News•December 20, 2012

Drought to Last Into 2013; Impacts Expected to Intensify

After another week of below-average rainfall and warm temperatures in the Midwest and Great Plains, it is all but guaranteed that this year will end with more than half of the area in the lower 48 states still under drought conditions. And as the drought is poised to enter 2013, climatologists expect its impacts to worsen as it lasts through the winter.

Source: Drought Monitor/UNL

The total extent of the current U.S. drought, which developed rapidly and unexpectedly last spring, shrank a little this week, according to the latest U.S. Drought Monitor, a combined measure of short-and long-term drought indicators. The percent of land area in the lower 48 states classified under moderate-to-exceptional drought receded slightly, from 61.87 to 61.79 percent. However, impacts in the hardest-hit areas have expanded, with the area under extreme or exceptional drought climbing to 21.67 percent from 21.07.

Rains over Arizona and the Gulf Coast eased drought conditions somewhat in those regions. In parts of Nevada, Southern California and Central Nevada, a wet week brought improvement to some of the moderate and severe drought areas. Similar improvements were observed in Alabama, Eastern Texas, and Louisiana.

Drought conditions deteriorated slightly in Wyoming, Georgia the Carolinas, and parts of Texas, all of which saw slight shifts into more intense drought classifications. The most devastating impacts continue to be in the states between the Rocky Mountains and the Mississippi River. For the second week in a row, 100 percent of the land area in Nebraska and Kansas were classified as under “severe” drought or worse.

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.

Source: CPC/NOAA

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.”

The 2012 drought has already been one of the costliest natural disasters of the year. Agricultural yields, particularly for corn, soybeans and wheat, fell far below what was expected, and have resulted in significant losses. The National Climatic Data Center will release an official estimate of its cost in mid-2013, but has already recorded it as a “billion-dollar climate disaster.” Current estimates range from $36 billion to more than $100 billion, and it could prove to be more expensive than Hurricane Sandy.