The National Weather Service Spaceflight Meteorology Group provides lightning warning and watch products for NASA's Johnson Space Center. The lightning warning (called a Lightning Alert) provides notice that lightning is either imminent or observed to be occurring within six miles of JSC. The lightning watch (officially called a Lightning Advisory) provides customers with a forecast of lightning occurrence within the warning area with a goal of providing 30-minutes lead time for lightning events. The lightning watch is limited to those customers needing time to prepare for the onset of lightning conditions. An “all clear” is issued for the lightning warning when lightning has not occurred within the previous 30-minutes, while an “all clear” is issued for the lightning watch when the forecaster determines there is no credible threat of lightning occurring within the warning area.

The lightning watches are routinely verified in order to assess the quality of the products. Forecasters issued 209 lightning watches between February 2005 and June 2008. Fifty-two percent (108 of 209) of the watches were issued with positive lead time. Eighteen percent (38 of 209) of the watches were issued with no lead time when the first lightning strike occurred within the warning area. Thirty percent (63 of 209) of the watches were false alarms for which no strokes were detected by the National Lightning Detection Network (NLDN) within the warning area. The average lead time between the issuance of the watch and the observation of lightning was 28 minutes. The average duration of a lightning watch was 1 hour and 59 minutes. Two watches exceeded 8 hours which potentially implies the watch impacting operations for an entire workday.

Overall, the lightning watch and warning program has been very successful. During this time period, only one person at the Johnson Space Center was injured in a lightning-related incident. A guard who had followed the local safety policy and sought shelter upon issuance of a lightning watch was injured when lightning struck nearby. It was not clear if the lightning struck the structure or if current may have conducted into the structure through power or other cables. Weather safety is included as in the annual training of Johnson Space Center staff, and outdoor events are required to identify weather support requirements. The Spaceflight Meteorology Group has provided tailored weather support for several events conducted at Johnson Space Center including balloon festivals and large outdoor gatherings.

Two of the significant challenges that remain are providing better guidance to forecasters for determining the end of the lightning threat and improving customer response to the lightning watch and warning. The time between the last observed lightning stroke and the issuance of the “All Clear” for the watch can have a significant impact to customer operations. More effective forecasting rules-of-thumb relating radar observations to the end of the lightning threat are needed. In addition, improved mesoscale observations and forecast tools may be needed to more accurately predict convective initiation for those cases when storms in the local area create uncertainty in the short-term forecast. Customer response could also be improved. “Close calls” have been reported when customers have been observed to continue working outside after a lightning watch or warning had been issued. Either the products were not communicated to customers or the customers chose not to take precautions based on the watch or warning. Further efforts to understand where the watch/warning process failed is needed.