Stay on the weather roller coaster
By Janet Kubat Willette
Date Modified: 03/05/2013 9:16 AM
Iowa State University Extension climatologist Elwynn Taylor expects the variable weather pattern of warmer than normal temperatures followed by colder than normal temperatures to continue through March.
Taylor follows the North Altantic Oscillation. When the North Atlantic Oscillation is positive, the eastern United States tends to have milder winters. When the North Atlantic Oscillation is negative, the eastern United States tend to have harsher winters.
From the 1950s up to about 1980, the oscillation was negative and winters were harsher in the area. Winters were milder through 2010, when Minnesota and Iowa experienced what most people would refer to as an old-fashioned winter.
Taylor wonders if the oscillation is switching to a negative after about 30 years of being positive.
But the amount of snow received in winter won't help recharge dry soils. Instead, it runs off the ground and into streams causing ice jam floods in some cases. There's been some localized short-term flooding in recent weeks because water can't infiltrate frozen ground, Taylor said.
Water is needed in the soil, especially in the western half of the Corn Belt, west of Interstate 35. There is plenty of water up the Ohio River Valley, Taylor said. At this time tiles are running in Ohio, Indiana and Illinois.
Those who remember the drought of 1988 remember it wasn't really so bad in western portions of Minnesota, Iowa and Nebraska, rather it was the drought of 1989 in those regions. This drought has similar characteristics, he said.
Oftentimes, the weather is different east and west of Interstate 35. The rule of thumb is that weather west of Interstate 35 is seasonally controlled by what is going on in the Pacific Ocean. The weather east of Interstate 35 is controlled by the Atlantic Ocean, including the Gulf of Mexico.
The big controlling factor for summers is the Bermuda High pressure on the Atlantic side of things. Much of the precipitation that falls in the Midwest comes from the Gulf of Mexico, forced up because of the Bermuda High pressure. Without the Bermuda High, the upper Midwest would be the great desert rather than the nation's breadbasket.
In 1988, the Bermuda High pressure didn't form until July. By that time, the crop was lost.
This year, the Bermuda High is acting like it's in place now. That's why the state is getting so much fog. Winter fog is the breathe of the Gulf of Mexico, Taylor said.
The Bermuda High isn't supposed to come until after March 10, he said. If it's early, expect more fog and more ice storms. It may also bring a wet spring to alleviate the drought.