San Francisco Bay Racing Overview

By Bill Barton With material borrowed from Bob Marshall

The Olympic Circle off the shores of Berkeley, California offers a great arena for one design racing. You will likely be able to reach in and out to the racecourse from the Richmond Y.C. The end of August and first week of September marks the beginning of a transition period in the weather. The shift is from the San Francisco Bay "summer" of morning fog and afternoon building westerlies to an autumn period or pattern of much less fog and more moderate land-breeze/sea-breeze cycles typical of other coastal locations. The often-quoted line from Mark Twain, "the coldest winter I ever experienced was a summer in San Francisco", is out the window by September! Expect light to moderate conditions with generally flat water.

It is particularly important to keep your head out of the boat this time of year. You need to be aware of what the pressure looks like at the Golden Gate Bridge ("The Gate"), what the hillsides of Mt. Tamalpais are showing weather and fog wise, what Angel Island and boats cruising in Raccoon Straits are showing, and finally, you need to give some vigilance to possible northerly pressure that may be lurking beyond the Richmond/San Rafael Bridge ("North. Bay"). In September these clues are very important to attend to and can really help you anticipate significant shifts on the racecourse. Weather patterns can stagnate for two weeks or more.

In early September there may be some days with late clearing fog and strong afternoon westerlies through "The Gate". These conditions occur when the Central Valley, fifty miles to the east, is blistering in 90 degree plus and is creating an area of thermal low pressure, and the Pacific high is directly off the coast. There is a resultant steep west to east pressure gradient and the wind can smoke (18 - 25 knots) on the Bay and Circle. This time of year, however, it is way less probable.
When the onshore wind is deflected along the contours of the Bay, the direction is typically south of west on the Circle. Generally you can expect 185 to 190 in the am going to 210 and 220 in the afternoon. The Circle is shallow with much of it in the ten to fifteen feet area. Being shallower than the water to the west, a steep chop can be generated when a strong westerly is in and when the ebb tide is operating.

As September rolls out there are more and more Indian Summer type days characterized by moderate breeze. When high pressure builds into Oregon and Idaho, an offshore flow keeps fog well away form the coast and the temperature of the Circle water can jump into the low seventies instead of in the summer's fifties. When this happens the sea breeze will be predictably later to fill on the Circle and will peak out in the 12 to 15 knot range rather than the 22-knot plus winds of August. In an ebb tide race, particularly watch out for large wholes in the breeze late in the day with huge shifts in them.
The average San Francisco temperature for the first half of September is 68 degrees but the record highs range from the upper 80's to 101 degrees. The average relative humidity for the month is 72%. Statistically, rainfall averages .27 of an inch for the entire month. Good luck and have fun!

Aerial picture of Brickyard Cover Marine and Richmond Yacht Club