Principal Investigator: Dr. Mark D. Powell
Objective: To serve as scientific operations officer for the Marine Olympic Weather Support Forecast Center.
Rationale: With over 3000 athletes, coaches, organizers, officials, and spectators located anywhere from 1-4 miles offshore for periods of up to 10 hours, Olympic Sailing represents the most weather exposed event in the 1996 Summer Games. Besides providing timely warnings of severe weather, the Marine Olympic Weather Support facility will also provide short term forecasts of wind and wave conditions and heat index with rapid updates. Because of his national and international experience in competitive sailing, the PI serves as a liaison between the sailing community and the forecast center, helps design forecast products and logistics, and conducts studies of the local climatology to help develop forecasting guidelines.
Method: Forecasting wind conditions for the yachting events of the Olympic summer games will require using sophisticated mesoscale atmospheric numerical models together with the knowledge of a staff of meteorologists with considerable marine forecasting and sailing experience. With the exception of specialized private forecast services similar to that provided for the America's Cup competition, mesoscale models are not normally used to provide detailed, hour-by-hour, local area wind forecasts; hence the models will need to be evaluated against climatology and persistence to determine whether they demonstrate skill. Since the forecast team comprises individuals from several states outside the venue area and includes members from Canada and Australia, it is important that the forecast team become familiar with the local conditions expected for the time of the Olympics. The Marine Olympic Support Forecast Center (MOSFC) will be issuing forecasts and briefings to the athletes and coaches of all participating nations in addition to race officials and venue managers. Knowledge of the atmospheric and oceanographic climate of the competition venue will assist these users with precompetition planning and training.
Accomplishment: Climatology suggests that the sea breeze will be the dominant wind pattern during the competition. In order to learn more about the expected oceanic and atmospheric conditions, as well as sea breeze development and evolution off Savannah, a study was initiated using observations collected in the summer of 1994 by a special olympic buoy sited by the National Weather Service (NWS) within one of the race courses and by an automatic weather station sited by the University of Georgia on a barrier island adjacent to another of the race courses. These data were compared to nine years of measurements collected from 1985-1993 at the NWS Savannah Light Coastal Marine Automated Network (C-MAN) platform located roughly 22 km offshore. The typical wind behavior consists of a weak offshore south westerly that decreases to a minimum between 10 and 11 am local time and then backs steadily while increasing to 12-14 kts from the south-southeast by 4 pm. The sea breeze direction is roughly 165 which is essentially perpendicular to the general coastline shape. The backing with time is indicative of a mixture of the developing sea breeze with a background gradient flow associated with the Atlantic High pressure cell. Veering of the sea breeze with time is only evident after 5 pm local time and persists through the evening while gradually being transformed into a land breeze during the early morning hours. Analyses suggest that the sea breeze extends well offshore and its evolution is dependent on the background synoptic situation. The coastal and offshore wind behavior is also being evaluated as a function of heating over land, thunderstorm activity, cloud cover, the tidal cycle, the difference between land and sea surface temperatures, and the pressure field.
Key reference:
Powell, M.D. Wind forecasting for yacht racing at the 1991 Pan American Games. Bulletin of the American Meteorological Society, 74(1):5-16 (1993).

Last modified: 10/25/96