Advancing Marine Forecasting Capability with Lightning Density and Overshooting Top Detection

Beyond the range of land-based radar, some of the biggest hazards to mariners are caused by severe thunderstorms. Vessels of all sizes are exposed to rapidly changing conditions in visibility, wind speed and direction, wave heights, and lightning. With the impracticality of surface-based radar over water, and the irregularity of ship-based observations, marine forecasters must rely on remotely sensed data. Although satellite imagery provides large scale ocean coverage, the land-based lightning detection systems do not detect all lightning activity occurring over the ocean, especially far from land. The Tropical Rainfall Measurement Mission (TRMM) satellite does contain a Lightning Imaging Sensor (LIS) that provides 90 second lightning data, but only over a small portion of the Earth in an orbit that peaks at 38N and 38S latitude. More reliable marine lightning data would allow forecasters to better understand and more accurately predict thunderstorm development and maintenance over the oceans, and provide critical information to vulnerable ships at sea. In an effort to advance marine forecasting capability, a joint effort among the National Weather Service (NWS), Ocean Prediction Center (OPC), National Environmental Satellite, Data, and Information Service (NESDIS) Center for Satellite Applications and Research, and the University of Maryland's Cooperative Institute for Climate and Satellites (CICS) developed a lightning density product using the Vaisala GLD-360 lightning feed as part of the Geostationary Operational Environmental Satellite R-series (GOES-R) Proving Ground, in preparation for the Geostationary Lightning Mapper (GLM). An additional GOES-R product, the Overshooting Top Detection (OTD) is being used with the lightning density product to analyze thunderstorm behavior in the OPC Offshore Zones. To prepare OPC forecasters for the implementation of this new data, a series of case studies were created using the lightning density and overshooting top products. The case studies evaluate convective outbreaks between the months of October and March in OPC's North Atlantic forecast zones for trends in lightning density and OTD as they relate to convective mode in the cool season. Knowledge of these patterns may aid OPC forecasters in utilizing these new products to produce more precise marine thunderstorm statements.