A Junior Blob Off the West Coast--But Still Cool for a Hurricane

The latest plot of the difference of the current sea surface temperature from normal (the SST anomaly) available from NOAA shows that some of the most unusually warm water across the planet is now offshore of the West Coast.   Some of the water is 2.5-4 C degrees warmer than normal (4.5-7.2F warmer than normal).  Since it has only been there a few months, let's call it a junior BLOB.

One reason for the BLOB development has been a persistent areas of high pressure over the eastern Pacific.

Some folks have asked me whether we might get a hurricane like Dorian over the West Coast, particularly since our offshore waters are warming.  A good question.

The answer is no.  Even with a major BLOB off our coast, the sea surface temperatures over the eastern Pacific are still too cold.   Hurricane development requires ocean temperatures of at least 80F (or 26.5F). 

Below is the latest plot of sea surface temperatures around North America provided by NOAA.  Blue/Green is cold.   Red is warm (you could guess that!).  26.5C or 80F is where the color turns from yellow to orange.    The Gulf of Mexico is great for hurricanes, as is the south Atlantic.

But yikes!  The water temperatures off the West Coast even with Ms. Junior BLOB is WAY too cold (around 50F).  No hurricanes for us.   Ever.

If you look carefully at the first picture above, you will notice some blue color off of southern Florida....that is the result of the churning of the upper ocean by Hurricane Dorian, bringing up cold water from below.

To really see this effect, let me show you the sea surface temperatures measured at a buoy that was run over by the storm (buoy 41010, just north of the Bahamas).  Pretty amazing... a cooling from around 85.5 F to 81.3 F.

This cooling of the ocean's surface was enhanced by the halting of the storm's motion over the Bahamas (so the storm was stuck over cooling water), and led to the storm weakening rapidly from a category 5 to a category 2 storm.

Announcement:  I will be giving a talk "The Great Storms of the Pacific Coast" in Ocean Shores at 6:30 PM on September 7th at the Shilo Inn as part of the Coastal Interpretative Center's summer lecture series.  More information is found here: https://www.interpretivecenter.org/.   Shilo Inn is offering special room rates for those wishing to stay overnight, as well as a special buffet.