Friday, June 12, 2015

El Niño Likely for the 2015-16 Winter

The National Weather Service Climate Prediction Center issued their latest El Niño/Southern Oscillation (ENSO) Diagnostic Discussion yesterday went mostly (but not quite all) in for El Niño to reign for the rest of the year and through the 2015-16 winter.
There is a greater than 90% chance that El Niño will continue through Northern Hemisphere fall 2015, and around an 85% chance it will last through the 2015-16 winter. - NOAA/NWS/CPC ENSO Diagnostic Discussion, 11 June 2015
An ongoing and strengthening El Niño is already in place over the equatorial Pacific Ocean.  Anomalously warm sea surface temperatures extend from the coast of South America across the Pacific to the dateline.
Source: CPC
Most of the climate models call for El Niño to strengthen over the next few months.  The plot below shows their projected sea surface temperature anomalies in the tropical Pacific from 120–150W and most are calling for strenthening anomalies through the fall, persisting into winter.  Some are calling for a strong El Niño., although there are a few that go for moderate to weak.

Source: CPC
All of this sounds exciting, but for the central Wasatch, there's very little correlation between El Niño and snowfall.  The graph below shows the relationship between 3-month snowfall and an index of El Niño/La Niña strength.  Nothing really to bank on here.

Three month (NDJ, DJF, JFM, FMA) accumulated snowfall at Alta–Guard vs. the corresponding ONI (labeled ENSO index). 
Courtesy Jeff Massey.
For the southwest, however, El Niño loads the dice for a wetter than normal winter, for the northwest, warmer than normal (and drier in the interior, but not necessarily the Cascades, although the warm temps often cause problems there for snowfall at temperature sensitive elevations during El Niño due to a greater fraction of precipitation falling as rain), as reflected in the seasonal outlooks produced by the CPC for Dec–Feb.

Source: CPC
Source: CPC
Personally, I hope a strong El Niño comes through.  The southwest could use some action and an active southern branch of the jet will give me some new blogging material next winter.

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