Univ. of California (Los Angeles): "A study of Bering Sea storms and their associated storm surges on Nome, Alaska"

Final Report

The most significant forecasting problems in the area of the Seward Peninsula in Alaska, and in particular the city of Nome, include low stratus and fog, orographically induced precipitation, topographically affected winds, and coastal flooding. This project was a first step in consolidating and expanding existing meteorological knowledge associated with these forecast issues by examining Bering Sea storms that cause extensive damage to the shoreline.

Nome has been subjected to flooding on several occasions in the past. In recent times, the storm event of October 5-6,1992 caused several million dollars in damage. This storm was not particularly deep, and its track was farther to the west than would be expected to produce such damage. In addition, there was no ice and tides were not especially high. Investigation of this storm and two others with very different characteristics included the following objectives:

• Improving the scientific understanding of Bering Sea storm surges on the part of NWS forecasters
• Developing new and improved techniques for operational forecasting of Bering Sea storm surges, resulting in more accurate and timely warning of the affected public
• Initiating and developing a scientific relationship between UCLA and the NWS Alaska Region

The results of a comprehensive review of previous studies of western Alaska storm surges suggested that significant additional progress in forecasting these surges would require the use of a dynamical forecast model. A request was made to the NWS Techniques Development Laboratory to adapt their Extratropical Storm Surge Model to coastal western Alaska. The model output was verified against the observational data and analyses.

The model performed well for the October 1992 and September 1993 (a "reverse" event in which offshore winds drove water out of Norton Sound) events, but did not adequately replicate the August 1993 case which was a near-miss surge case. Further examination of the latter case revealed that the storm moved too fast for the adequate model spin-up to occur.

The case study results, along with the evident superiority of the surge model forecasts over those from the much simpler statistical model previously used, led to the operational implementation of this storm surge model in Fall 1995. The resulting significant benefits to the operational NWS forecasting and warning activities of the NWS Alaska Region were a direct consequence of this Partners Project.