Ominous Changes Behind Bay Area Heat Wave

by Val Germann

Mark Twain once said that the coldest winter he ever spent “was a summer in San Francisco.” And it’s true that summers in the City by the Bay can be cool, even cold, thanks to rising air inland and the chilly Humbolt Current just offshore. But something changed this summer as this quote, from the San Francisco CHRONICLE, outlines:

The Great Heat Wave of 2006 was not just an epic meteorological event — it was an epochal one, unprecedented in the north state’s weather annals, meteorologists agree.

Yes, it was bad, very bad, and the closer you look at it the worse the overall situation seems. First, of course, it was hot in the afternoon, for days on end, something that just does not happen in that part of the country:

It has been hotter for longer than ever before, and the weather patterns that caused the scorching temperatures were positively freakish.

Temperatures in the Bay Area broke 110 degrees in more locations and for a longer time than ever before, by far. But it wasn’t just the daytime heat, it was more:

Additionally, the Bay Area was visited by something truly alien during this hot spell: huge quantities of moisture from the Gulf of Mexico and Gulf of California. An anomalous high-pressure flow swept humid air from those areas into Northern California. There the high pressure remained stationary, Newmerzhycky said.

What this air mass did was make San Francisco more like St. Louis or Atlanta at night, brutally hot.

“It stayed so long the humidity penetrated to ground level,” he said. “That contributed to the triple-digit daytime temperatures and prevented the nighttime cooling you typically see.”

Air conditioning is a rarity in the Bay Area, now. But if this kind of weather continues it won’t be rare much longer. And weather this hot may be the future because something may be happening to the water just offshore, in that Humbolt Current, originating in Antarctica:

But offshore water temperatures recently have been 2 to 4 degrees above normal, Newmerzhycky said. “That temperature difference could be preventing the thermal barrier that’s required to usher cool marine air into the Central Valley,” he said.

Regulars here at Star Phoenix Base will know what this could mean, that the rapidly warming Arctic and Antarctic may be leading to a weakening of currents like the Humbolt that distribute solar energy around the globe, warming Europe in the winter and cooling San Francisco in the summer.

Let’s hope that these conditions are in fact “freakish” and not soon to recur. But hope may be all we have.

Read the entire CHRONICLE article here.

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About Val

I am a long-time teacher of science and astronomy with a strong interest in resource conservation and the environment.
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