Several of you have asked about the ocean surface temperatures this year, so this blog will explore that issue.
Let's start with the current sea surface temperature (SST) over the northeast Pacific (below).
Cool surface water along the West Coast is due to the upwelling (upward motion) of cold water from below. Cool water is also found to the north over the Gulf of Alaska. You have to go south of Baja California to get the really warm stuff.
How unusual are these sea surface temperatures? The next plot shows the difference from normal for this time of the year....also known as the anomaly.
Temperatures are actually a bit (about 1-1.5C) warmer than normal along the West Coast.
But cooler than normal in the Gulf of Alaska.
The sea surface temperatures are changing rapidly now due to the revving up of storm systems in the Gulf of Alaska, which are stirring the water in the vertical, bringing cooler water to the surface.
This is an example of the kind of storm action (from Sept 27) that is doing the mixing.
Consider the changes in the SST over the past week (below).
Wow. In some locations, temperatures have cooled by more than 2.5C (4.5 F) in that short time. On the other hand, some warming along the West Coast.
Why coastal warming along the coast? Because low centers in the Gulf of Alaska weaken the northerly (from the north) winds along the West Coast, which reduces the upwelling of cool water from below.
Expect more offshore ocean cooling during the next few weeks as air temperatures cool and the storminess increases.
Talking of cooling, there should be substantial cooling over the tropical Pacific as a moderate La Niña develops.
Meteorologists often look at a special zone in the central tropic Pacific (the Nino 3.4 area) (see below)
This area is now cooler than normal (blue colors in the figure below)
And the latest NOAA forecasts are for the cooling to strengthen.
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