There’s a high probability this fall will be warmer and wetter than normal, according to a prediction from the National Weather Service’s Climate Prediction Center.
The center estimates Vermont has a 60% chance of higher temperatures and 40% chance of more precipitation than the 30-year normals based on data from 1991 to 2020.
The fact that it’s based on previous data is key, said Peter Banacos, science operations officer at the National Weather Service Burlington office.
“There’s a natural tendency for the temperatures to be above the 30-year climate average, just because of global warming,” Banacos said. “So it does tend to lean on the warmer side generally.”
Another factor is La Niña, the second half of the El Niño Southern Oscillation cycle, a naturally-occurring phenomenon in the equatorial Pacific Ocean where surface water is warmer (El Niño) and then cooler (La Niña) than usual, with a neutral period in between. The center estimates a 66% chance of La Niña forming in the fall and a near-70% chance of it persisting in the winter.
“Because the polar jet stream (the one that affects us in the mid-latitudes) dips over the eastern part of North America during La Niña events, you'll see that we tend to have wetter and warmer conditions during the winter,” State Climatologist Lesley-Ann Dupigny-Giroux said over email.
A La Niña event is also associated with a more active hurricane season in the Atlantic.
While the estimates show an increased likelihood of warmer temperatures and more precipitation, there is still a possibility temperatures and precipitation will be the same as or below the 30-year normal.
The last couple of years have been warmer than they were in the recorded past, with seven of the 10 highest average fall temperatures recorded in the last 13 years – last year, the 91-day period between Sept. 1 and Nov. 31 was the sixth-warmest on record.
Have questions, comments or tips? Send us a message. Or contact the reporter directly at corey.dockser@vermontpublic.org.
