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El Nino, La Nina and this year's storm season

Posted at 3:08 PM, May 12, 2016
and last updated 2016-05-12 21:40:17-04

Hurricane seasons are notoriously difficult to predict.

Experts at Colorado State forecast a near average hurricane season, which would be more active than what we saw last year.

Here are some factors behind the pre-season forecast.

Last year there was a strong El Niño which suppresses hurricane activity in the Atlantic by enhancing wind shear and preventing storms from developing.

In fact, in the Caribbean where the shear was strongest, we only had one storm move in and quickly die out. 

This year, global forecast models are predicting not only for the El Niño to die out, but for a complete reversal to a La Niña by the middle of the hurricane season.  In a La Niña the Pacific Ocean water near the equator is cooler than normal.

This usually means a decrease in wind shear, which in turn increases the potential for tropical activity.

However, there are opposing signals at work this season. The North Atlantic water temperatures are a lot cooler than normal right now, and although hurricanes don't enter this region,  years when there's cooler water south of Greenland there are less frequent and intense hurricanes overall.

So that may cancel out a more active year that a La Niña would normally bring.

Colorado State University notes there's still plenty of uncertainty with the forecast, because the La Niña hasn't even formed yet, and the Atlantic water temperature may change by the middle of the summer.

NOAA’s seasonal forecast is due May 27th and CSU will have an update in early June.