DES MOINES — As summer officially closes Monday, and thoughts increasingly turn to scraping ice and shoveling snow, early indicators suggest Iowa’s winter might not be as extreme as last year’s.
You remember the one that delivered a “polar vortex” punch with record-low temperatures and a “bomb cyclone” that flooded huge swaths of the state? Farmers were stung and millions of dollars worth of roads destroyed, leading to rebuilding that continues today.
Jerry Schnoor, co-director of the University of Iowa’s Center for Global and Regional Environmental Research, said the hope is that Iowa will see a more typical winter this season.
“Hopefully, that (polar vortex) won’t happen this time,” he said. “Let’s hope that doesn’t play out again.”
But weather and climate experts caution it’s too early to forecast that far in the future with a high degree of certainty. One indicator that gives experts a sense of Iowa’s winter-to-be is the prediction that there won’t be an El Niño in the Pacific Ocean.
Last winter, an El Niño — when surface water temperatures rise in the ocean off the coast of South America — caused a weakened jet stream. That’s a band of air currents that crosses the ocean. It led to frigid lows across the Midwest.
In January, Iowa experienced record low temperatures of 30 below or colder, with wind chills reaching more than 50 below.
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With early projections suggesting no 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 expert predictions suggest a La Niña — when those same ocean surface waters cool — that could lead to wider-than-normal temperature swings during Iowa’s winter.
That would mean extreme cold spells but also unusually warm periods, Gallus said.
If there is neither an El Niño or La Niña, 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.”
The National Weather Service’s Climate Prediction Center says there is an equal chance of above- and below-average temperatures in Iowa for 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 the notion that it is too soon to forecast Iowa’s winter with any degree of certainty, but said Climate Prediction Center has the most reliable long-term forecast. Like any other year, Iowans should brace for extremes.
“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 that Iowa appears to be safe from the possibility of an early freeze. That is good news for the many Iowa farmers who started their growing season late because of spring floods.
As a result of the late start, crops are weeks late reaching maturity.
In the latest report from the U.S. Department of Agriculture on Iowa crop progress — as of Sept. 13 — 8 percent of the state’s corn crop has reached maturity. That’s 19 days behind last year and 13 days later than average.
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The report found that 96 percent of the soybean crop was producing pods — but that was more than two weeks behind the average.
Glisan said multiple trends suggest Iowa won’t have an early freeze this year, which is defined as 32 degrees for frost on the ground and 28 degrees for killing plants.
The first freezes in Iowa typically are 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 effect on Iowa infrastructure, especially flooded roads in the western portion of the state.
A “bomb cyclone” in March ushered in blizzard conditions, hurricane-force winds, snow and rain. The storm walloped the Missouri River, blowing out levees and inundating huge tracts of western Iowa and eastern Nebraska. At least seven highway segments — including parts of Interstate 29 — were severely damaged.
Worse for farmers, the flooding took out scores of gravel roads necessary for getting commodities to market.
The Iowa Department of Transportation expects all necessary repairs to be finished by the end of the construction season — provided no further damage is created by more 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.