An Ultra-High Resolution Sailing Forecast System for San Francisco Bay

The San Francisco Bay is arguably one of the best places to sail in the world, with strong tidal current and a sea breeze in excess of 20 knots nearly every summer day. Cold, upwelled Pacific waters on the coast and hot temperatures in the Central Valley drive a strong sea breeze, amplified and steered by topographic features like the Golden Gate, Alcatraz Island, and Angel Island. Conversely, fickle wintertime winds often make even getting around the race course a challenge. Competitive sailors are able to utilize even small changes in wind speed and direction as a competitive advantage. We have created a 200-m resolution daily WRF wind forecasting system, including a unique visualization system relying on PostGIS and Geoserver to deliver just-in-time forecasts to sailors. The forecasts were used to obtain a 1st place in every major race in 2014. This talk describes the WRF configuration and post-processing used to create the forecasts, in addition to wind field validation. We also explore the improvements made to the forecasts when smartphone barometric pressure observations are assimilated into the forecast.