VAWS: Assessing Freezing Spray Algorithms

Speaker: Gene Petrescu, NWS Alaska Region Arctic Test Bed.

Freezing Spray is the leading cause of marine fatalities in Alaska waters. Notable events of vessel sinkings due to freezing spray include; The Scandies Rose, Destination, Hunter, and Star Trek. Freezing spray can accumulate quickly in extreme events and result in rapid destabilization of a vessel. The National Weather Service has been using the Overland Method to estimate freezing spray accumulations for a few decades. Canada uses the Stallabras Method which is fairly similar. A challenge is that there is very little data to evaluate how well these algorithms work in various weather / water conditions. They were developed using specific vessel classes in specific regions, such as the Overland in the Bering Sea. How well does this apply to the Gulf of Alaska? The first phase of the project is attempting to use multiple methods to obtain in-situ freezing spray observations. A first set of observations were successfully collected early in 2024, with the observation period continuing through the upcoming winter. These observations will be used to evaluate the algorithms and help us determine their utility in varying conditions, or if they need to be adjusted how they should be improved. We will describe the characteristics and challenges of forecasting freezing spray, the partnership with AOOS, Skippers Science, AXIOM, and the Alaska Marine Exchange in collecting observations, and the next steps for algorithm evaluation.