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Winter El Niño usually brings tornado outbreaks, increased rain

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By NEIL JOHNSON | The Tampa Tribune

Published: November 5, 2009

Warm water spreading across the tropical Pacific Ocean has already provided a major benefit for Florida by blunting the hurricane season.

As water temperatures from the coast of Central America to New Zealand rose above normal, shifts in winds seven miles or so above the ground created conditions this summer that made it difficult for hurricanes to form in the Atlantic Ocean.

During the winter and spring, though, an El Niño impact on Florida may not be as beneficial.
A winter with an El Niño usually means a winter with tornadoes.

Three of Florida's five most deadly tornado outbreaks since 1950 happened during an El Niño. Those outbreaks in 1966, 1998 and 2007 killed more than 80 people.

During an El Niño in 2002 and 2003, Florida had 26 tornadoes. In the following winter and spring, with temperatures in the Pacific at normal levels, there were eight.

Though an El Niño has little or no effect on many states, Florida is different, said Michelle L'Heureux, meteorologist with the Climate Prediction Center who tracks the El Niño's progress.

"Florida will likely be having impacts associated with an El Niño," she said.

Those impacts can include powerful tornadoes, along with increased winter rain.

An El Niño causes the jet stream that blows from west to east across the country to move farther south than a normal winter. That drift in the jet stream lets more winter storms and stronger ones reach the Florida peninsula, said Amy Godsey, deputy state meteorologist.

"It brings storm systems farther south," she said.

Also, as the jet stream shifts to move over the Gulf of Mexico, cold fronts encounter masses of moist air from the Gulf, creating conditions that can explode into tornadoes and powerful thunderstorms.

"We don't know when or where these storms will be. We know there is an increased frequency," she said.

During the strongest El Niño on record that occurred in the winter of 1997 and spring of 1998, there were 66 tornadoes in Florida.

One outbreak of six powerful twisters in February 1998 smashed into the Kissimmee area with winds of up to 200 mph and killed 42 people.

Even a weak El Niño such as the one in 2006-07 can produce deadly storms.

A swarm of tornadoes swept through Lake, Sumter and Volusia counties and killed 20 people on Feb. 2, 2007.

On a more positive side, an El Niño may also help West Central Florida make up for below normal rainfall that's lagged 30 inches below normal over the past two years.

Central Florida usually gets 8 to 12 inches of rain in the winter. During an El Niño that amount can jump to 11 to 14 inches. The total can be even higher.

The 1997-98 El Niño brought torrential rains. Two of the National Weather Service monthly records going back to 1896 were set during that El Niño.

So much rain fell that tannin washed out from rivers gave water in Tampa Bay a brownish tint.
Scientists don't expect this El Niño to be nearly as strong as the one in 1997-98.

"We're definitely not projecting anything at that level. That was a once-in-a-century event," L'Heureux said.

The current El Niño should peak in intensity between now and January but it won't disappear.

"That's not to say the impacts will go away right away," L'Heureux said.

Scientists at the Climate Prediction Center aren't sure how long this El Niño will last, though they expect it could linger as late as May, she said.

Reporter Neil Johnson can be reached at (813) 259-7731.

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