Monday, December 1, 2014

Northwest Cold Wave is California's Salvation

When sustained cold air moves into the Northwest, the frontal zone separating cold and warm air shift southward into California.   The temperature difference between the two air masses is associated with the jet stream, so it usually heads south at the same time.  Fronts bring clouds and rain.  So does the jet stream.   In short, with cold air dominating the Pacific Northwest, the frontal weather action and jet stream related storms head to California.

OUR clouds and precipitation are being sent down to those poor folks in drought-plagued California.  They desperately need the precipitation.  And we need the late fall sun.

Let's take a look at this grand exchange, by starting with the visible satellite image this afternoon.
Pretty much clear in Oregon and Washington, but California is enshrouded.  Good to see.

The 7 PM Sunday surface chart shows the situation.  High pressure over us and a frontal band bisecting California.

 The 24h rainfall totals ending Sunday at 9 PM show the respectable totals around much of the Golden State. Over 1.5 inches near the coastal mountain SW of San Francisco and .5 -1 inches over much of California's mid-section...the most extensive rain they have had since last year.

Here is the storm total (last two days) from the San Francisco radar--lots of areas got 1-2 inches!

Californian's are seeing something there are not used to:  rainbows.  Perhaps a sign from providence that their suffering is ending.

And yes, the weather gods seem to be taking a liking to CA folks.  Let's take a look at some upper-level (500 hPa) maps, starting with Tuesday evening.  A closed low off CA, with strong flow (lines close together) heading into central and southern CA.
4 AM Friday?  A trough offshore and moist southwesterly flow heading into CA.  You can bet on precipitaton.
 The WRF model precipitiation forecast for the next two 72h periods shows California getting moisture, with nothing over Washington State for the first 3 days.

They need a lot more than this, but a good start. This is an weak to moderate El Nino year, and El Nino years (particularly strong ones) bring enhanced rainfall to southern CA.  The latest NWS Climate Prediction Center 3-month precipitation forecast is going with that idea.

This event is literally a drop in the proverbial bucket for California, but it is a welcome first step, considering the historic drought hitting that state.


JewelyaZ said...

This is GREAT news, Cliff! I don't mind being dry when we're cold -- lowland snow does not thrill me at all beyond the first ten minutes of "kids' flakes" -- and California needs a great deal of precipitation to catch up. We've already had a wet fall, right? November was slightly below average for Bellevue (4.25" vs. 5.19") but I think October was well ahead of average, 6.75" instead of ~3.2". California can take it!

JGD said...

Hey Cliff - I've had a question for you that I've been wondering for a while: how do you think climate change will affect the Pacific Northwest? I know there are a ton of unknown's at the moment regarding this area, but what do you think?

JordanP said...

Cliff has covered this very well a couple of times in the past. Just look through his past postings to get an idea.

Here was a good one from a while ago.

BJ said...