DES MOINES — As summer comes to a close, early indicators seem to suggest Iowa’s winter may not be as extreme as last year’s, which included a polar vortex that contributed to record low temperatures.
Jerry Schnoor, co-director of the University of Iowa’s Center for Global and Regional Environmental Research, said the hope is that will mean a more normal winter in Iowa this year.
“Hopefully that (polar vortex) won’t happen this time,” Schnoor said. “Let’s hope that doesn’t play out again.”
But weather and climate experts also caution it is too early to forecast the Iowa winter with a high degree of certainty.
One indicator that helps give experts some sense of Iowa’s winter-to-be is the prediction there will not be an El Niño in the Pacific Ocean.
Last winter, an El Niño — when surface water temperatures rise in the Pacific Ocean off the coast of South America — caused a weakened jet stream — a band of air currents that crosses the ocean — which led to frigid temperatures across the Midwest. In January, Iowa experienced record low temperatures in the 30s below zero, with wind chills reaching the 50s below.
With early projections suggesting there will not be an El Niño this year, experts said the hope is there will be no repeat of the polar vortex.
Bill Gallus, a professor in Iowa State University’s geological and atmospheric sciences department, said some experts are predicting a La Niña — when those same Pacific Ocean surface waters cool — which could lead to larger than normal temperature swings during Iowa’s winter. That would mean extreme cold spells and also unusually warm periods, Gallus said.
‘Far less predictable’
If there is neither an El Niño or La Niña, the winter becomes far less predictable, especially this far out, experts said.
“The best answer is we really cannot predict what this winter will look like. Being Iowa, there will surely be some intense cold spells and a few snowstorms, but there is no way to know if they will happen much more than normal, or less than normal,” Gallus said.
“Sometimes, as we get closer to winter, such as in November, we may be able to have a bit more skill because we may start seeing the jet stream behave in a consistent fashion, and we can guess that this pattern might repeat itself often, at least into the start of winter. However, September is too early to tell.”
The National Weather Service’s Climate Prediction Center says there is an equal chance of above and below temperatures in Iowa for the months of December, January and February, and a slightly above average chance of higher than average precipitation during the same months.
Iowa state climatologist Justin Glisan echoed other experts’ notes that it is too soon to forecast Iowa’s winter with any degree of certainty, but said the National Weather Service’s Climate Prediction Center has the most reliable long-term forecast.
Gallus said like any other year, Iowans should prepare for anything this coming winter.
“With no signals out there yet to help us predict the winter weather, Iowa residents should be prepared for just about anything that could happen in winter, including severe cold and wind,” Gallus said. “The best advice is to be prepared for the worst that winter can throw at us, since this is Iowa, and even warmer than average winters here are still cold enough to allow big snowstorms.”
More certain, Glisan said, is Iowa appears to be safe from the possibility of an early freeze. And that is good news for the many Iowa farmers who started their growing season late because of spring floods.
Glisan said multiple trends suggest Iowa will not have an early freeze, which is defined as 32 degrees for frost on the ground and 28 degrees for killing plants.
The first freezes in Iowa typically occur starting in early October in the northern counties, Glisan said.
“We were cooler than average in August, and we’ve flipped the script and now we’re accumulating growing days (in September), helping that late push for corn, which is great news,” Glisan said.
The rough winter and spring flooding had an adverse impact on Iowa infrastructure, especially flooded roads in the western portion of the state.
But the state transportation department expects all necessary repairs to be finished by the end of the construction season, provided no further damage is created by any more potential flooding.
The only exceptions, a state transportation department spokeswoman said, are ongoing repairs on Iowa Highway 2 in southern Iowa and Iowa Highway 333 around Hamburg in southwest Iowa, the area hardest hit by flooding.