Drought expanded and intensified in the week that ended Nov. 20, according to the U.S. Drought Monitor map. Until this week, the Drought of 2012 had been steadily if incrementally receding since its peak on Sept. 25.
Statistics released with the U.S. Drought Monitor map showed increases in all categories of drought. The map showed 50.30 percent of the country in moderate drought or worse, compared with 49.24 percent the week before; 31.67 percent in severe drought or worse, compared with 30.10 percent a week earlier; 15.93 percent in extreme drought or worse, compared with 15.31 percent the week before; and 5.23 percent in exceptional drought, up from 5.02 percent the preceding week.
It got worse in parts of Virginia, Louisiana, Kansas, Texas, Oklahoma, California, Nevada and New Mexico. Exceptional drought, the worst category, crept into southern Kansas.
There was no change to the drought centered over Nebraska, but the persistent drought in the northern Plains was taking a toll on the winter wheat crop. “Poor crop conditions on the Plains are driving the overall U.S. winter wheat crop to its lowest condition ratings since records of this type began in 1986,” said Brad Rippey, U.S. Department of Agriculture meteorologist. “Previous years when wheat struggled in the autumn included 1999, 2001, 2003, and 2007.”
Drought this year has covered the largest area of the United States recorded so far in the 13-year history of the U.S. Drought Monitor, peaking on Sept. 25 at 54.77 percent of the contiguous United States in moderate drought or worse. The Palmer Drought Severity Index, which can be computed for a longer period of record, shows the extent of drought was larger in the 1950s and the 1930s.
Drought Monitor authors synthesize many drought indicators into a single map that identifies areas of the country that are abnormally dry (D0), in moderate drought (D1), in severe drought (D2), extreme drought (D3) and exceptional drought (D4).
The U.S. Drought Monitor map is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture, and about 350 drought observers across the country. It is normally released each Thursday based on data through the previous Tuesday, but this week it was released on Wednesday because Thursday is the Thanksgiving holiday.
Statistics for the percent area in each category of drought are automatically added to the U.S. Drought Monitor website each week for the entire country and Puerto Rico, for the 48 contiguous states, for each climate region, and for individual states: http://drought.unl.edu/MonitoringTools/USDroughtMonitor/DroughtMonitorTips.aspx
The National Climatic Data Center maintains drought data based on the Palmer Drought Severity Index, calculated to the beginning of the historic record. The percent area of the U.S. in moderate to extreme drought since 1895 is online: http://www1.ncdc.noaa.gov/pub/data/cmb/sotc/drought/2012/10/uspctarea-wetdry-mod.txt
U.S. Drought Monitor map and narrative summary: http://droughtmonitor.unl.edu
National Climatic Data Center’s State of the Climate Drought Summary: http://www.ncdc.noaa.gov/sotc/drought/
Seasonal Drought Outlook: http://www.cpc.ncep.noaa.gov/products/expert_assessment/seasonal_drought.html
U.S. Department of Agriculture’s running tally of farm and food impacts from the Drought of 2012: http://www.ers.usda.gov/newsroom/us-drought-2012-farm-and-food-impacts.aspx
-- Kelly Helm Smith, National Drought Mitigation Center