There are these things called "Atmospheric rivers." They are big long things up in the air that are loaded with water vapor, and much of the rain and other precipitation we experience comes out of them. This is notable when one of these rivers is extra wet, and there is an extra wet one out West in the US.
The Sierra Nevada range will be accumulating something like 16-20 inches of rain, but where that translates into snow, it will be up there in the 12 foot range, maybe more. There will be a very significant risk of flash flooding north of Sacremento and places in northern California and Oregon are going to get very very wet. The Bay Area will see lots of rain but mostly to the north, in Marin County.
A significant rainfall event is underway across portions of the West Coast as unrelenting Pacific moisture slams into the region. Northern California and southern Oregon will see the greatest rainfall totals of 10 to 20 inches by early next week. Strong winds and mountain snow will also impact the area.
The reason I mention this at all (those of you who live there, I'm sure, are totally up on this) is the following: This sort of excess rain is exactly what we expect to see more often because of global warming. This is the effect that global warming has on the hydrological cycle. It fills the Atmospheric Rivers with more moisture than would otherwise develop in them.
Recall that the worst flood in Ca history happened in 1861-1862, when the capitol had to be moved to San Francisco for a bit, and there were lakes in the Mohave Desert.
Our historical record in Ca really goes back not much more than 160 or so years, so for rare events we don't have a good idea of repeat periods. (Just like with earthquakes there).
I'm in the middle of it right now in Sonoma County. And after the past few years of less than impressive precipitation this "pineapple express" is welcome. Better late than never.
Anthropogenic global warming is a scientific fact. However, that is a climate issue. The periodic arrival of the "pineapple express" is really just weather, and some welcome weather at that.
Jeffrey, this storm system is not like Sandy ... It is something that causally happens normally. But this storm system does not lack a component of energy that comes from the release of fossil carbon into the atmosphere. These storm systems are either more common or wetter, and indespersed with more dry, because of global warming. Also, you're not getting the worst of it where you are.
Stay dry! Or at least dryish....
Lots of snow in the Sierras is a good thing for California: as with most places in the western US, their winter snowpack becomes their summer water supply. There are reservoirs to help damp out (no pun intended) the effects of a single dry year like last year, but a prolonged drought in the region would be bad news for everyone involved.
Snow in the Sierras is good. But I'm reserving comment on the effects of this particular storm until after it is over.
In mid-October I noticed unusually large numbers of pine siskins at my bird feeder. Over the years I've only recorded large numbers of this goldfinch species in autumns followed by a high rain winter. In fact, in recent years they have been completely absent.
Pine siskins are known as an irruptive species and seem, and I stress seem, to portend a wet or cold winter. My observations are truly anecdotal, and the sample size is small, but my bird feeder crystal ball couldn't be wrong....could it?
GOES whole disk, west, visible (i.e. a satellite view of the Pacific) is published online every hour. It would seem that a long band of clouds starts off the Columbian coast and streams nearly horizontal to a location northwest of Hawaii where it is turned (?) nearly 180 degrees by the jet stream to collide with my backyard in Humboldt County. I'm wondering if this is indeed the mechanism that loads the AR-storm with moisture, or just a coincidence of clouds and the Coriolis effect? Minor note: an AR-storm is not the same as the 1860s storm that flooded Sacramento; that was an "ARk Storm," a once-in-a-thousand-years version of an AR-storm. NASA has write-ups on both.
Or, is this actually a manifestation of the ENSO, El Nino Southern Oscillation?