A feeble La Niña is here, a signal that Florida will experience a drier and warmer winter as the atmosphere responds to a subtle chill in the equatorial Pacific Ocean.
Federal forecasters from the National Oceanic and Atmospheric Administration declared this morning that a weak La Nina was in place and could last thruogh winter.
Earlier this year, NOAA released its winter forecast with the idea that La Nina would occur. The forecast divides the country like a layer cake with abnormally wet and cold winter conditions in some northern states, and the likelihood of above average temperatures and less rainfall in a southern swath that stretches from California to the Mid-Atlantic.
A middle section of the country, which includes much of the northeast, is in a winter forecast limbo where conditions could go either way or end near average.
For Florida, the prediction of a warmer, drier winter is radically opposite last year’s forecast when the so-called Godzilla El Niño dominated and record rainfall fell on the Sunshine State.
“With much of the state fairly saturated right now from the tropical systems, and with the heavy El Niño winter rains last year, a spell of drier weather might be welcome in the short term,” said Florida Climatologist David Zierden.
During La Niña years, Florida’s temperatures usually average 2 to 4 degrees above normal and rainfall averages 40 to 60 percent below normal, Zierden said.
But he cautioned about buying wholesale into La Niña making a full-fledged appearance.
The forecast for La Niña has been up and down since spring. Originally, the periodic event was given a 75 percent chance of development. That dropped to between 50 and 65 percent over the summer, but is now back up to 70 percent.
The Climate Prediction Center has put Earth on a La Niña watch, meaning conditions are favorable for La Niña to develop within the next six months.
“Even though NOAA increased the chances to 70%, we are still in a wait and see mode on the strength and longevity of a possible La Niña,” Zierden said. “Week to week changes in sea surface temperature (and forecast models) can often be misleading, as you have seen with the on again, off again waffling of the NOAA forecasts.”
La Niña conditions occur when waters in the equatorial Pacific Ocean cool, pushing thunderstorm patterns toward Indonesia and changing upper air flows high in the atmosphere.
“It shifts the Jetstream more to the west and results in more storminess in the Ohio Valley, leaving the southeast high and dry,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center about La Niña. “If you didn’t have these events, the western Pacific would warm continuously. This evens out the heat content.”
Thursday’s winter prediction follows a Wednesday announcement from NOAA that last month ended a 16-month streak of record-breaking heat, coming in runner-up for hottest September in measurements dating back to 1880.
NASA, which puts out its own global temperature report, disagreed with NOAA’s September ranking as second warmest, putting it in first place for the hottest on record.
But scientists from both organizations widely agree 2016 is on pace to beat 2015 for hottest year on record, which took the title from 2014.
“We continue to stress that while monthly rankings are newsworthy, they are not nearly as important as long-term trends,” director of NASA’s Goddard Institute for Space Studies in New York.
Florida’s average temperature January through September was 73.6 degrees, which is 1.8 degrees warmer than normal, according to NOAA.
For southeast coastal Florida, including Palm Beach County, the average temperature through September was 77.3 degrees, which is 2.4 degrees above normal.
Ed Vallee, a meteorologist with AccuWeather, which issued its winter forecast earlier this month, said just because the overall trend for Florida is warmer and drier, doesn’t mean there can’t be cooler days and freezing temperatures in central and northern parts of the state this winter.
“Generally, we have a fairly decent amount of confidence in the seasonal outlook as a whole,” said Vallee, who noted that AccuWeather’s winter forecast was similar to NOAA’s. “But it’s very difficult to pinpoint specifics as to what kind of weather will happen on what day.”