| November 7, 2002 NEW METHOD STRIKES AN IMPROVEMENT IN LIGHTNING PREDICTIONS A new lightning index that uses measurements of water vapor in the atmosphere from Global Positioning Systems has improved lead-time for predicting the first lightning strikes from thunderstorms. The index will help greatly aid NASA Space Shuttle launches at Kennedy Space Center, Fla, and other commercial and U.S. Department of Defense launches from Cape Canaveral Air Force Station, Fla. “Better forecasting and more advance warning of lightning strikes will help reduce the delays or cancellations of shuttle launches from Kennedy Space Center (KSC),” Steven Businger of the University of Hawaii, Honolulu, said. Nearly 75% of all space shuttle countdowns between 1981 and 1994 were delayed or scrubbed, with about one-half of these due to weather. The new Global Positioning System (GPS) Lightning Index combines data on the changing amount of water vapor in the atmosphere from a GPS receiver site with other meteorological data. One GPS receiver is located at the KSC on Florida’s east coast. “According to the National Lightning Detection Network, the region where KSC is located has one of the highest lightning flash densities in the country, which makes this new Index extremely valuable,” said Robert A. Mazany, also of the University of Hawaii. Mazany and Businger worked with Seth Gutman at NOAA’s Forecast Systems Laboratory in Boulder, Colo., and William Roeder at the 45th Weather Squadron, Patrick Air Force Base, Fla., on the new GPS Lightning Index. Warm moist air from the Atlantic Ocean and Gulf of Mexico provides the needed fuel for summer thunderstorms occurring almost daily over Florida. Southwest airflow accounts for two-thirds of the lightning strikes during the summer at KSC. Southwest flow collides with the east coast sea breeze and forces the warm moist air to suddenly rise and form thunderstorms over east central Florida. Then those same southwest winds push the thunderstorms eastward over KSC. It’s important to look at water vapor in thunderclouds because water and ice molecules help to create the positive and negative charges in a thundercloud that generate lightning. Warmer air tends to hold more water droplets. When there is enough of a difference in the positive and negative charges in a cloud, lightning results. An important weather challenge is to forecast lightning within a 20 mile radius of the launch complexes, 1-8 hours before a first strike, depending on the operation being supported. For instance a Shuttle landing requires a 90 minute lightning forecast, whereas the movement of solid rocket boosters requires a four hour forecast, and the movement of the Shuttle to the launch pad requires an 8 hour forecast. Benefits of better forecasts include the safety of personnel and protection of multi-billion dollar rocket launching systems, payloads, and supporting infrastructure. Accurate lightning forecasts can save $1M by avoiding either a 24 hour launch delay or the need to land the Space Shuttle at another facility and transport it back to KSC. Businger said that data from the 1999 summer thunderstorm season was used to test the Index. The Index combines four predictors, including a prediction tool of atmospheric electric charge, the amount of water vapor detected in a cloud or air mass, the change in the amount of that water vapor over 9 hours, and a scale called the “K Index” that predicts how unstable the air will become. During initial testing, the new index improved the lead-time for lightning strikes by nearly 10% at the Kennedy Space Center. When Businger matched the index with meteorological conditions from the summer of 1999, results revealed a 26% decrease from the KSC’s previous season’s false alarm rates. The GPS Lightning Index provides useful guidance to forecasters for preparing lightning forecasts, when combined with other resources such as radar and satellite data. Further testing will continue to consider using the index to also forecast related weather hazards such as heavy rain and flash flood events. The article, “A New Lightning Prediction Index That Utilizes GPS Integrated Precipitable Water Vapor,” appears in the October 2002 issue of the American Meteorological Society’s Weather and Forecasting. This research was supported by the U.S. Air Force and NOAA. Additional funding was provided by NASA and the Department of the Navy, Office of Naval Research under the Pacific STARNET program. ###
Contacts:
Robert J. Gutro
NASA Goddard Space Flight Center
Rgutro@pop900.gsfc.nasa.gov
Tel. 301-286-4044
Bruce Buckingham
NASA Kennedy Space Center
Bruce.Buckingham-1@ksc.nasa.gov
321-861-7642
James Manke
Univ. of Hawaii
Manke@hawaii.edu
Tel. 808-956-6099
Barbara McGehan
NOAA
Barbara.Mcgehan@noaa.gov
Tel. 303-497-6288
Stephanie Kenitzer
American Meteorological Society
Tel. 425-432-2192
kenitzer@dc.ametsoc.org | |
 Lightning Strikes the Launchpad Before the Launch of STS-8 An electrical storm created a tapestry of light in the skies near Launch Complex 39A at the Kennedy Space Center, Florida prior to launch of the Challenger. In this picture, a bolt of lightning appears to be striking the complex itself while the orbiter sits on the pad, illuminated by flood lights. Florida has the most lightning strikes in the United States. Around Kennedy Space Center, the average square mile is struck directly by ground to cloud lightning on an average of 42 times per year. Better lightning predictions could improve public safety. Lightning is the number two weather killer in the US. Lightning is the number one weather killer in Florida. CREDIT: NASA MSFC, KSC, JSC  Worldwide Map of Lightning Hits A map created by scientists at the National Space Science and Technology Center is offering an animated glimpse of lightning activity worldwide, with each frame representing the average lightning activity on a single day of the year. CREDIT: NASA/MSFC  Lightning Map Data from space-based optical sensors reveal the uneven distribution of worldwide lightning strikes, with color variations indicating the average annual number of lightning flashes per square kilometer. The map includes data obtained from April 1995 to March 2000 from NASA’s Optical Transient Detector; and from December 1997 to November 2000 from NASA’s Lightning Imaging Sensor (LIS). For more information, click here. CREDIT: NASA/MSFC  Lightning Views From Space There are more than 2,000 thunderstorms taking place around the world at any given instant. This view was taken aboard the space shuttle. Scientists have a variety of tools for studying lightning including satellites, weather balloons, airplanes, and computer models. Better lightning predictions could improve public safety and benefit construction companies, amusement parks and utilities. CREDIT: NASA/MSFC  Water Vapor Data Set Animation Moisture is the fuel that drives thunderstorms. Scientists use weather balloons and satellite data to monitor moisture in the atmosphere. The moisture data is incorporated into weather and climate models for predicting storms and lightning strikes. CREDIT: NASA/Goddard Space Flight Center Scientific Visualization Studio  Reading the GPS Lightning Index Graphs These are graphs generated from the GPS Lightning Index. The scale on the left (the Index) ranges from zero to 1. The flat line across the 0.7 reading indicates a “threshold.” Any graph line that falls under that threshold indicates that lightning may strike. There are several days represented in the graphs, July 5th, 15th and 18th, where there were no lightning strikes projected, and July 3rd and 10th, and August 1st, days with lightning in the skies around the Kennedy Space Center. CREDIT: University of Hawaii  Lightning Sensor Distribution The top map depicts the location of meteorological sensors in the vicinity of Cape Canaveral Air Station and the Kennedy Space Center. Circles indicate the primary areas of concern for lightning strikes. The bottom map depicts current and planned Global Positioning System sites throughout the state of Florida. CREDIT: University of Hawaii |
