Can El Nino be good for the United States?

The abnormally warm Pacific Ocean water symbolizes El Nino  (Source: NOAA)

As you’ve heard, El Nino has returned in the Pacific Ocean (off the west coast of Mexico).  An episode of El Nino has global repercussions on the weather.  Climate scientists with NOAA have said this El Nino is among the strongest on record – on par with the last two major El Nino events that came in 1982-1983 and 1997-1998.  They also say there’s a “95% chance that El Nino will continue through the Northern Hemisphere winter 2015-2016.”  

There are two branches of the jet stream that affect weather in the United States.  The northern or “polar” branch helps regulate cold air, while the southern or “subtropical” branch helps regulate milder air.  During an El Nino event, the southern branch of the jet stream moves farther north in the United States.  That’s good news for much of the western United States, since that would help guide more storms into drought stricken areas of the west coast. 

The 1997-1998 El Nino event contributed to an exceptionally wet winter along the altered track of the subtropical jet stream.  For example, the state of California had its wettest and Florida had its second wettest February on record in 1998.  Most of California and Nevada are currently experiencing extreme drought conditions, so they would welcome appreciable rain and snow.  Mountain snow is especially important out west because it helps replenish the water supply as it melts.  However, if too much rain falls too quickly, then flooding and mudslides would ensue.

El Nino also leads to more unfavorable conditions in the tropical Atlantic as wind shear (winds that change speeds with altitude) tends to be higher and sea surface temperatures trend cooler.  Such was the case during both the 1982-1983 and 1997-1998 El Nino events.  The National Hurricane Center says an average hurricane season in the Atlantic Ocean features approximately 11 named tropical storms, with 6 hurricanes of which 2 or 3 become “major” hurricanes.  However, in 1982 there were only 6 tropical storms, 2 hurricanes and 1 major hurricane, while in 1983 there were 4 tropical storms, 3 hurricanes and 1 major.  There also was another quiet Atlantic hurricane season in 1997 largely due to El Nino. 

So far, the 2015 season has been relatively benign with only 8 tropical storms and just 2 hurricanes and 1 major hurricane.  While El Nino affects weather patterns globally, all of the repercussions aren’t bad.  I will describe any effects that an El Nino event has on the Mid-Atlantic Region in a future column.