El Niño predicted, but likely to be weak
click image to zoomFigure 1. Global sea surface temperature departures as of May 1, 2014. The national Climate Prediction Center (CPC) recently posted an El Niño watch with the likelihood of El Niño development during the second half of this summer at 52%. The odds of development increase above 70% in the October-November period.
Of the 23 models used to project El Niño/La Niña events, only four indicate this event will reach moderate event criteria. The remaining 19 models indicate it will fall somewhere between a weak and weak-moderate event.
In general, the stronger projecting models develop El Niño conditions much quicker than weaker model projections. CPC has indicated that their forecast accuracy is weakest in the spring and strongest in the fall. The primary reason that CPC is issuing an El Niño alert during the weakest time of the year for forecast accuracy is the 100% agreement by various models that at least a weak event will materialize during the second half of 2014.
I have seen an exceptional amount of misinformation directed to the public in regard to this event and general El Niño trends. First, current weather patterns are not the result of El Niño conditions. Although the Equatorial Pacific has warmed dramatically over the past few months, El Niño conditions have yet to develop.
The recent movement toward a more aggressive precipitation pattern than we saw this past winter is the result of warming ocean conditions along the western U.S. allowing more energy from North Pacific ocean low pressure systems to sweep inland. During most of the winter, waters were cooler than normal and intensified the upper air ridge over the southwestern U.S. and allowed it to expand northward to the Gulf of Alaska. This in turn pushed weather systems into western Alaska and then down the eastern side of the ridge which brought Arctic air to most of the eastern United States.
Second, the primary impacts from El Niño events are felt from the fall through the spring in the Northern Hemisphere. Strong El Niño events usually begin their development in late spring or early summer. Not one of the 23 models used for El Niño forecasting indicates development before the end of July and none of the models anticipate a strong event will materialize.
Figure 1 shows sea surface temperature departures. You will notice that areas immediately north of the Equatorial Pacific are warmer than normal. South of the Equator, a large influx of colder than normal sea surface temperatures continues to be drawn in the Equatorial region from the western Antarctic region. This colder than normal conveyor belt that is limiting the early development of El Niño conditions is expected to continue slow development until at least the second half of this summer.
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