseasonal variations.
c) LDAR can detect the vertical and horizontal extent of lightning flashes. Their distribution will be analyzed for a correlation with lightning cessation.
d) Previous studies have suggested that there may be a family of curves detailing the cessation of lightning. We will determine whether a family of curves or a single statistical curve is appropriate.
e) LDAR data are combined with CG observations. This allows a determination of whether the last flash is a cloud-to-ground or intercloud flash. This is a focus that previous cessation studies could not perform.
Major Objective II
Based on results from Objective 1, we will create a lightning cessation forecasting technique for the 45WS. This technique will be an immediately usable application of the research. The technique will utilize a statistically derived period to wait after the observance of a lightning strike. If that time period has elapsed, a forecaster will be able to say with a high level of confidence that the last observed flash was indeed the last flash of the thunderstorm. The forecaster then can cancel the lightning warning that was issued earlier.
Graduate Student on this Project
Click here to view Geoffrey Stano's Ph.D. Dissertation entitled
Developing Empirical Lightning Cessation Forecast Guidance for the
Kennedy Space Center.
Click here to view Geoffrey Stano's presentation at the 1st International Lightning Meteorology Conference in April 2006 entitled Empirical Forecasting of Lightning Cessation at the Kennedy Space Center.
Click here to reach the website of 45th Weather Squadron.
Click here to reach the website of NASA Kennedy Space Center.
last updated September 7, 2006