Where's the rain?

It's certainly been dry around the Bay Area for the past couple weeks.  As of this evening, San Francisco has only received about 57% of its average rainfall for the rainy season to date (since July 1).  The strong upper-level ridge that was offshore last week, and resulted in the strong offshore winds across California, has moved inland and has steering incoming Pacific storms well north into Canada.  Along with the dry weather, we've also had poorer air quality across northern California.  First, winds have been light, resulting in stagnation.  Second, the upper ridge overhead acts to trap pollutants near the surface.  And third, with the cold nights, many residents turn to their fireplaces for warmth - but this burning is a huge source of particulate matter and soot.  So on days like these, please try to avoid using your fireplaces if possible.

So where has the rain been?  Lately, and much of this year for that matter, many cities in the Ohio River Valley surrounding areas have been setting rainfall records.  A snowy winter last year was followed by a very wet spring, frequent summer thunderstorms, and now a very wet autumn.  Cleveland, Cincinnati, Louisville, and Philadelphia have all now set new records for yearly precipitation - breaking some records that had been standing for over a century.  The map of year-to-date precipitation shows parts of Kentucky, Ohio, Pennsylvania, and New York with over 20 inches of rain above normal, or 150 to 200% of normal.


In contrast, the southern Plains and Gulf Coast are running large precipitation deficits, which in tandem with strong winds and hot temperatures this summer, produced the major wildfires across Texas.

Back to the future, our weather pattern should slowly change over the weekend and more so next week as an upper-level trough finally approaches the West Coast.  We should see a few chances for showers around San Francisco, but no major storm system are in the foreseeable future.