WARMING THROUGH THE WEEKEND. SURGE OF TROPICAL MOISTURE INTO CALIFORNIA NEXT WEEK.

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SHORT TERM

Strong high pressure over the Southwest will flex westward over the next few days, giving us warmer temperatures from 90-100 in much of the North Bay.

You can see the marine layer compressing and being scoured away by north-northwest winds off the coast. (Image 1) Also a robust moisture feed is visible over the desert Southwest.

Beginning today, high pressure will push into California, and strengthen into the weekend. (Image 2) For us that means temperatures up to 10 degrees above normal, with continuing cool marine air near the coast. (Image 3) Saturday may be the warmest day with 90-100 degree inland temperatures. (Image 4)

NEXT WEEK

Monsoonal moisture from the Southwest will push into California next week. It’s still unknown how far north it will reach, but the Bay Area looks to be a rough dividing line at present. (Image 5) This is something to keep an eye on. For now we’re just expecting showers over the Sierra, and perhaps Southern California. (Image 6)

LATE MONTH HEAT?

There are early signs that late July may bring a substantial heatup. The pressure set up two weeks from now shows strong high pressure extending over California. (Image 7) And there are hints in the long range ensemble outlooks of hot temperatures over much of California during the last week of July (Image 8)

The good news is that despite heat ups and cool downs, the ensemble models continue to suggest that, on balance, the next month will bring near average temperatures (Image 9)

LA NINA – HANGING IN THERE

Our overall moderate summer may have lots to do with the current (continuing) La Nina conditions, a pattern that appears to be not only hanging with us, but strengthening. In both June and July, sea surface temperatures have been unusually cool in the tropical eastern Pacific. (Image 10) And that is almost certainly impacting our summer weather.

All signs are that we may be headed for a third straight La Nina winter, as current signals show sea surface water near the equator will continue to be quite cool (La Nina signal), a pattern that shows signs of holding on at least through the fall. (Image 11)

Too early to talk specifics, but as we know, La Nina typically puts the Bay Area right on the dividing line between wet and dry. (Image 12) There have been many La Nina winters of above average rain. In any case, long range outlooks show La Nina weakening as the winter goes on, with neutral or weak El Nino conditions possible by late winter.