Sad News: No More BLOB

A lot of folks are interested in the BLOB, the colorfully named area of warm water that periodically appears over the northeast Pacific.  And there is major BLOB news.... it is gone.  Let me describe the sad news.

Starting the autumn, the BLOB was relatively weak.  To illustrate, here is the sea surface temperature anomaly (difference from normal) for the end of October--as much as 2-3C warmer than normal!  This was associated with an area of persistent high pressure over the northeast Pacific.

But compare that situation to two days ago.  The BLOB is essentially gone, with an area of cooler than normal water developing.  Only immediately along the coast is the water temperature slightly above normal.

What killed the BLOB?   Persistent storminess over the northeast Pacific, something that is no surprise to the storm-battered residents of the Pacific Northwest. 

Here is the proof: the anomaly of the mid-tropospheric (500 hPa) heights from normal for the last 30 days.  Blue and purple indicate lower than normal heights, which is associated with more and deeper low-pressure centers, which in turn cause strong winds.  A big area of lower heights (or equivalently pressure) was found over the NE Pacific.

The BLOB forms with persistent high pressure that is associated with weaker winds.  Weak winds do not mix the upper ocean as much as strong wind, thus bringing up less cool water from below.   Persistent low pressure, with higher winds, are good at mixing, thus reducing water temperatures.  That is what has been going on lately.  There is no reason to expect that the BLOB is a sign of global warming.

So during this holiday season, your pleasure in enjoying a few day break may be tempered, at least a little bit, by a touch of sadness about the passing of our our old friend, the BLOB.  For myself, I find solace knowing that the BLOB  is sleeping, knowing that it will surely awake and return one day.

from Cliff Mass Weather and Climate Blog http://bit.ly/2GDwY87