A high resolution air-lake coupled model is being developed to improve operational marine forecasts in the Great Lakes region. The atmospheric model is a workstation version of the Eta model. The lake model is a modified form of the Princeton Ocean Model. The coupled system is currently being run twice daily at 12 UTC and 00 UTC on a PC at NWSFO-DTX in White Lake Michigan and provides 48 hr forecasts for Lake Huron. The horizontal resolution of the coupled model is 10 km. The model provides hourly forecast output of the standard atmospheric variables as well as a suite of marine output including significant wave height, period, and direction and three-dimensional lake-velocities and temperatures. Output from the coupled system is available five to six hours after each run cycle and can be displayed and analyzed using AWIPS, so forecasters on shift can evaluate and use the information in real time.

Marine output from the coupled system is compared to that from an uncoupled version of the system at similar resolution as well as to output from the Great Lakes Forecasting System, which utilizes output from the 32 km Eta to force a (uncoupled) wind-wave model. Examples from different synoptic situations are presented. The coupled system is superior to the non-coupled models, especially when rapid changes in lake surface temperatures (e.g., caused by upwelling) develop during the forecast period.