Warmer, drier winter predicted
Forecasters point to likely La Niña; state on three-year heat streak.
A warmer, drier winter is forecast for the Sunshine State as a drowsy La Niña awakens from a summer slumber.
The forecast, which will disappoint those hoping for a break in a 3-year run of above-normal temperatures statewide, was released Thursday by NOAA’s Climate Prediction Center as part of its 20172018 winter outlook.
A key indicator for the longrange prediction is the climate pattern La Niña, which has up to a 65 percent chance of appearing during the next few months. The center, based in College Park, Md., put Earth on a La Niña watch in September.
“The way this weak La Niña is evolving is very similar to last year,” said Florida Climatologist David Zierden. “There are a few mixed signals. A 65 percent chance of it happening means a 35 percent chance that it won’t happen, so there is a level of uncertainty.”
La Niña is marked by cooler-than-normal temperatures in the tropical Pacific Ocean, which trigger widespread changes in the atmosphere that tend to straighten the jet stream. Instead
of an undulating river of air that dives deep enough to blast cold fronts through Florida, a straighter jet stream keeps arctic air confined to the northern reaches of the continental U.S.
During La Niña years, Florida’s temperatures usually average 2 to 4 degrees above normal and rainfall averages 40 to 60 percent below normal.
In the December through February forecast, only a sliver of areas from Oregon through Minnesota are expected to have below-normal temperatures this winter,
whereas a vast swath from California into the southeast and north through New England is predicted to be warmer than normal.
“I don’t expect La Niña to fizzle,” said Mike Halpert, deputy director of the Climate Prediction Center. “The odds favor an elevation to advisory next month.”
While the National Weather Service in Miami has yet to issue its winter forecast, meteorologists in the Melbourne office agree with the Climate Prediction Center’s assessment, calling for less storminess and more sunshine along the Treasure Coast and in Central Florida.
Statewide, Florida has been on a heat streak since 2015. The average annual temperature that year was 2.2 degrees above normal. In 2016, the year-end average temperature was 2.4 degrees above normal. And this year, through September, the average temperature has been 2.5 degrees above normal.
While Halpert said he doesn’t expect this year to break 2015’s record as the second-hottest for the U.S. on record, Zierden said it’s hard not to see a trend toward a warmer world.
“We certainly have been warming since the cooler period in the 1970s and the fact that we’ve been on a 3-year run in Florida, certainly climate change has something to do with that,” Zierden said.
If a weak La Niña develops, it will be the second consecutive year for the pattern to dominate weather in North America — something Zierden said is not unusual.
But unlike 2016 when Florida entered the dry season abnormally parched, which led to 70 percent of the state suffering from drought by May, this year is flush with water. As of Wednesday, the seasonal rainfall total for the 16-county region overseen by the South Florida Water Management District was 15 inches above normal.
Lake Okeechobee was at 17.10 feet above sea level on Thursday, significantly higher than the 15.5-foot cap the Army Corps of Engineers prefers to maintain to keep the Herbert Hoover Dike from eroding.
Still, wildfires remain a concern this winter. Vegetation fed by heavy summer rain can dry out quickly during winter months, becoming fuel for wildfires. This year, Hurricane Irma also downed trees that will increase fire dangers in unmanaged areas.
“We have a lot of wildland area, and as things dry up, those trees that fell over won’t have any moisture,” said Scott Peterich, wildfire mitigation specialist for the Florida Forest Service. “They will add to the fire risk.”