Modeling and Computations of Shallow-Water Coastal Flows

Storm surge modeling in the National Weather Service

Wilson Shaffer

NOAA

The NWS has a requirement to forecast storm surges for threatening hurricanes and to issue coastal flood watches and warnings for extratropical storms. To fulfill this requirement, the NWS developed the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model. Several products have been developed for hurricanes to aid NWS forecasters and emergency managers in planning for hurricane events and for dealing with a threatening hurricane. These include products referred to as Maximum Envelopes of Water (MEOWs) and Maximum of the MEOWs (MOMs) which give the potential flooding from various hurricanes, and deterministic SLOSH runs based on the current National Hurricane Center forecasts. More recently, the NWS developed a probabilistic storm surge product which takes into account the forecast uncertainty based on previous hurricane forecasts. In addition to SLOSH, the NWS runs an extratropical storm surge model, 4 times daily, to compute surges from extratropical cyclones. This model is similar to SLOSH, but uses wind and pressure driving forces from the NWS's Global Forecast System (GFS) model to compute water levels.

Some of the challenges and constraints of operational forecasting, and future needs of the NWS and NOAA are discussed. NOAA's recently developed storm surge roadmap to guide enhanced coastal flooding forecasting is also discussed.