U.S. Drought Highlights:
- On the national scale, severe to extreme drought affected about 9 percent of the contiguous United States as of the end of December 2005.
- Moderate to extreme drought affected about 21 percent of the contiguous U.S.
- The month was much drier than normal across a broad swath of the country from the Southwest to the southern Plains, extending up the Ohio Valley to the southern and eastern Great Lakes. About 19 percent of the contiguous U.S. was very dry (had precipitation in the bottom 10th percentile of the historical record). Parts of southern Florida and the central and northern Rockies also had below-normal precipitation.
- Above-normal precipitation brought relief to much of the drought areas in the Pacific Northwest.
- The December dryness aggravated long-term drought in the southern Plains to Lower Great Lakes and parts of the Ohio Valley (2 to 6 to 9 months). Long-term moisture deficits (last 48 to 60 months) persisted across parts of the West into the northern High Plains and central Plains.
Please Note: The data presented in this drought report are preliminary. Ranks, anomalies, and percent areas may change as more complete data are received and processed.
On the national scale,
- severe to extreme drought affected about 9 percent of the contiguous United States as of the end of December 2005, an increase of about 3 percent compared to last month
- about 21 percent of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of December
- on a broad scale, the previous two decades (1980s and 1990s) were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness
- about 13 percent of the contiguous U.S. fell in the severely to extremely wet categories at the end of December
- a file containing the national monthly percent area severely dry and wet from 1900 to present is available
- historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page in files having names that start with "drd964x" and ending with "txt" (without the quotes).
December 2005 was much drier than normal across a broad swath of the country from the Southwest to the southern Plains, extending up the Ohio Valley to the southern and eastern Great Lakes. About 19 percent of the contiguous U.S. was very dry (had precipitation in the bottom 10th percentile of the historical record). Parts of southern Florida and the central and northern Rockies also had below-normal precipitation.
The December precipitation pattern at the primary stations in Alaska was mainly drier than average in the interior southeast and extreme southwest coastal parts of the state, and wetter than normal in the north and along the remaining coastal areas. Across Hawaii, the precipitation pattern was predominantly drier than average. In Puerto Rico, the precipitation signal was mostly dry, based on National Weather Service radar estimates of precipitation. December streamflow averaged near normal for Puerto Rico but drier than normal for the Hawaiian Islands.
For some Hawaiian stations, this was the third consecutive dry month (Oct, Nov, Dec). According to the early January U.S. Drought Monitor, all of the Hawaiian islands were in abnormally dry (D0) status, with moderate drought (D1) afflicting the western island of Kauai.
The December dryness aggravated long-term drought in the southern Plains to Lower Great Lakes and parts of the Ohio Valley (2 to 6 to 9 months). Long-term moisture deficits (last 48 to 60 months) persisted across parts of the West into the northern High Plains and central Plains.
Some regional highlights:
- Several states had the tenth driest, or drier, month in December and also for multi-month seasons (October-December, July-December, January-December and others). These states include:
- Record dry conditions were reported at stations in Florida and Hawaii and statewide for Arizona and Arkansas in December.
- Arkansas had record dry conditions for several seasons back to February-December, and the second driest year.
- During 2005, the Arklatex (southwestern Arkansas, southeastern Oklahoma, northeastern Texas) experienced the driest year in the 111-year record.
- The prolonged dry spell magnified the threat of wildfires in parts of the southern Plains. Dry, windy, and warmer-than-normal weather contributed to the outbreak of numerous grassfires in Oklahoma, Texas, and New Mexico in December and the beginning of January. According to media reports (New York Times, 1/4), more than half a million acres and more than 500 homes had been burned, with at least 5 people dying due to the winter inferno. Burn bans were in effect across much of Texas.
- In Texas, continuing dry conditions and slowly dropping lake levels prompted the Lower Colorado River Authority to ask Colorado River water users to conserve water voluntarily (Lower Colorado River Authority press release, 12/14). State Extension agents noted that, in some counties soil moisture was very dry with rangelands and pastures in poor condition, stock ponds very low or completely dry, and livestock suffering. In Missouri, the Farm Service Agency reported that low ponds and dry streams were affecting livestock water supply. The ongoing drought put growing pressure on dwindling water supplies in some Arkansas communities. Reservoirs in the Fort Smith area had only a four-month supply of water (KATV, 12/25).
- An examination of USDA snowcourse/snotel station data in Arizona revealed that 31 of 33 sites, or 94% of them, were snow free on January 1, the most snow-free locations in at least the past 40 years.
- End-of-month and month-averaged soil moisture conditions were drier than normal across a broad swath from the southern Plains to the Ohio Valley, a band from the central Plains to the Great Lakes, and parts of the Southwest and Pacific Northwest, based on model computations (CPC-1, CPC-2, MRCC). The models also indicated dry soil moisture conditions in parts of Alaska and Hawaii, and near the surface and at depth from southeast Nebraska to the western Great Lakes.
- Streamflow levels were below seasonal norms across much of the southern Plains to Ohio Valley states, and parts of the central Plains, Lower Great Lakes, Southeast, Southwest, and Hawaii, as computed by models and based on USGS observations.
- Above-normal precipitation in the drought areas of the Pacific Northwest brought improvement to the western U.S. drought percentages. About 14 percent of the western U.S. (Rockies westward) fell in the moderate to extreme drought category (as defined by the Palmer Drought Index) as of the end of December. Aggregated reservoir levels in the West (provided by the USDA) reflected the long-term precipitation deficits in many states.