El Niño has brought Floridians a calmer hurricane season, but the winter could be a much different story.
Think downpours, floods and tornadoes.
"We're going to have a very active winter," said Daniel Noah, the warning coordination meteorologist for the National Weather Service in Tampa Bay.
No hurricanes have threatened Florida this season, which ends Nov. 30. But tornadoes have killed more people in Florida than hurricanes in recent years, so the National Weather Service is trying to get the word out about the flip side of El Niño.
El Niño forms every three to five years as warm surface waters in the Pacific Ocean shift from the west to east. Those warmer waters form upper atmospheric storms that can thwart hurricanes forming in the Atlantic.
But they can also cause havoc during the winter months.
This El Niño started in July and weakened eight hurricanes, Noah said. Now considered a moderate El Niño, it is expected to strengthen in the coming months, producing hazardous weather.
The opposite of El Niño — La Niña — occurs when surface water in the eastern Pacific cool to below average temperatures. That produces warmer winters, drier summers and a more active hurricane season in the Atlantic.
The last El Niño was during 2006 and 2007, and it led to the Christmas Day tornadoes that damaged about 100 homes in Pasco County.
Later that season, parts of Central Florida near Ocala were hit with tornadoes that struck at night and killed 21 people, damaged hundreds of homes and knocked out power to 40,000 households.
Since 1892, Florida's 10 deadliest tornado days all occurred during an El Niño.
Tornadoes are far less predictable than hurricanes, which makes them potentially more deadly. The weather service plans a briefing Wednesday to spread the word about the potential dangers this winter.
Tornadoes have killed far more people in Florida in recent decades than hurricanes.
Since 1950, tornadoes have killed 185 people in Florida, while 66 deaths are blamed on hurricanes or tropical storms, according to the National Oceanic and Atmospheric Administration.
"Even though your chances of being hit by a tornado are small, somebody will be hit and we want them prepared," Noah said.
Every El Niño is unpredictable, experts warn. Some disastrous hurricanes have occurred during El Niño years, including in 2004 when Frances, Ivan, Charley and Jeanne killed more than 3,000 people around the world.
Computer models suggest this El Niño will die in late spring and won't affect next year's hurricane season, said Jeff Masters, a founder of wunderground.com.
But, he warns, "we don't have any skill forecasting out an El Niño six months in advance."
Times researcher Shirl Kennedy contributed to this report. Andy Boyle can be reached at firstname.lastname@example.org or (727) 893-8087.