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Understanding How El Niño Affects Hurricane Season


We’re two months into Hurricane season, and so far, it’s been a pretty quiet one. That’s due, in part, to 2015 being an El Nino year. 

To understand why, look just off the west coast of South America at the Southern Pacific Ocean, right around the equator. “When that region becomes warmer than normal, we call it El Nino. The anticipation is that it’ll get stronger as summer goes on," says Barry Keim, Louisiana's State Climatologist. 

Specifically, he says, El Nino is higher than normal sea surface temperatures in the Pacific. Sea surface temperatures in the Atlantic have the most effect in Louisiana’s hurricane season. 

El Nino happens every few years. And when it does, it brings with it teleconnections, unusual weather events that pop up all around the globe, even here in Louisiana. Keim explains that “one of those relative to us is that it creates lots of wind shear over the Atlantic Ocean.”

Wind shear is the upper level wind speed and direction, and like the jet stream, moves generally west to east. It acts like a giant fan blowing off the top of a hurricane, keeping it weaker by not allowing it to vent in the upper levels. “It tends to mitigate the formation of storms. And the ones that do ultimately form tend to be weaker if it’s encountering some wind shear," says Keim.

Now that doesn’t necessarily mean we’re in the clear. El Nino occurred back in 1992, a year often remembered here in Louisiana for Hurricane Andrew, one of only three Category 5 storms to ever make landfall in the US.

“It doesn’t mean you won’t get hit," warns Keim, "but that you’re chances of getting hit are going to be somewhat lower than an average season.”