Toward Improving the Wind Field Used in the P-Surge Probabilistic Storm Surge Model

The primary source of guidance used by the Storm Surge Unit (SSU) at the National Hurricane Center (NHC) comes from the Probabilistic Storm Surge Model (P-Surge), which is an ensemble of Sea, Lake, and Overland Surge from Hurricane (SLOSH) model forecasts. The P-Surge ensemble was recently upgraded (May 2021) to use improved radius of maximum wind (RMW) forecasts to define the input wind forcing. This upgrade resulted in an improvement in the probability of detection of storm surge inundation for most exceedance thresholds and better forecast reliability of the P-Surge forecasts.

However, the parametric wind profile used by the SLOSH model is relatively simplistic. For example, it does not account for wind asymmetries apart from those related to a storm’s forward motion, and the outer wind profile (r > RMW) cannot be adjusted separately via a size parameter to better match the observed 64-, 50-, and 34-kt wind radii. These and other limitations related to the wind model need to be addressed in order to extend the lead time of skillful and reliable storm surge forecasts.

In an effort to improve the SLOSH input wind field, this study will evaluate whether the Wind-speed probability model based on the gridded Tropical Cyclone marine advisory Message (WTCM) could be used to specify the input wind forcing for P-Surge/SLOSH. The WTCM wind model is designed to be consistent with NHC official (OFCL) forecast parameters. The two-dimensional wind fields from SLOSH and the WTCM will be compared, and storm surge forecasts driven by both wind fields will be evaluated.