tampabay.com

Is El Nino toying with us?

The handy hurricane blocker could bring rain — lots of it — later on this winter.

By GRAHAM BRINK
Published October 16, 2006


El Nino, the phenomenon that helped thwart hurricanes this season, could bring lots of rain to Central Florida in the coming months.

Forecasters expect the latest version to be weak to moderate. Weak, and we might not notice the difference. Moderate could mean flooding in some unlucky areas.

El Nino, which traditionally peaks from December to April, is often a good news-bad news event.

It ends droughts and snuffs out wildfires. But it also stirs up severe winter storms and exacerbates famines, and it played a role in collapsing one of the world’s largest fisheries.

“Sometimes it’s helpful. Other times it” floods people out of their homes, said Ernie Jillson, a meteorologist at the National Weather Service in Ruskin. “At this point, we’ll have to see how strong it gets.”

That’s not always an easy question to answer months in advance.

El Nino, or “the boy” in Spanish, involves the movement of a vast amount of warm surface water from the western Pacific to the eastern Pacific oceans. It remains difficult to predict more than a hundred years after South American fishermen noticed that it showed up around Christmas and named it after the Christ child.

Forecasters saw signs as early as June that surface waters in parts of the Pacific Ocean were warming up, a sign that an El Nino could form, said Vernon Kousky, a research meteorologist at the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

It will take a couple of months to see exactly how the atmosphere will interact with those warm ocean waters. “Once we know that, we’ll be able to say with more certainty what the effects will be,” Kousky said.

Scientists have had difficulty over the years establishing meteorological patterns that would allow them to forecast when El Nino would appear and how strong it would be. Computer modeling is getting better, helped by an array of research buoys moored in the Pacific.

El Ninos also come in many different variations that the computer models cannot yet capture. For instance, sometimes the warm ocean waters pile up in one part of the Pacific, say, close to the South American coast. Other times, the warm waters collect somewhere else or spread across a larger area.

The differences affect the resulting weather patterns.

“We have a better grasp now than we did 25 years ago,” said Ed O’Lenic, a meteorologist at the Climate Prediction Center. “And we have a whole lot more we need to find out.”

Typically, El Nino occurs every two to seven years, and lasts seven to 12 months, according to the National Weather Service.

El Nino encourages upper-level winds that hinder the formation of hurricanes or sometimes tear them apart. They also can push the jet stream to the south, which helps explain why the South is often stormier during El Nino winters.

The weak to moderate 2002-03 El Nino helped end a long drought in Florida and refill the aquifer. On the other hand, the strong El Nino in 1997-98 ravaged Central Florida with record rains and storms.

That winter, President Bill Clinton declared several counties in Central Florida, including Hernando, a disaster area after rains caused major flooding, mostly along the Withlacoochee River. The bloated river, fed by more than 18 inches of rain in one month, inundated 60 homes and damaged dozens more.

Strong El Ninos also have some links to an increase in tornadoes in Florida.

The El Nino in 1998 and a similar one in 1983 coincided with the two most active tornado seasons in Florida history, according to the National Weather Service. On Feb. 22-23, 1998, tornadoes killed 42 residents, the state’s deadliest tornado outbreak on record.

Researchers, though, are reluctant to say that any single tornado was a result of El Nino. Weak El Ninos don’t appear to have the same influence on tornado activity.

“El Ninos of the magnitude of 1983 and 1998 increase the chances of severe weather outbreaks and stronger … tornadoes simply by providing more opportunities for all the right ingredients to come together,” stated one study.

Florida and the United States have it easy when compared to how El Nino affects more environmentally and economically sensitive regions of the world.

The phenomenon often brings drought and crop failure to southern Africa, where millions go hungry even in good years.

Off South America’s west coast, El Nino diminishes the surge of cold, nutrient-rich water that lets the fish population thrive. In 1972, strong El Nino combined with overfishing caused the Peruvian anchovy fishery to collapse.

El Nino can’t be stopped, even if it made sense to do so. Improved forecasts can help energy companies, water resource managers and farmers prepare and mitigate possible problems, Kousky said.

“El Nino isn’t necessarily bad news,” Kousky said. “It’s knowing that it’s coming that matters.”

Graham Brink can be reached at brink@sptimes.com or (727) 893-8406.