Experimental probabilistic forecasts at the Storm Prediction Center

The Storm Prediction Center is responsible for providing convective forecasts across the 48 contiguous United States. These forecasts include the Convective Outlooks as well as the Tornado and Severe Thunderstorm Watches. The Storm Prediction Center also issues forecasts and products that cover convective heavy rainfall, heavy snowfall and freezing precipitation and outlooks detailing favorable conditions for wildfires. These products are enhanced by the issuance of timely mesoscale discussions and status messages that include detailed analysis and observation of ongoing severe thunderstorm activity.

The Convective Outlooks outline areas where there is a Slight, Moderate, or High Risk of Severe Thunderstorms along with an outline of where General Thunderstorms are expected. Beginning in January 1999, the Storm Prediction Center began issuing experimental Probabilistic Outlooks in an effort to provide more details in the convective forecast. These outlooks are divided up by type of severe weather expected (i.e. tornadoes, hail, and convective wind) and assign a numeric probability to the respective threat.

This paper explains the Probabilistic Outlook program at the Storm Prediction Center and will show some examples of forecast and subsequent verification made during the first year of the experimental program. The paper will also present plans for the development of probabilistic forecasts for tornado and severe thunderstorm watches.