On Upgrading the Probabilistic Storm Surge Ensemble for NHC Operations

During a hurricane landfall, storm surge is a significant threat to life and property in coastal regions. The Storm Surge Unit (SSU) at the National Hurricane Center (NHC) is responsible for predicting and communicating the storm surge risk during tropical cyclone events. In particular, the real-time products issued by the SSU are used by the emergency management (EM) community to facilitate life-safety evacuation decisions. Growing coastal populations and long evacuation clearance times require EMs to have more accurate storm surge forecasts at longer lead times.

Currently, NHC uses the Probabilistic Storm Surge Model (P-Surge) within 48-hours of landfall to assess the storm-specific inundation risk. P-Surge output is a statistical evaluation of an ensemble of storm surge simulations conducted using the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model. The 500-1000 member ensemble is based on the current NHC official forecast and takes into account historical errors (5-year average) in official NHC track and intensity forecasts. In order to provide high fidelity storm surge forecasts at 72-hour lead times, the SSU is working on fundamental research to improve the P-Surge ensemble. The goal is to better constrain the P-Surge ensemble with inputs such as wind structure information, now possible because of advancements made in hurricane modeling as a result of the Hurricane Forecast Improvement Project (HFIP). This presentation will summarize the future of probabilistic storm surge forecasting to meet the NHC/SSU end-user requirements.