A building El Nino in the Pacific Ocean may create wet and wild conditions for Central Florida this winter.
So far this year, we've seen a quiet hurricane season because the warm ocean temperatures in the Pacific that create an El Nino tend to suppress hurricane activity. However, that ocean current produces the opposite effect in the winter.
The Pacific jet stream moves south and pushes powerful winter storms across the Gulf of Mexico, bringing all kinds of severe weather, especially to Central Florida.
Seven of Florida's 10 deadliest tornadoes, including the killer tornadoes of 1998 and 2007, occurred during El Nino winters, said Bart Hagemeyer, meteorologist-in-charge of the National Weather Service office in Melbourne.
While forecasters say this El Nino will likely be moderate, forecasters are never sure "exactly what each El Nino will bring," Hagemeyer said Tuesday. But, they know "the relationship between strong El Ninos and violent tornado outbreaks is very strong."
El Nino also causes hail storms, powerful thunderstorms and flooding rainfall.
Although forecasters aren't sure why, many winter tornadoes during El Nino years tend to be stronger and strike at night, while people are sleeping and the least prepared. A study of statistics for wintertime tornadoes since 1950 shows many more people die when tornadoes strike overnight.
That worries weather service forecasters and emergency managers, who hope to get the message out to residents and visitors that extra vigilance will be needed this winter.
The weather service is examining its warning tools and messages to look for better ways to communicate the dangers from approaching storms, said Scott Spratt, the warning coordination meteorologist in Melbourne. For example, if a storm appears to carry a particularly strong risk of tornadoes, the weather service might warn people living in mobile home communities to consider spending the night with friends in a safer location.
Families and individuals should prepare just like they do for hurricane season, Spratt said, making sure they have a plan for where they will seek safe shelter when a tornado watch is issued.
Forecasters usually have considerable lead time to say when a violent weather system may be approaching, possibly several days in advance, he said. They may even be able to issue a watch, meaning conditions are favorable for a tornado, several hours in advance.
They have much less time to warn of an actual tornado. Spratt said the goal is 12 minutes.
Recent winter tornadoes typically moved across the state at about 50 mph or just about a mile a minute, Hagemeyer said.
"Getting the warning out and being able to take action fast is critical," he said.
The weather service encourages people to buy weather radios that give audible alerts in advance of severe weather events. They also have begun advising people to subscribe to services that send weather alerts in text messages to cell phones as a backup plan.
A few positive things accompany an El Nino, Hagemeyer said. It reduces the chance of drought and wildfires. And, even though it might bring more days of cooler temperatures, it minimizes the risk of severe freezes that occur when conditions in the Pacific are more neutral.