Experimental probabilistic hazard information in practice: Results from the 2008 EWP Spring Program

The National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) has recently transitioned to "storm-based" warnings from county-based warnings. These warnings are increasingly used by graphical applications for television, the Internet, and cell phones to better communicate specific information about hazardous weather. With the rapid updates in technology and communication, the NWS can continue to build upon the storm-based warnings to better communicate specifics in uncertainty, space, and time to advanced and special-need users.

During the 6 week period of 27 April - 7 June 2008, the NOAA Hazardous Weather Testbed in Norman, OK hosted multiple visiting NWS and Environment Canada forecasters for the Experimental Warning Program (EWP). The forecasters had the opportunity to issue probabilistic guidance on several real-time severe weather events across the continental United States and an archive event from 13 August 2007 in northeast North Dakota. Each forecaster was asked to identify areas of a storm where a threat was possible, either at the current time or near future (less than 60 min) and determine a probability associated with that threat (current and at a chosen future time). The project focused on three different threats: Tornado, Hail (greater than .75 in), and Wind (greater than 50 kts). Probabilistic warning forecasts made throughout the six week period and from the archive event will be compared to the high resolution data from the Severe Hazards Analysis & Verification Experiment (SHAVE) to determine skill and reliability of the forecasts and how this guidance should be updated for future use.