Verification of Operational Storm Surge Predictions from the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) Model for Hurricanes Gustav and Ike (2008)

The Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model is used by the National Hurricane Center (NHC) to operationally predict the storm surge from tropical cyclones prior to landfall in the United States. Operational SLOSH runs generally begin with the first issuance of a hurricane watch along the U.S. coastline and use information on the tropical cyclone's size, forward speed, track, and pressure field to create a storm surge forecast for each grid box within the curvilinear, polar coordinate grid specific to the basin(s) where landfall is expected. A constant tidal level is used for the forecast and there is no contribution from wave action. Verification of the SLOSH model is dependent on the collection of a reliable dataset of water levels from gauges and high water marks (HWMs) onshore. However, it is often difficult to collect a dependable data set because of gauge failures and the distortion of HWMs on structures due to wave run-up and set-up. Since Hurricane Katrina in 2005, there has been a more organized effort to collect reliable post-storm surge information. As a result, Hurricanes Gustav and Ike in 2008 have large surge data sets. This study compares the surveyed maximum surge information from gauges and HWMs for Hurricanes Gustav and Ike to operational SLOSH runs created 12, 24, and 36 hours prior to landfall which were used to construct the surge statement in NHC's Public Advisory product.