Latest Developments in the NWS Sea Lake and Overland Surges from Hurricanes Model

The Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model, is used by the National Weather Service (NWS) to produce storm surge guidance in several ways. SLOSH based simulation studies form the basis of the “hazards analysis” portion of hurricane evacuation planning. The Probabilistic tropical cyclone storm Surge (P-Surge) model runs SLOSH to analyze the storm surge inundation from each of its approximately 630 ensemble wind inputs. Similarly, the Probabilistic Extra Tropical Storm Surge (P-ETSS) model runs SLOSH to analyze the storm surge inundation from the North American Ensemble Forecast System’s 42 ensemble members.

One key aspect of SLOSH, for this ensemble modeling, has been its computational speed. This was due to design choices necessitated by the technology available when it was developed in the 80’s. However, SLOSH computational domains have recently become significantly broader and finer. While the results are more accurate, they take longer to run on a single processor. Additionally, NWS is working to couple a wave model to SLOSH, which will slow down the computation by at least a factor of two. To allow real-time ensemble storm surge modeling (e.g. P-Surge and P-ETSS) to continue to produce results within one hour, SLOSH needs to move from a single processor to a multi-processor program, enabling it to scale based on the number of available processors.

This paper will discuss the design changes that the Meteorological Development Lab has made to transition SLOSH into a multi-processor program and will demonstrate the impact via simulations in the south Florida SLOSH basin.