RAIN WILL RETURN. PROMISING TRENDS FOR LATE FEBRUARY AND MARCH.

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The dry forecast will continue for the next two weeks. After that there is increasing evidence that a pattern change may bring rain back to Northern California and the North Bay.

For now, high pressure will build bac across the entire West, keeping us dry, with a warming trend through the weekend. (Image 1) By Sunday the 13th, not much change as the high stays in place. (Image 2) Essentially no rain possibilities through the period. (Image 3)

Beginning in the 3rd week of February, models show the stubborn high pressure ridge finally pulling west. Still too close to the coast however for big storms to move in. (Image 4)

However, around 15-20 days out, the change continues. Low pressure begins to nudge in, as the high pulls further west. (Image 5) And the GFS ensemble outlook hints at a possibility of the first showers arriving shortly after. (Image 6) Probably nothing big, just the start of a pattern change for California.

Further out, more promising signs. The MJO (Madden Julian Oscillation) after being stuck for a month, shows signs of re emerging in the Indian Ocean….good for us. (Image 7)

This zone is associated with the displacement of high pressure off the West Coast with troughing…and it appears the long range forecasts have picked up that signal. Here is the weather associated with the MJO phases. (Image 8) As you can see, phase 3 (Indian Ocean activity) can be positive for rain along the West Coast.

The models suggest we return to normal rain in the last week of February, and even above normal to start March. (Image 9)

The GFS extended ensemble outlook supports a West Coast trough into mid March (Image 10), as does the European long range outlook. (Image 11)

So, plenty of reason for hope! As we’ve reported, long winter dry spells are not uncommon for California, we’ve had several lasting from 4-6 weeks over the past 20 years. This is San Francisco (Image 12)