It's summertime! Summer in the Bay Area has the conditions necessary to create strong, steady, reliable winds.
San Francisco Bay is known throughout the sailing world for its consistently strong summer winds. Photo by Joel Williams
By Captain Ray
Published: July, 2016
It’s summertime! Summer in the Bay Area has the conditions necessary to create strong, steady, reliable winds. Sailors wait all winter, knowing these winds will return with the coming of summer.
The central San Francisco Bay is known throughout the sailing world as one of the grandest of all places to sail. It is bounded on the south by the city front and Treasure Island and on the north by Angel Island and its lee. It extends west to east from the Golden Gate Bridge all the way across to the flats of Berkeley, a distance of eight nautical miles. Sailors often refer to this area as “the Slot” and the wind is consistently strong for six (and sometimes even seven or eight) months of the year.
This San Francisco Bay summer wind is the result of a unique geographical phenomenon. At 38˚ north of the Equator, the Bay Area is in the path of the prevailing westerlies. This means that most of the time the wind comes from the west. Just 60 miles inland from the Bay is the Great Central Valley, with its extremely high summer temperatures. From Bakersfield in the south to Redding in the north, afternoon summer temperatures often reach 100˚F and sometimes much higher. This is the only place on Earth that I know of where you can have a 50˚F temperature difference within 50 miles, without any elevation change. On a summer afternoon, it can be 55˚F in San Francisco and at the same time 105˚F in Fairfield.
As this very hot air rises, cooler air is pulled in to replace it. The hotter the afternoon temperature in the Central Valley, the more rapidly the heated air rises and the stronger the inward air flow. The Sierra Nevada, a 10,000 foot wall to the east, makes it unlikely that any replacement air will come from that direction. There are, however, many low places between the Central Valley and the Pacific Ocean through which this inrushing air can pass easily. Only the Golden Gate, however, goes all the way down to sea level. Because of this, the Gate is the funnel for the primary source of replacement air for the Central Valley. As this cooler replacement air squeezes through the Golden Gate, it is accelerated directly down the Slot, setting up the Bay’s exhilarating winds of summer.
I’ve just returned from a day of teaching sailing and the wind has been blowing hard once more. It’s been one of those days, 20-25 knots all afternoon! There will be a lot more of them as the summer season rolls along, but today was one of the first this year for me. I’ve been sailing on San Francisco Bay for over 20 years now, but the return of summer conditions always comes as a not-so-gentle reminder of why I sail here.
I’m physically tired and at the same time quite invigorated. The power of the wind is strangely energizing to my soul as, at the same time, draining to my body. My muscles ache a bit and I’ll sleep well tonight, but this vigorous dance with natural forces is refreshing to my spirit. When I’m on the water, the world ashore is a long way off, the phone doesn’t ring, and there are no emails that need a reply.
I’ve come back in off the water covered with a thin layer of salt spray. My glasses dotted with watery spots, face and hands wet. Some lines from a Jimmy Buffet song are going through my head: The salt air it ain’t thin / It sticks right to your skin / Makes you feel fine!
The rest of me is warm and dry, covered by my foulies. That’s an affectionate term sailors use for foul weather gear, the outer layer of waterproof protective clothing we all wear. As I pull off the gear, shake the water off it, and hang it up to dry, I think, “That was fun!”
Oh, yeah! It’s summertime!
Ray Wichmann is a US SAILING-certified Ocean Passagemaking Instructor, a US SAILING Master Instructor Trainer, and a member of US SAILING’s National Faculty. He holds a 100-Ton Master’s License, was a charter skipper in Hawai’i for 15 years, and has sailed on both coasts of the United States, in Mexico, the Caribbean and Greece. He is presently employed as the Master Instructor at OCSC Sailing in the Berkeley Marina.
