On the Watch for El Nino

2:53 PM, Dec 6, 2012   |    comments
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The National Oceanographic and Atmospheric Administration (NOAA) is keeping a close eye on the waters off the coast of Ecuador, in the southern hemisphere of the Pacific Ocean. This is the area where the ENSO, or El Nino Southern Oscillation, takes place (pictured below). You've probably heard of El Nino or La Nina, which both result from the ENSO. But what is it?

This map of the Pacific Ocean is from the NWS's ENSO Site.


The "O" is the key part of this acronym- oscillation. The ocean temperature here is always changing, but what scientists are looking for is an unusually warm or unusually cold trend in this water. If the temperature is consistently more than 0.5 degrees Celsius above normal, for a few months in a row, then an El Nino condition is occurring. La Nina is the opposite condition, in which the water is cooler than normal. So, the term "El Nino" is not directly referring to a storm; instead, the label is given to a time period when the ocean water is in an anomaly (unusually warm or cold temperature) for a length of time. Of course, the bigger the temperature difference is, and the longer it lasts, the stronger you can expect the El Nino or La Nina event to be.

You've probably heard a lot about the impacts of an El Nino condition on the news, especially in the recent past. The El Nino of 1997-1998, for example, has been blamed for record flooding and the resultant mudslides in southern California. El Nino summers are also thought to produce more tropical storms, though the impacts of El Nino are generally stronger in the winter than the summer in North America.

Why does it matter to us? Because even though the strongest impacts from El Nino are generally concentrated in other parts of the country (namely, the southern tier of the United States), they can produce a domino effect of weather pattern shifts, and these climatic dominoes can fall all the way to the DC Metro area and beyond. A good example was in the record-breaking winter of 2009-2010. Even though El Nino conditions are known to produce slightly warmer conditions in our region, they are also notorious for producing more coastal storms, like the back-to-back blizzards in December 2009 and the nasty Nor'Easter of March 2010. ?

The above image shows the temperature anomalies, or differences, from normal ocean temperature at their most recently updated reading. (Courtesy NOAA.gov)

The NOAA commission studying ENSO has noticed a warming trend in the equatorial Pacific since June of this year. Even though we are "ENSO Neutral" right now, which means we are not in El Nino or La Nina, the forecast calls for temperatures in that region to remain slightly above normal. So we can conclude that if an El Nino winter is on the way, we could see an increase in the number of coastal storms during that season... and maybe even an above-average snowfall season. Stay tuned!

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