Once again it is winter on San Francisco Bay, and this winter season—at least until recently—has been a time for some very unusual and sometimes extraordinarily pleasant sailing. When there has been enough wind to actually sail, that is.
By CaptaIn Ray
Published: February, 2012
Once again it is winter on San Francisco Bay, and this winter season—at least until recently—has been a time for some very unusual and sometimes extraordinarily pleasant sailing. When there has been enough wind to actually sail, that is.
Winter sailing on the Bay is typically a light-air affair, punctuated by those winter storms that bring us very strong wind and rain. Through mid-January of this year the winter storms were completely absent. (If you’re a skier, I’m sure you noticed the lack of snow in the Sierra and were not all that happy about it!)
A very strong and very stubborn high pressure system had been dominating our weather. A high consists of a vast column of dense air, descending onto the surface of the earth, spreading out in all directions from its center and rotating clockwise (in the northern hemisphere) as it does. During the summer months, the center of this high is usually located out in the Pacific Ocean, somewhere between San Francisco and Hawai’i. The high’s southern outflow creates the northeast trade winds for the Hawaiian Islands; its northern outflow creates our prevailing westerly winds. This northern outflow also deflects the jet stream to the north, protecting the Bay Area from the storms generated in the higher northern latitudes.
Each winter season, as the sun crosses the sky lower and lower, the center of the high weakens and follows the sun south—but not this year! This year the high expanded significantly and actually moved north and east instead of shrinking and moving south. It then shifted the jet stream significantly to the north; hence, no winter storms.
In early January, the high sat over us and, because we were no longer in the path of the northern outflow, the winds became light or stopped completely. The air warmed as it descended on us; clouds evaporated and left us with unseasonably warm temperatures and clear, beautiful robin’s egg blue skies. Not bad for the middle of winter—unless of course, as I said, you are a skier. But even if you don’t ski, there is another downside to these conditions that affects all of us: The lack of wind results in the poor air quality we experienced in December and January, and an unusually high number of Spare the Air days.
Many meteorologists attribute all of this to La Niña, a cooling of the surface waters of the tropical eastern Pacific Ocean. This naturally occurring cyclical phenomenon is the counterpoint of the more widely known El Niño, a period when the surface waters of the eastern Pacific Ocean are unusually warm. The Spanish called this warm water phenomenon El Niño meaning "the child," a reference to the Christ child, because it was first observed during the Christmas period.
But this season is far from over and there is still plenty of time for rain. Long-term forecasts hint that La Niña is weakening, which may cause this unusual pattern to break down. In late January, storms had cleared the air and brought rain to the Bay Area as well as much-awaited snow in the Sierra.
Ray Wichmann, is a US SAILING-certified Ocean Passagemaking Instructor, a US SAILING 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.
