NCEP SREF Forecasts of three Hurricanes during the 2004 Tropical Season

An examination of the National Centers for Environmental Predictions (NCEP) short-range ensemble forecast system (SREF) forecasts of four tropical cyclones during the 2004 Atlantic Hurricane season is presented. The focus is on the cyclone track forecasts and the areas threatened by heavy rains and severe weather. It will be shown that the SREF was a valuable tool in forecasting the tracks of three of the four storms presented.

In each case, the SREF offered valuable guidance in showing the areas threatened by the storms and the uncertainty in the storm tracks. It will be shown that hurricane Charlie was not well forecast. Though divergent storm tracks and cyclone speed highlight the uncertainty associated with this storm. Several SREF cycles forecast Charlie to track too far west of the observed track. This led to forecasts of heavy rain and high winds farther inland than observed from North Carolina to southern New England.

In contrast to hurricane Charlie, the SREF forecasts for several hurricanes, including hurricanes Ivan and Frances provided excellent guidance. SREF forecasts of these systems produced relatively accurate storm tracks and successfully pointed to areas threatened by heavy rains and severe weather.

The focus of this presentation will be on the SREF hurricane tracks; probabilities for greater than 25 and 50 mm of precipitation; forecasts of winds low-level winds; and convective available potential energy. This products will demonstrate potential operational products to facilitate forecasting future tropical storm using ensemble prediction system output.