You're now free to shed the scarf and mittens. The Bay Area's cold snap is finally abating, with highs in the sixties expected this weekend.
How cold was it? Maybe not as cold as it seemed.
While San Jose managed to set a new low (by one degree) on Sunday, this hasn't been like, say, December of 1990, when Santa Rosa had consecutive lows of 21, 18 and 19. That one stands out in Jan Null's memory.
"This week we've seen temperatures, in the coldest places, down into the mid-to-upper 20s," said Null, a meteorologist who runs Golden Gate Weather Services. "We've sort of flip-flopped what we had for the month of December."
Since then, a high-pressure system has been parked over the eastern Pacific, and since air flows clockwise around high pressure, "It's arcing up through Alaska, down through British Columbia, and then coming right down the West Coast, so we're getting this relatively cold arctic air," Null explained as the last of the blast was moving through this week. That pattern is shifting, which will warm things up. And with the exception of mandarin oranges, which are super-sensitive to cold, citrus farmers in the Central Valley were not expecting widespread crop damage from this cold snap.
So why did this one seem so frigid? Earlier this week I overheard a colleague groan that this wasn't even like "Bay Area winter" but "real winter" (everything's relative: it was zero in my hometown of Syracuse, NY last weekend). Null says that people in the Bay Area are accustomed to some change in the weather about every three days. When any pattern lasts six days or more, as this one did, it begins to feel extreme. "People have short memories for weather," he says. And even when it warms into the 50s during the day, persistently frosty mornings reinforce the frigid factor, as morning temps influence how we dress for the day. The National Weather Service noted on Wednesday that, "every overnight low in Sacramento has been below normal this year."
Our refrigerator door is closing just as two federal science agencies called a media teleconference to affirm what they've pretty much said already: that 2012 clocked in as the warmest year on record for the contiguous 48 states. "It literally smashed the record," said Thomas Karl, who directs the National Climate Date Center in Asheville, NC. "We broke the record by more than one degree--that is quite impressive," he told reporters.
Scientists from NASA and the National Oceanic and Atmospheric Administration said Tuesday that globally, 2012 was the ninth warmest of any year since 1880 (when they started keeping records) and that, "With the exception of 1998, the nine warmest years in the 132-year record all have occurred since 2000, with 2010 and 2005 ranking as the hottest years on record."
When you look at it that way, maybe we shouldn't complain about a few chilly days.