A climatologist at the National Drought Mitigation Center says a “flash drought” may spread across Iowa in the next week. Climatologist Mark Svoboda says the “epicenter” of the drought has been in northern Illinois, southern Wisconsin and eastern Missouri. “But given the time of year we’re in, it doesn’t take much of a hot, dry period. Temperatures are expected to build back in under this high pressure ridge, and so you could really see that push westward rather quickly,” Svoboda says. The forecast calls for an extended period of high temperatures in the 90s. He says there’s the potential for a “flash drought” because this is the time of year when crops are in a critical stage of development. “Late July/August is typically the time of year where we can see a two-week prolonged period…of both hot and windy conditions which can really sap a crop in a hurry,” Svoboda says. While we often say “it’s not the heat, it’s the humidity,” Svoboda says when it comes to drought, it’s not just the heat, it’s the wind. Windy conditions can “wick away” moisture from plants — in the range of up to half-an-inch-a-day — during periods of drought. That means climatologists like Svoboda review not just tempertures and humidity but wind speeds to determine how quickly an area may enter a drought. The position of the Gulf Stream is a major cause of this year’s drought that’s already raging in Illinois. High pressure has been “camped out” over the plains, according to Svoboda, which means thunderstorms from the Gulf of Mexico fizzle out when they reach the Midwest. For example, Hurricane turned tropical storm Dennis plowed itself up the Mississippi and Ohio River Valleys, but wasn’t nearly the “rain-maker” it might have been. Svoboda says year-to-date precipitation levels show western Iowa has been in better shape than eastern Iowa. But he says since the middle of May, the entire western half of Iowa has received just 50 percent of normal precipitation for that 60 day period. “Drought’s about timing, timing, timing,” Svoboda says. You can hear Radfio Iowa’s entire interview with Svoboda on www.radioiowa.com. In early August, the central region headquarters of the National Weather Service will host a meeting of weather forecasters in Champaign, Illinois, to talk about this summer’s drought.
