Serving Minnesota and Northern Iowa.

Seeley: State's weather is changing

By Janet Kubat Willette

Date Modified: 04/19/2013 3:13 PM

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The flood threat in the Red River Valley and upper reaches of the Minnesota River Watershed are real and can be expected to materialize this week if forecast precipitation and warmer than normal temperatures materialize, Mark Seeley said last week during a climate webinar.

Seeley, University of Minnesota Extension climatologist, was the featured speaker in an April 2 Minnesota Association of Soil and Water Conservation Districts and University of Minnesota webinar.

He advised people in the valley and upper reaches of the Minnesota River Watershed to pay close attention to information from the National Weather Service.

The heightened flood awareness comes at the same time that 67 percent of Minnesota's landscape is in severe to extreme drought, according to the U.S. Drought Monitor. This is a result of last year's weather conditions. Areas to the south and west of Minnesota are in worse condition, Seeley said.

The spring weather outlook favors an alleviation of drought for Minnesota, with abundant precipitation forecast this spring for all of Minnesota and a good portion of Iowa.

Looking back, 2012 was a record-setting year, Seeley said. Mean monthly temperatures easily surpassed all other years, with readings dating back to 1895. The entire United States was warmer than normal. Normally, some states are warmer, colder and near normal in the same year. This widespread temperature abnormally is rare, he said.

The second weather headline of 2012 was the drought. More than 2,200 counties in the nation were declared agricultural drought disasters, surpassing any previous record.

Much of the weather data he compiles is collected by volunteer weather observers throughout the state. Minnesota's observation network is probably one of the best in the country, Seeley said. It would be impossible to document changes in Minnesota's climate patterns without the work of volunteers. Some families have been volunteer weather observers back to the 19th century, he said.

Minnesota's climate is changing. Some of the fluctuations are due to normal variability, but others are due to changes in land use and changing atmospheric composition. Three independent world data sets show pronounced change in precipitation, temperature, cloud patterns and storm severity.

The more pronounced temperature change in Minnesota is occurring from December through February, with warmer temperatures.

The last 15 winters have been warmer than normal with the winter of 2011-12 being the mildest winter in state history. The winter of 2012-13 was closer to the middle of the pack, though it seems like conditions went back to arctic compared to last year, Seeley said.

The average January minimum temperature has changed by three degrees in Austin, while temperatures in November and December have changed by more than 2 degrees. The same changes are occurring in Brainerd and Willmar, he said.

Changes have occurred in summer, too. There is an increasing frequency of warm nights, when the nighttime temperature doesn't drop below 75 or 80 degrees.

More tropical days are occurring. The 80 degree dewpoint was non-existent in Minnesota until the modern era. The state has had 80 degree dewpoints in each of the past three summers.

As a result of the high dewpoints, the National Weather Service is issuing more heat index warnings.

At 6 p.m. July 19, 2011, the hottest place on earth was Moorhead. The temperature was 97 and the dewpoint was 88, making the heat index 134. Seeley said they thought it was an instrument error, but it wasn't and the heat and tropical dewpoint was widespread across the Red River Valley.

While dewpoints have risen, the number of triple-digit temperature days have fallen. They occurred in olden times in the state, Seeley said.

Climate change is also impacting precipitation. The seasonality isn't as distinct as with temperature, with summers and winters mixed, Seeley said. However, springs and falls have mostly been wetter than normal in the modern era.

Minnesota missed out on the precipitation last fall, however.

Seeley said the southeastern part of the state averaged over 29 inches of precipitation from 1891 to 1921, with the rest of the state getting lesser amounts. From 1921 to 1950, only seven southeastern counties received that much precipitation. For the 30-year period beginning in 1981, close to half the state landscape averages close to 29 inches or more of annual precipitation.

More of the precipitation is falling in thunderstorms, which occur with greater frequency . It's now the exception to get through a year without a damaging flash flood. There were three, 1,000 year flash floods in southeast Minnesota since 2004.

However, the granddaddy of all flash floods in Minnesota took place July 17-19, 1867, when 30 to 36 inches of rainfall fell over the Pomme de Terre and Chippewa River watersheds. It was the only time a 12 foot rise on the Mississippi was measured in 24 hours.

There were 37 tornadoes in Minnesota last year, which is close to normal in the modern era, Seeley said. The interesting thing was they occurred early (March 19 in Waseca County) and late (Nov. 10 in Washington County.)

More frequent drought is occurring in Minnesota, with drought impacting part of the state in 2007, 2008, 2009, 2010, 2011 and 2012. The last similar period of dryness occurred in the 1930s.

In 2007, both flood and drought disaster declarations were declared. It was the first time that happened with 24 counties declared drought disasters and seven counties declared flood disasters, Seeley said.

Last year, 55 counties were declared drought disasters and 11 counties were declared disasters for flooding.

The state's changing climate has many consequences, Seeley said. Growing seasons are longer, which results in changes in the plant hardiness zones. There is shorter duration of soil and lake freezing. Fall nitrogen applications are pushed later as the soil stays warmer. The winter survival rates of biological organisms is improving with mild winters. Fisheries management is changing. The changing weather may open the door for more invasive species. The number of freeze and thaw cycles that impact roadways are increasing. The mold and allergen season is longer, more health advisories and more attention to drainage and irrigation management.

Since 1980, the United States has had over a trillion dollars in insured infrastructure losses. 2012 will be a record year for loss becase of Superstorm Sandy and the widespread drought, Seeley said.

In his opinion, a failure to respond to the changing climate is a serious error in judgment.