August 1, 2011

US Experiences ‘Exceptional Drought’ In July

Nearly 12 percent of the contiguous US land area experienced record drought in July, reaching the highest levels in the history of the US Drought Monitor, according to the National Drought Mitigation Center (NDMC) at the University of Nebraska, Lincoln (UNL).

The drought fell into the "exceptional" classification during the month of July, peaking at 11.96 percent on 12 July. That level had never been recorded in the 12-year history of the drought monitor, said Brian Fuchs, UNL assistant geoscientist and climatologist at NDMC.

The US Drought Monitor uses a ranking system that ranges from D0 (abnormal dryness) to D4 (exceptional drought). The impact of exceptional drought includes widespread crop loss, and shortage of water reservoirs, steams and wells, creating water emergencies.

Currently, as much as 18 percent of the contiguous US is classified as D3 (extreme drought) or D4, according to Fuchs. Much of the drought is contained throughout the south, especially in Texas, where the entire state is experiencing drought -- as much as 75 percent of the state in exceptional drought classification.

NDMC's most recent monitor report, released last week, indicated that 59 percent of the US was drought-free, while 41 percent experienced some form of drought. A report two weeks ago showed that the country was 64 percent drought-free.

New Mexico, Louisiana and Oklahoma are all experiencing some form of drought in 100 percent of the land area. New Mexico is 48 percent exceptional, Louisiana 33 percent exceptional, and Oklahoma 52 percent exceptional, or D4.

South Carolina, Georgia, Arkansas and Florida are all experiencing some form of drought in more than 88 percent of their land areas, with Georgia experiencing high levels of exceptional drought -- 68 percent.

NDMC thinks there should be some improvement in some affected areas in the next couple of weeks. The wake of Tropical Storm Don should result in rainfall in the central and western Gulf Coast states. However, the amount of relief these areas will feel depends on the storm's intensity, as well as its track and speed.

"Whenever there is a lot of moisture in a short period of time, the potential exists for rapid improvement," said Fuchs. "But while that possibility exists, it won't necessarily mean the end of drought in those areas. It will likely only improve by one drought category for those areas not impacted by any tropical storms or where drought related impacts improve."

The drought monitor uses numeric measures of drought combined with experts' best judgments to come up with their findings. The report is produced by the NDMC, the US Department of Agriculture, and the National Oceanic and Atmospheric Administration. The report incorporates reviews from more than 300 climatologists, extension agents and other weather observers across the country.

The NDMC updates and revises the map each week based on rain, snow and other events. Observer reports, wildlife and other indicators also factor in on the weekly report.


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