Coastal Ocean Update

 Several folks have asked me about the coastal water temperatures, including whether the recent storms have had an impact.     So let's take a look!

If you plan to get into the water around here, you better pick up a wet suit, since sea surface temperatures (SSTs) are only in the upper 40s.

The map of current sea surface temperatures (sorry, in °C), shows the cold water along the Northwest Coast (the dark blue color is 9-11°C, 48-53F).   The California coast is not particularly warm. You really need to head down to southern Mexico to get pleasantly warm ocean temperatures.

What is even more interesting is whether the water temperatures are warmer or colder than normal and why.    

To show this, below is the SST difference from normal for October through December. Slightly warmer than normal near the coast, but cooler than normal (blue colors) offshore.  Much warmer than normal in a swath extending from Hawaii westward.

But why this pattern, with roughly equal areas of above and below normal temperatures?  

Could it be the result of the persistent weather pattern this fall with one strong cyclone after another moving northward a few hundred miles off our coast?

Let's check this out.

The next plot shows the difference of sea-level pressure from normal for October through December.   Unusual and persistent low pressure was found to our west.  In contrast, higher than normal pressure over Hawaii and westward.   The plot thickens!

Surface persistent pressure patterns influence the winds, which in turn affects sea surface temperatures.  As shown below, low pressure off the coast would tend to cause southerly winds near the Northwest coast (moving warmer water northward), westerly winds north of Hawaii (bringing in warmer water from the west), and northerly winds offshore (causing cooling).

 This is NOT the kind of wind field one normally sees with La Nina periods, by the way.

Was this Fall Wetter or Drier than Normal?

The answer:  most of the region has enjoyed near-normal or above-normal precipitation.

As a result, our region is going into the new year in pretty good shape regarding water.

Starting with snowpack, Oregon is crazy above normal and Washington is modestly above normal overall (see percentages as of today, below).  California is in good shape as well.

Meteorologists and water resource managers pay close attention to the precipitation starting October 1, the beginning of the "water year" and our wet season.  The figure below shows the difference from normal from October 1 through December 31.   Northern California, Oregon, and eastern Washington are all well above normal.  Most of western Washington is nearly normal, with a slightly below-normal area over the South Sound.

With such healthy precipitation totals, it is not surprising that river streamflow is in good shape (see below).  Most of Washington is near normal (light green), with several above-normal reports (blue dots).  Far more above-normal streamflow sites in Oregon.

It is interesting to look at some individual sites, plotting the cumulative precipitation against normal from October 1 to today. (from line shows the normal values) 

Quillayute, along the north coast, ended up well above normal.

Bellingham was a bit wetter than normal.

Seattle, rainshadowed by the Olympics this fall, was modestly drier than normal.

Olympia was nearly normal

And Portland was above normal.

Eastern Washington was very much wetter than normal this fall.  

Spokane ended up several inches above normal.

And the Tri-Cities and Ellensburg were quite wet as well.

Considering all this, it is surprising that the U.S. Drought Monitor graphics shows dry condition to moderate drought east of the Cascades (see below).   I am concerned about the Drought Monitor, which is popular with many media outlets.  

Finally, Seattle's water supply looks to be in excellent shape with reservoir levels slightly above normal.  You can drink to that.