As El Nino Peaks, Likelihood of La Nina Considered

By Brian K. Sullivan | October 15, 2015

Just because the weather-roiling El Nino in the Pacific Ocean is still months from peaking, it doesn’t mean it’s too early to talk about La Nina.

La Nina, sometimes thought of as El Nino’s opposite number, is a cooling of the equatorial Pacific and brings its own level of mayhem to world weather patterns. The National Oceanic and Atmospheric Administration considers the two of them “extreme phases of a naturally occurring cycle.”

While La Ninas can grow on their own, they have come out of the remains of an El Nino, according to the University Corporation for Atmospheric Research in Boulder, Colorado.

There is a “bounce-back” in the ocean that compensates for El Nino’s warmth, the way a pendulum swings.

That said, the probability of a La Nina after an El Nino aren’t exactly the same as sunshine arriving after a long, dark night. There ’s always a chance the morning will be cloudy, or there will be an eclipse.

“The chances of a La Nina following a big El Nino do go up,” Michelle L’Heureux, a researcher at the U.S. Climate Prediction Center, said in an interview Thursday. That doesn’t mean it is going to happen this time, she said.

Australian Bureau of Meteorology said Tuesday the present El Nino is the strongest since the record event of 1997 and will last through the end of the year, starting its decline in 2016.

No Prediction

As of now, the center in College Park, Maryland, isn’t calling for a La Nina close on the heels of the El Nino. The best forecast is for the ocean to return to a neutral state between its hot and cold extremes, after El Nino gradually weakens through the Northern Hemisphere spring.

In May to July, chances are better than 50 percent conditions will be neutral and greater than 30 percent an El Nino will still be going on, according to an outlook published Thursday by the climate center and the International Research Institute for Climate and Society at Columbia University’s Lamont Campus in Palisades, New York.

The chances of a La Nina are less than 10 percent in April- June and 16 percent in May-July.

So What?

So, what if a La Nina should show up ? What’s the worst that could happen?

A large part of the agricultural U.S. tends to dry out during La Nina events. The widespread Midwest drought three years ago came during cool conditions that began in late 2010 and persisted through the early spring of 2012.

There can be an increase in Atlantic hurricanes, because the wind shear that keeps their numbers down in El Nino years is often absent. Parts of Brazil, northern Australia and Indonesia can be wetter than normal.

In the climate center’s records, the El Nino of 1991-92 was followed by the Pacific returning mainly to its neutral state before warming again in 1994-1995.

The record El Nino of 1997-98 was followed by a La Nina, and the Pacific remained cooler than normal for years afterward.

In contrast, the La Nina of 2010-2011, after an El Nino, was followed by another La Nina a year later.

So as the current El Nino peaks, it might not be a bad idea to consider what could happen next year. However, L’Heureux said models used to forecast these events sometimes have trouble transitioning out of one state and into the next, so no one should believe the future is already foretold.

“Historically, when you look at it, it’s not a slam dunk,” L’Heureux said.

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