Cliff Mass Weather Blog: El Nino Weather Ahead

We are in a very strong El Nino and typically its influence on Northern Hemisphere weather circulation increases during December, with the most profound impacts after January 1.

We will get a potent taste of a typical El Nino pattern next week.   

Let me show you.

As I noted in a previous blog, the sea surface temperature of the tropical Pacific has become far warmer than normal (see below).  In fact, the critical El Nino index (region 3.4 sea surface temperatures anomaly from normal) is now about 2°C above normal, resulting in a strong El Nino.

The difference in temperature from normal.

El Ninos tend to produce a certain atmospheric pattern over the eastern Pacific (see below), with a portion of the Pacific Jet Stream heading into California, bringing wetter-than-normal conditions over central and southern California.  In addition, low pressure develops offshore of the West Coast, and warmer than normal temperatures are observed over the western U.S., particularly across the upper plains.

 And a very similar pattern is predicted next week.

The predicted upper-level map (300 hPa pressure level, about 30000 ft)  for Wednesday shows heights (solid lines) and winds (shading), indicating a jet stream (strong winds in knots, reds and orange colors strongest) entering southern California and a low offshore.

The impact on western U.S. precipitation will be profound.  As shown by the cumulative precipitation through next Friday,  California will be far wetter than Oregon and Washington, with San Diego and LA getting 2-3 inches.

The latest NOAA/National Weather Service  6-10 day precipitation outlook predicts drier than normal conditions for the Northwest, but very wet over the southwest. 

Classic El Nino.

Also classic is the very warm conditions prediction for the western U.S., particularly the upper plains.

So those heading south for the holiday season are well advised to take their raincoats and umbrellas.  Northwest weather will move to the Southwest for a while.


I will have a special Zoom session for Patreon supporters this Saturday, December 16 at 10 AM.


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