La Nina chances increase; that could be bad news for 2016 hurricane season

Global weather patterns are about to take a dramatic shift as the mighty El Nino finally shows signs of weakening, making way for an atmospheric slingshot that could bring on La Nina.

While El Nino acted as Florida’s bodyguard during last year’s hurricane season, knocking the heads off storms with powerful westerly winds aloft, La Nina is more reserved and just as likely to allow a cyclone to pass as not.

The chances that La Nina will appear by September were increased to 50 percent last week by the Climate Prediction Center. Hurricane season runs June through November.

“The higher the chances of La Nina, the higher the chances for a bigger than usual hurricane season,” said Bob Henson, a meteorologist and blogger for Weather Underground. “You have less wind shear and more favorable conditions for showers and thunderstorms to develop into hurricanes.”

During El Nino, water across the eastern path of the Pacific Ocean warms, making radical shifts to rainfall patterns. Showers are suppressed over Indonesia and moved to the eastern part of the Pacific. There strong thunderstorms form, which influence wind patterns in the upper atmosphere, reducing wind shear in the Pacific and increasing it in the Atlantic.

With La Nina, waters in the Pacific cool, rainfall retreats to the west, and the westerly winds wane.

“If 2016 transitions to La Nina, it will be a dramatic shift for the Atlantic hurricane season,” said Bill Patzert, a climatologist with NASA’s Jet Propulsion Laboratory in a December interview about El Nino. “It’s like a pendulum, a flip-flop, between El Nino and La Nina.”

In winter, La Nina means a drier weather pattern for Florida. During neutral years — between La Niña and El Niño — ocean temperatures, tropical rainfall patterns and wind patterns are closer to long term averages.

In an early discussion of how the 2016 Atlantic hurricane season will play out, Colorado State University researchers looked at storm seasons that followed the 10 strongest El Niño years since 1871.

Seven of the years were marked by more and stronger storms, including three — 1878, 1906, 1998 — that were very active.

According to the National Oceanic and Atmospheric Administration, 1998 was the deadliest hurricane season in more than 200 years with thousands of deaths reported in Central America.

“In a remarkable span of 35 days, starting on Aug. 19 and ending Sept. 23, 10 named tropical cyclones formed,” the National Hurricane Center notes in its archives about the 1998 storm season. “That’s about a whole season’s worth of activity crammed into a month.”

Six of the 1998 storms made a U.S. landfall, including Hurricane Earl, which hit near Panama City as a Category 1, and Mitch, a formidable Category 5 at one point, which made landfall near Naples as a tropical storm.

But Mike Halpert, deputy director of NOAA’s Climate Prediction Center, said the atmosphere may take some time to react to the temperature changes in the Pacific Ocean. While 1982 was an El Nino year, Halpert said La Nina didn’t come on strong until 1984.

The 1983 hurricane season was notable for having just four named storms. In 1984, there were 13 named storms.

“Some things we can model and understand but there is a lot of natural climate variability and we probably will never be able to understand everything,” Halpert said. “The question is how much of an impact La Nina will have on this hurricane season and that’s still a big question.”

Florida’s gone an unprecedented 10 years without a hurricane making landfall. 


Read more about how La Nina may impact hurricanes here. 



Reader Comments 0