Creating Inundation Guidance from NWS's Extra-Tropical Storm Surge Model

In the 1990's the National Weather Service's (NWS) Meteorological Development Laboratory (MDL) applied the Sea Lake and Overland Surges from Hurricanes (SLOSH) model to Extra-Tropical storms by (a) using the Global Forecast System (GFS) winds as input and (b) removing the computation of inundation based on storm surge in order to improve computational efficiency. The result was the Extra-Tropical Storm Surge (ETSS) model which is run operationally four times a day to predict storm surge along the U.S. East Coast, Gulf of Mexico, West Coast and all of the coasts of Alaska.

Overland surge guidance for extra-tropical storms is now desired in support of storm surge watches and warnings critical to low-lying coastal communities. In response, MDL has enhanced the ETSS model to predict the extent of overland flooding by: 1) Re-introducing the inundation algorithm based on surge 2) Incorporating a tide algorithm to allow inundation based on surge and tide 3) Nesting the tropical and extra-tropical computational grids to leverage the finer overland details contained within tropical grids

This paper will describe details of this effort. Simulations of historical events with and without these enhancements will be discussed.