‘This is what we would expect from climate change’

Source: Daniel Cusick, E&E News reporter • Posted: Friday, April 12, 2019

MINNEAPOLIS — More than 10 million Americans are seeking shelter this morning from rain, sleet, snow, hail, ice and wind as one of largest spring storms on record churns across the Great Plains into the Missouri and Mississippi river basins.

The storm, created by a powerful collision of cold and warm air masses over the central Rockies and western plains, has been described by some as a “bomb cyclone,” a technical term referring to an atmospheric pressure drop of at least 24 millibars over 24 hours.

This week’s storm may fall just short of the 24×24 definition, experts say, but it bears striking similarity to an earlier bomb cyclone that tracked across the same region of the country in mid-March.

“We’re seeing a very similar path to that [earlier] storm,” said Marc Chenard, a meteorologist at NOAA’s National Weather Prediction Center in College Park, Md. “That one was a little stronger, and it intensified quicker and deeper. We may not get the same extremes out of this one, but it’s not going to be too far off.”

As of yesterday afternoon, atmospheric pressure at the storm’s center had dropped 19 millibars and was still falling, Chenard said. Much of the storm’s precipitation was trending north, he said, meaning it could produce more snow than rain.

Experts say such storms, which undergo a rapid intensification process called “bombogenesis,” are not uncommon in the spring.

But the close timing and high intensity of the recent storms have raised new questions about whether the middle of the country is experiencing a distinct climate change signal, just as the Atlantic and Gulf coasts have seen a recent rise in hurricane frequency and intensity.

Andreas Prein, a climate scientist and expert on extreme weather events at the National Center for Atmospheric Research, said it is certain that this year’s Midwest cyclones, like other extreme events, are influenced by changes in the climate.

These include higher average air temperatures that fuel warm, wet air masses drifting up from the Gulf of Mexico. Pronounced shifts in the jet stream also cause greater temperature swings across North America and can intensify weather where very warm and very cold air meet.

“In many ways, this is what we would expect from climate change,” Prein said from NCAR’s offices in Boulder, Colo., which saw a 50-degrees-Fahrenheit drop in temperature between Tuesday and yesterday. “The stronger the temperature gradient between the cold air in the north and the warm air in the south, the more intense these cyclones will be.”

Blowing snow was accumulating last night as far east as Minneapolis-St. Paul. The National Weather Service issued high wind and red flag fire warnings from Missouri to southern Arizona, where low humidity, high wind and dry vegetation have turned millions of acres into a tinderbox.

Officials said heavy snow across portions of Nebraska, South Dakota and Minnesota will also exacerbate already severe flood damage across the Midwest, especially on the Missouri River, which saw record flooding in parts of Iowa, Nebraska and Missouri less than a month ago.

Republican governors of those three states issued a public plea last week to the Army Corps of Engineers and the Federal Emergency Management Agency to help flood-ravaged communities “in cutting red tape and rebuilding bigger and better than before to keep people safe.”

The March extreme weather caused breaches to dozens of levees, both federal and nonfederal. State and local officials remain unsure how they will be repaired, who will pay and at what cost.

Yesterday’s storm was also disrupting air travel to and from hub airports like Denver and Minneapolis. It may resubmerge critical rail and road infrastructure as runoff from heavy rain and melting snow enters the Missouri and Mississippi river basins late this week and early next.

The nation’s two largest railroads, Union Pacific and BNSF, said last week they had reopened most of the rail lines affected by the March floods. Spokespersons for the two railroads did not respond to inquiries yesterday.

In an April 5 notice to customers, Union Pacific Executive Vice President Kenny Rocker said workers had “made significant progress restoring operations throughout the Midwest, and as a result, our performance metrics are showing signs of improvement.”

Farmers remain among the most vulnerable to the extreme weather. They faced $1 billion in damages to farm property, equipment, buildings and other essential infrastructure during last month’s floods.

Many farmers are also worried about field conditions after the water recedes, as saturated soils and erosion create delays in spring plantings. One small consolation for farmers is that soils have had several additional weeks of thawing, which will improve absorption capacity.

Snow totals were expected to be deepest in eastern South Dakota and southwestern Minnesota, where as much as 30 inches of new snow were forecast through tomorrow.

South Dakota Gov. Kristi Noem (R) closed nonessential government offices in 52 counties and reopened the state’s Emergency Management Center as weather conditions deteriorated yesterday. “We’re calling it historic because of the widespread heavy snow. We will set some records,” Mike Connelly, a NWS meteorologist in Aberdeen, S.D., told the Associated Press.

The governors of Minnesota and Colorado said National Guard troops would be ready to assist citizens in need. Officials in Colorado closed a 150-mile stretch of Interstate 76 from east of Denver to the Nebraska border, the AP reported.

Minnesota could challenge a decade-old record for a single April snowstorm. A spring blizzard in 2008 dumped 32 inches in northeast Minnesota, according to records kept by the Department of Natural Resources.

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