Abnormally warm nights settled over Palm Beach County this week, tying decades-old heat records with temperatures 12 degrees above average.
The National Weather Service in Miami measured low temperatures Tuesday and Wednesday that dipped to just 75 degrees at Palm Beach International Airport, equaling balmy benchmarks set for those days in 1990 and 1997, respectively.
The normal overnight low temperature for this time of year is 63 degrees.
An easterly breeze blowing over the warm waters of the Atlantic is being blamed for the lack of nighttime cooling, but a miserly jet stream has also kept wintertime air locked up far from South Florida’s reach.
Dan Kottlowski, a senior meteorologist with AccuWeather, said the jet stream has been stretched straight east to west across the top third of the U.S., trapping frigid air to its north.
“All the storm systems are moving from west to east very quickly along that northern portion of the U.S., and fast-moving storms don’t allow cold air to press very far south,” Kottlowski said. “There’s no way for cooler air to come down into the Palm Beaches.”
It’s a pattern typical during La Niña — a climate condition that emerged in October and is forecast to continue through winter. La Niña usually results in a warmer, drier winter for South Florida.
“We just haven’t had any real cold blast of air, and that’s not unprecedented, especially in a La Niña year,” said Robert Garcia, a meteorologist with the National Weather Service in Miami. “We’re still a little early in the season.”
Temperatures are forecast to remain above normal through the weekend, with highs in the low 80s and overnights in the high 60s to low 70s.
Beyond that, forecasts differ on when a pattern change may force cooler air south.
Garcia said he saw nothing in the 10-day forecast that led him to believe a cold front was imminent.
Kottlowski is more optimistic, saying a “major change” is coming next week after a strong storm system rolls into the Pacific Northwest, triggering the jet stream to take a dive as far south as Florida’s Panhandle. That will mean a cooler northwest surge of air into South Florida.
“Thursday next week will be the big change,” Kottlowski said. “The latest computer forecast has temperatures not much higher during the day than in the 60s.”
With the front will be an increase in showers, which could be good news for the Panhandle. The U.S. Drought Monitor report released Thursday showed abnormally dry to moderate drought conditions stretching from Pensacola into the Big Bend area.
The water situation is reverse in parts of South Florida with coastal Palm Beach County and Broward ending November with a surplus of rainfall. Coastal Palm Beach County got an inch more rain than normal, with parts of Broward seeing nearly four inches above average.
Still, it’s been dry enough that the Army Corps of Engineers announced Thursday it is reducing water discharges from bloated Lake Okeechobee for the second consecutive week. The lake was 16.12 feet above sea level Thursday.
That’s higher than the 15.5 feet the corps prefers to cap water levels at, but more than a foot below its post-Hurricane Irma high of 17.2 feet.