Fri Dec 21, 2012, 09:15 AM
hatrack (39,885 posts)
CPC - Drought Expected To Continue, Intensify Into Spring 2013
The Climate Prediction Center forecasts drought conditions to either persist or intensify in the Plains states throughout the winter, for two reasons. First, the winter months are traditionally a time of little precipitation so the effects of heavy rainfall events would be less pronounced than they otherwise would be. Second, the long-term impacts of the drought have begun affecting critical natural water systems, which take much longer to restore.
Moderate rains and snowfall, like those expected in the next two weeks, would be unlikely to provide much relief. The Palmer Hydrological Drought Index measures the severity of long-term water-system impacts, such as reservoir levels and groundwater levels, which take longer to develop and longer to recover. According to the NOAA’s latest State of the Climate report, released last week, recent short-term drought conditions have exacerbated hydrologic droughts across the nation, meaning it will take more rainfall to repair the damage that has been done.
"When we do have precipitation, very little will go to runoff," said Brian Fuchs, climatologist at the University of Nebraska, in a press release. "Those soils are going to act as a big sponge. They're just going to take in a lot of the moisture. We'll continue to see problems of stock ponds, smaller lakes and streams dropping. The hydrologic drought hasn't reared its head, but it's there, as we are seeing more water systems under stress." Major rivers and freshwater bodies are already dropping to near record-low levels. The Mississippi River, which may hit a record low level at some locations during the next few weeks, is already facing shipping closures that threaten the $7 billion in commerce that travel on its waters annually.
Part of what makes long-term droughts so difficult to recover from is their ability to suppress new rainfall, since by drying the soils, they begin to alter the surrounding climate. "In Nebraska and the central Plains, we've started seeing the drought feeding off itself, with the dry soils and dry air not allowing precipitation events to develop as usual," Fuchs said. "With the lack of moisture, we're more like a desert environment. It warms up fairly quickly during the day, but drops quickly at night."
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