SUPPORT FOR THE SAILING EVENTS OF THE 1996 SUMMER OLYMPIC GAMES
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