Bridging the Watch to Warning DSS Gap with Lightning Derived Petals

Lightning data is being used to bridge the gap between watches and warnings at the National Weather Service (NWS) Forecast Office in Tulsa, Oklahoma. A system was devised to use lightning data every ten minutes to compute the probability that severe convective warnings will be issued. The ultimate goal is to provide Decision Support Services to emergency managers, law enforcement agencies, school systems, and others. Lightning data and storm motion data from ongoing convection is gathered from the NWS AWIPS database and is used to produce gridded fields of the probability of future convection. These probabilities are combined with fields for the conditional probability of being in a severe convective warning. The product of the two fields is the unconditional probability of severe convective warnings, which gradually increases as a storm approaches any particular grid point. The system bridges the gap between convective watches and warnings, enhancing the Weather Ready Nation. The system was first developed in 2010 as a cooperative effort between Oral Roberts University and the NWS Tulsa Forecast Office. The system uses a combination of mathematical functions to produce petals or plumes of probabilities. The probabilities nearest the observed lightning are near 100% and diminish based on a gamma distribution. The gamma distribution is adjustable based on the storm motion and can also be adjusted based on meteorological parameters. This system provides almost continuous updates on the probability of a severe convective warning to localities downstream of ongoing convection. Additionally, the system helps forecasters make short term updates to the basic probabilities of precipitation and thunder. An explanation and summary of the system will be provided along with examples of its products.