Cold Water Along the West Coast and Unusually Cold Over Southern California

 If you want sun and warmth, don't travel to southern California during the next week.   

Stay in the sunny Pacific Northwest, where the weather will be as close to perfect as one might imagine.

Much colder than normal water is found off the West Coast from Oregon to Baja, and southern California is cold and enshrouded with clouds (see visible satellite image a day ago).  June Gloom+

Sea Surface Temperatures

Here is the latest plot of sea surface temperatures along the West Coast, with large stretches below 50F (purple colors, below 10C).  Too cold to swim in!

Much of the offshore waters are well below normal, as indicated by the blue colors below.

Why are the coastal waters so cool?   Probably, two reasons.

First, there have been persistent, unseasonable low-pressure areas that have repeatedly formed off southern California.  

To illustrate,  the upper-level heights at 500 hPa (think pressure around 18,000 ft) this morning are shown below.  A low with a nice counterclockwise circulation is just offshore of southern California.  Such lows are associated with stronger winds and atmospheric disturbances that stir up the upper ocean, mixing cooler water from below up to the surface.

And then there have been periods when high-pressure builds offshore and northerly winds develop over the waters of northern CA and Oregon.  This pattern results in coastal upwelling of cold water within 100 miles or so from the coast (see a schematic of coastal upwelling below).

Unfortunately for the chilled residents of coastal California, powerful northerly winds will develop offshore this week as a strong high-pressure area builds over the northeast Pacific (see forecast pressure and winds for Sunday).

It will be like putting a refrigerator element along the West Coast!

San Diego and LA Chill

    To understand how bad it has been, take a look at the observed temperatures at San Diego (blue bars showing daily highs and lows), compared to the normal range (brown band),  Record highs and lows are also shown.  

All days but two did not reach the normal highs.  The lows on most days dropped below the normal lows.  NO heatwaves.

And the frigid situation (with rain by the way) is not ending.  Below is the latest extended temperature prediction for Los Angeles Airport.  Not a single day above the mid-60s.  Boring and cold.

For the same period, Seattle will be basking in temperatures from the 80s to the mid-70s, with enough variability to make it interesting.

I suspect you will see the front page of the Seattle Chamber of Commerce website reflect the new weather realities:

  Note: this is not an actual page, but a fanciful simulation of one.