A Flash in the Pan
Photo essay: the vineyard's new green winter coat

Enjoying the "Atmospheric River" of Moisture

It's wet out at the vineyard. So far today, we've received over an inch and a quarter of rain, with the heaviest, according to radar, still to come.  This is the fifth day in a row we've received significant rainfall, more than five inches overall. This is all a result of what the National Weather Service has been calling an "atmospheric river" of moisture"; essentially a supercharged plume of moist air that stretches across the Pacific, flowing east from its roots near Hawaii all the way to its mouth in northern California.  There's a great graphic that shows the concentrated moisture on the content-rich and well written weather blog The Weather Guru:

Atmospheric river

Our winter weather cycle features brief, intense periods of wet weather broken by longer dry interludes.  It's rare that we get more than a couple of wet days in a row.  But when we do get an exteneded period like this, we can get a quarter or more of our total expected winter rainfall in a few days.  It looks like this will be the case for the wine regions a little to our north; many locations in Sonoma have tallied 15 inches or more over the last week.  But whatever we end up at, be it six, seven or eight inches, we're still happy to have such a good head start on our winter rain.  

I often use a simple measurement to tell where we are.  We average between 25 and 30 inches of rain a year.  This rain comes in half the year, November through April, a period covering 26 weeks.  Although the moisture isn't evenly distributed over those 26 weeks (it's wettest December-February) I often compare the rain we've received to the number of weeks we are into our rainy season. With this rain, we're in our fifth week and have accumulated 6.5 inches of rain.  So, we're ahead of pace, with our wettest season still to come.