Hurricane Storm Surge Forecasting

The National Weather Service (NWS) has developed a hurricane storm surge model called SLOSH (Sea, Lake, and Overland Surges from Hurricanes) to compute hurricane storm surges, given storm data as input. The numerical model incorporates a dynamic coastline, overland flooding, and sub-grid features such as barriers, cuts between barriers, and one-dimensional flow along channels of varying width. The SLOSH model has been applied to most of the United States\´ Gulf of Mexico and Atlantic coastlines vulnerable to hurricanes. A description of the model\´s use and limitations for hurricane storm surge forecasting is presented. Some specific examples of the use of SLOSH are drawn from Hurricane Elena, 1985. In addition to SLOSH\´s use for real-time surge forecasting, SLOSH is used extensively in hurricane evacuation planning. The model is run with several hundred hypothetical hurricanes, selected according to an area\´s climatology. The model generates the flooding expected for each storm. Combining these flooding patterns helps to determine an area\´s vulnerability to hurricanes. Also, model-generated winds assist planners in determining when evacuation routes may be shut down due to high wind. State and local agencies integrate this information with population studies and road capacity estimates to develop a comprehensive evacuation plan. One outcome of such a plan is the "evacuation time"--the lead time needed for a safe evacuation of a coastal area from an impending hurricane.