El Nino is Strengthening

We have known for a while that the tropical Pacific was transitioning from a neutral situation (near normal surface and subsurface temperatures in the tropical central/eastern Pacific) to an El Nino (above normal tropical ocean temperatures).  But during the past month, the warming has revved up and we will be officially in an El Nino very soon.

And we care about this, because El Ninos tend to make it warmer than normal in the NW with less snow, with the effect stronger as the sea surface temperature warms. 

Lets  start by looking at the sea surface temperatures for some "official" areas of the tropical Pacific (see below  for areas)

The Nino 3.4 area is the most popular, so lets take a look at it.  A lot of warming the past month, going from neutral conditions ( within .5C of normal) to almost 1.2C above normal.  Should be considered El Nino now.

If we look below the surface and look at the upper ocean heat anomaly (difference from normal of water temperature in the upper 300 m of the ocean) in the tropical Pacific along the equator, it is clear that ocean has become substantially warmer than normal:

Examining the sea surface temperature anomalies in map form from yesterday (below) shows the warm water along the equator and remnant of the blob in the Gulf of Alaska.  The blob is not dead yet!

The latest El Nino predictions, based on a collection of forests, projects that we will be in El Nino this winter--with more than a 70% probability.

But how strong?....that will make all the difference.  There are several types of models that predict El Nino.  Dynamical models simulate the atmospheric and  oceans using the full physics of the system.  Statistical models are based on past relationships.   Both are shown below.  Most models agree that the temperatures in the Nino 3.4 area will warm and are going for a weak to moderate El Nino.

Regarding our winter weather, the correlation of El Nino with NW weather is very weak before January 1, so anything goes for the next two months.   But if the forecasts are correct and at least a moderate El Nino is in place, expect warmer than normal winter temperatures, lower mountain snowpack than normal and a lowered probability of lowland snow after the new year.



from Cliff Mass Weather and Climate Blog https://ift.tt/2yY6APN