South Florida will be cooler, wetter and potentially more hazardous this winter as a brawny El Nino muscles the Jet Stream out of its normal pattern, pushing it south over the Gulf of Mexico.
The route change to the powerful river of air that regularly flows above more northern regions in winter could increase spats of thunderstorms and tornadoes, the National Weather Service warned Thursday.
In an annual forecast for South Florida’s dry season, meteorologist Robert Molleda said low pressure systems affecting the southern U.S. and Gulf of Mexico increase in years where strong El Ninos are present.
This year’s El Nino is the third strongest on record, according to NOAA.
“Instability, moisture and wind shear come together to cause severe thunderstorms and tornadoes,” said Molleda, the warning coordination meteorologist for the NWS in Miami. “El Nino doesn’t cause the severe weather, but it sets the stage.”
A monster El Nino in 1997-98 contributed to deadly tornadoes in Florida that killed 42 people and injured 365, according to the National Climatic Data Center.
The so-called “Groundhog Day tornado,” which occurred on Feb. 2, 1998, rampaged 21 miles from the Miami International Airport to southern Broward County. It caused $205 million in damage and left hundreds of thousands without power.
Molleda said in the six strongest El Nino years since 1950, the number of dry season EF-1 or greater tornadoes in South Florida was more than double the average of all El Ninos. An Ef-1 tornado has winds from 86 mph to 110 mph.
Most tornadoes occur in February or March, but there’s no trend in what time of day they spin up.
“They can happen any time,” Molleda said, adding that tornadoes are harder to predict than hurricanes. “Many people are unaware of Florida’s severe winter weather risks. They are familiar with hurricanes but not winter weather.”
Nationally, forecasters at NOAA’s Climate Prediction Center said Thursday this year’s El Nino will cause above average temperatures in the west and across northern states, and drier conditions in Hawaii, central and western Alaska, parts of the Pacific Northwest, northern Rockies and areas near the Great Lakes and Ohio Valley.
A wetter winter is also expected for rain-starved California.
“While it is good news that drought improvement is predicted for California, one season of above-average rain and snow is unlikely to remove four years of drought,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center.
South Florida’s drought, which was exacerbated by a slow start to the rainy season, is all but erased following several weeks of normal rainfall.
The U.S. Drought Monitor’s weekly report released Thursday found no drought in Palm Beach County, although 13 percent is still considered “abnormally dry.”
Temperatures in Florida are expected to be 2 to 4 degrees lower than the normal winter average. The 30-year historic high temperature at the Palm Beach International Airport for December through February is between 74 and 76 degrees Fahrenheit. The low is between 56 and 60.
Christian Miller, commercial vegetable and fruit extension agent for UF/IFAS in Palm Beach County, said growers should be aware of how El Nino can impact their winter crops.
Lower yields in green peppers and tomatoes can occur in cooler-than-average winters because of stress on the plants. Root rot and a lack of nutrients because of increased rains are also concerns.
“The challenge is going to be seeing how much rain we get and how frequently it comes because that dictates if farmers can get into their fields to harvest and plant,” Miller said.