Thursday morning we left Eureka, and crossed the bar at the entrance to Humboldt Bay by 9:30. It was a beautiful, unusually warm morning, with sunshine softened by the marine air, a low swell, and very light wind from the south. We motored south, confident that we would make it around Cape Mendocino by early afternoon.
Just before noon, we saw the wind build from about five knots to gusts up to 25 - all in the span of fifteen minutes. The Captain took over the watch at noon, and within another fifteen minutes, we were plowing into building seas and winds gusting to 35. Our speed was reduced drastically, and we began to take salt spray over the bow. We quickly decided that these were not conditions for rounding notoriously nasty Cape Mendocino, and that we would return to Eureka. With the wind behind us, we were able to sail comfortably on the jib alone, and were back at the dock in Eureka by late afternoon.
Several other sailboats experienced the same odd winds, and also returned to Eureka. It happens that there is a NOAA forecasting office a very short walk from the marina where we all moored. On Friday morning, a group of skunked sailors marched over to NOAA, and had a chance to sit down with one of the forecasters in front of his semicircle of four computer screens. This cordial weatherman told us that we had experienced what is known as a "Stratus Surge", and he was able to bring up the string of satellite images for the hours when it formed and hit us the day before.
The image above is of a similar event - this one along the southern California coast - and shows the funny finger-like leading edge of the thick stratus clouds.