On land, we can usually afford to ignore the wind. It comes in and out of our chests without fail, it tears shirts from the clothesline, and that’s about it. Not so in a small sailboat on, say, San Francisco Bay, where the wind is your boss. You require it to get anywhere. Heavy winds test mettle; light winds, patience. And the wind’s strength dictates how much of your sail to raise—more in light airs to catch every gust, and less in higher winds, to avoid being overpowered.
Though the wind tries to sneak around invisibly, you don’t need fancy electronics to keep tabs on it. The water and the land are always giving it away—even your own skin is. A tickle on your face means a wind of around 4 knots (a knot is a nautical mile per hour, or about 1.15 regular miles per hour): it means you are crawling back to the dock with all sails raised, and dinner will be late. Kira Maixner, a freelance sailing instructor and keen local racer, advises looking for “the texture of the water”—first ripples, then wavelets. Cat’s-paws appear on the water at around 12 knots—a dark patch, ruffled by an invisible small animal’s dancing. In a dinghy, you chase those dark spots to go faster. When the wind above a cat’s-paw catches your sail, the boat heels over sharply, forcing you to lean out, for counterbalance. Scattered whitecaps form at 7 to 10 knots; consistent ones at 15. Depending on boat and sailor, these may signal a hard cap on excitement, time to go in—or that things are finally getting interesting.
Sailors quickly learn that land is the boss of the wind, forcing it around peninsulas and over hills, in usefully predictable patterns. Most summer days, winds from offshore blow furiously past the Golden Gate Bridge and into the Bay. (They are rushing toward the Central Valley, whose hot air rises daily, leaving a pressure gap that wants filling.) Sailors refer to the waters just east of the bridge as the Slot, a place not to get caught with too much sail up. At Hurricane Gulch, another notorious patch just off Sausalito where the wind screams down from the Marin Headlands, Maixner watches for fog billowing over the ridges of the land. “You can actually see where it’s going to be windier and where it will be lighter, just because you can see the fog pushing in between the hills.” If you’ve been traumatized in the Gulch, head for the back side of Angel Island, a reliable hidey-hole from the wind.
There’s a lovely old scale for assessing what you are seeing: the Beaufort wind scale. Cal Maritime cadets standing night watches on the 500-foot training ship Golden Bear, in the Carquinez Strait, still learn it in their first sea term. The 200-year-old Beaufort translates visible sea state—what the wind is doing to the water—into wind speed. Cadets use a government-issued flipbook of photographs to match “what we see outside, what the wind is actually doing, [to measurements of] the anemometer,” says Chief Mate Doug Nagy. In doing so, they begin to develop their wind intuition.
The scale was invented by Francis Beaufort, a meticulous record-keeper of a British naval officer, who sought a common, objective way to report wind speeds. His first draft translated wind in terms of how much sail a warship would need (less in stronger winds, just like on the dinghy), but later he hit on sea state as more universal, since not everyone was on a warship. Eventually, a land translation emerged, too: what wind does to smoke, dust, branches, umbrellas. “Those were their instruments,” says Jeff Cathers, the school director at Modern Sailing. “The trees, the ripples on ponds or the lakes or the ocean, the size of the swells.” Ripples mean Force 1 (light air, equivalent to 1–3 knots). When the sea heaps up and white foam blows off the waves in streaks, that’s Force 7 (near gale, 28–33 knots)—go someplace dry and warm. Mariners’ observations using the Beaufort have been “remarkably consistent over the past 140 years and form the basis of the climatology of the oceans,” writes Frank Singleton, a former UK Met Office observations director.
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People like to riff on the Beaufort. Force 3 (fresh breeze), in the 1962 The Art of Coarse Sailing: “Difficult to make tea underway.” Singleton reports once seeing Force 9 and above, on a Météo-France card, defined as “Les enfants moins de six ans volent” (“If children less than six years old fly”). Cathers says that as you get to know a place, you can “find your own little indicators”—make your own Beaufort. You note when a particular tree starts to sway, or when a mast whistles. Once, Cathers had tied his laundry to the lifelines, and “I lost all my underwear,” he says. Force 5, in other words: a fresh breeze.
Update, March 2: A reference to “offshore winds” blowing into the Bay was corrected to “winds from offshore,” as an offshore wind refers to wind blowing toward the shore.
