Storm Clouds

July 29, 2008 06:18 AM
This year's erratic weather has left many weather-beaten and looking for friendly skies. As ominous clouds continually threatened a soaked Midwest, dryness spread across a parched southeast and Texas. Other regions experienced every weather pattern in between.

Places in Iowa and Nebraska recorded the wettest June ever. Moving eastward from New York down through the Carolinas, it was one of the warmest Junes in recent history. Texas is experiencing the opposite of last year's cool, wet spring, as many locations have only recorded tenths of an inch of rain for the year by July.

Unlike 1993 when heavy rains fell in July and August, this year's moisture came in March and April in the southern Corn Belt and May and June in the northern Corn Belt.

"This year, four weather factors converged that led to the weather we had in the Midwest: the Bermuda high pressure, low pressure in Colorado, the Reman Index and the Jet Stream,” explains Iowa State Extension climatologist Elwynn Taylor. "The low over Colorado is not a typical summer resident or spring resident because normally the low pressure over the Rocky Mountains moves to Canada.”

Taylor explains the Bermuda high pressure arrived outside its typical time window. Meanwhile, the Reman Index, which quantifies the warm moist air from the Gulf of Mexico to the Midwest, was a much stronger flow than usual. Another major influencer was the Jet Stream from the southwest to the northeast, which is not a typical resident of the High Plains.

When those conditions aligned, the spring planting season turned cool and wet and ground-saturating rains followed.

The amount of precipitation that fell across much of the Corn Belt was 200% to 400% above normal based on a 30-year average, according to Planalytics meteorologist Jeff Doran.

"A common question is why are we having more 200- or 500-year floods?” Taylor says. "Well, our climate has changed. The Midwest receives about 10% more annual precipitation than the years before 1970, which in turn has doubled the annual stream flow across the region, and rivers are more often out of their banks.”

Taylor explains Illinois, Iowa, Wisconsin, Indiana and South Dakota are all experiencing typical annual stream flow with six times as many flood events since 1970. With his calculations and our current climate, he expects 200-year events to take place in 26- to 28-year time frames.

"The annual precipitation has increased at essentially all locations east of central Nebraska and north of Florida, and this has caused the shortening of the time between major floods,” Taylor explains. "We don't know if it's a permanent change to precipitation or if it's a cyclic change.”

The good news for now is that the worst should be behind us in 2008.

"Heading into July from June, is when we turned away from this spring's pattern of heavy rain in the Midwest,” Doran says. "In fact, some of these rains will head south and east, which will help those folks.”

With an above average tropical storm and hurricane season expected, as well as an impending frost on late planted and delayed crops, it'll be important to keep eyes to the skies and ears on the forecasts.

You can e-mail Margy Fischer at

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