Improving the Skill of the NWS's Extratropical Total Water Level Forecast System

One effect of the extratropical storms is storm surge, which is the water moved to shore by the high-speed winds of the cyclone. This surge, in conjunction with tidal forces, can cause severe flooding putting all who live along the coast at risk. To warn people about this hazard, the Meteorological Development Laboratory (MDL) as part of National Weather Service (NWS) developed the Extratropical Storm Surge (ET-surge) model to forecast storm surge. After the model is run, MDL uses it to provide a total water level forecast on its website (http://www.weather.gov/mdl/etsurge), to inform people about their current risk of flooding. This is done by combining the surge forecast with the predicted tide and an estimate of the amount of the water level rise due to other sources termed the “anomaly.” The total water level forecast system is the principal source of guidance for forecasting flooding caused by extratropical storms, but its accuracy had never been determined. Preliminary results show the ET-surge model and the total water level forecast to be accurate. In addition, it is also shown that the accuracy of the total water level can be improved by changing the way the anomaly is computed. Results obtained in this research project will provide information to MDL to determine possible changes to the NWS's total water level forecast system.