NOAA's National Centers for Environmental Information
U.S. Drought Highlights:
- On the national scale, severe to extreme drought affected about 4 percent of the contiguous United States as of the end of January 2005.
- Moderate to extreme drought affected about 8 percent of the contiguous U.S.
- January was another dry month across the Pacific Northwest, northern Rockies, northern High Plains, and Southeast. January was also dry across parts of New England.
- Much of the southwestern U.S. drought region was wetter than normal for the fifth month in a row, indicating that the meteorological drought had ended in most areas according to the Palmer Drought Severity Index.
- Long-term moisture deficits (last 24 to 36 to 60 months) persisted across much 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.
National Overview
On the national scale,
- severe to extreme drought affected about 4 percent of the contiguous United States as of the end of January 2005, an increase of about 1 percent compared to last month
- about 8 percent of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of January
- 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 35 percent of the contiguous U.S. fell in the severely to extremely wet categories at the end of January
- 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).
Regional Overview
January was another dry month across the Pacific Northwest, northern Rockies, northern High Plains, and Southeast. January was also dry across parts of New England. But much of the southwestern U.S. drought region was wetter than normal for the fifth month in a row, indicating that the meteorological drought had ended in most areas according to the Palmer Drought Severity Index.
The January precipitation pattern at the primary stations in Alaska was mixed but mostly wetter than normal at the interior stations and drier than normal at the coastal stations. The pattern was also mixed in Hawaii. In Puerto Rico, the south central and northwestern parts of the island were drier than normal, based on National Weather Service radar estimates of precipitation and on Cooperative station precipitation reports for the last 4 weeks. January streamflow averaged near normal for Hawaii and higher than normal for Puerto Rico.
Long-term moisture deficits persisted in many areas. Much of the northern Rockies was dry at the 12 to 24 month timescales. Many Alaska stations, especially in the interior and southern coastal regions, were drier than normal at the 12 month timescale. Severe moisture deficits were evident at the 36 to 60 month timescales across much of the West into the northern High Plains and central Plains. These long-term hydrological drought conditions are reflected in the February 1 United States Drought Monitor map. Below-normal precipitation also persisted at the 60 month timescale across parts of the Southeast and extreme northeastern New England.
Some regional highlights:
- Oregon had the ninth driest January and November-January in the 111-year record
- End-of-month and monthly averaged soil moisture conditions were drier than normal across parts of the northern Rockies and central and northern Plains, the Pacific Northwest, and the coastal Southeast, based on model computations (CPC-1, CPC-2, MRCC). The models also indicated dry soil moisture conditions in eastern Alaska, Hawaii, and near the surface and at depth across parts of the central Plains to the Great Lakes.
- Streamflow levels were below seasonal norms across a few parts of the Pacific Northwest, central and northern Rockies and Great Plains, and coastal Southeast, both as computed by models and based on USGS observations.
- Snow water content of the western mountain snowpack contrasted sharply from south to north. Basin-averaged end-of-January snowpacks in parts of Arizona, Nevada, central California and Utah were above average, while snowpacks in Oregon, Washington, Idaho, Montana and the east slopes of the northern Rockies were significantly below average. This pattern, which is also apparent in basin-averaged water-year-to-date precipitation anomalies, reflected a southerly track of winter storms across the region for the last five months. As reported by the USDA, several individual stations in the remote high altitude SNOTEL network set new record lows (in the north) and highs (in the south) for both snow water content and water-year-to-date accumulated precipitation.
- Reservoir levels in most of the western states continued well below seasonal normals. Although long-term (out to 5-years) moisture conditions remained dry across much of the West, drought conditions improved during the last 5 months. The percent area of the western U.S. (Rockies westward) experiencing moderate to extreme drought (as defined by the Palmer Drought Index) decreased from about 67% in July 2004 to under 10% by December. Intensification of drought in the Pacific Northwest (November, January) resulted in an expansion of the western drought area to about 18% by the end of January.
