 NCDC / Climate Mon. /
Climate-2007 / Apr / U.S. Drought / Help
Climate of 2007 - April
U.S. Drought Watch
National Climatic Data Center, 15 May 2007
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Global Analysis /
Global Hazards /
United States /
Extremes
Use these links to access detailed analyses of Global and U.S. data.
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Contents Of This Report:
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 National Overview
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- Based on the Palmer Drought Index,
severe to extreme drought affected about 18 percent of the contiguous United States as of the end of April 2007, about the same as last month.
By contrast, about 11 percent of the contiguous U.S. fell in the severely to extremely wet categories.
- About 30 percent of the contiguous U.S. fell in the
moderate to extreme drought categories (based on the Palmer Drought Index) at the end of April .
- 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 (
moderate to extreme drought,
severe to extreme drought).
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- A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
- 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).
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Detailed Drought Discussion
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At the end of April extreme drought was concentrated in the Southwest, the western High Plains, northern Minnesota, and the Southeast. Drought and abnormal dryness covered a broad swath from the Southwest through the northwestern Plains into the upper Midwest, as well as another area in most of the Southeast (May 1 Drought Monitor). Conditions in southern California and southwestern Arizona continued to deteriorate.
Storm systems throughout the month brought much needed precipitation to the Plains and upper Midwest and eliminated the drought conditions that had persisted for many months.
In the Southwest, Southeast and upper Midwest, soil moisture was low. At the end of the month vegetation was stressed over a large part of the country. Streamflow was low in a wide area of the Southeast.
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Fires consumed over 50,000 acres in the Everglades in Florida in April. Low water levels in southern Florida delayed construction activities, caused increased silt in the intake of water supply systems, affected sales of landscape and horticulture materials, and led to more severe water usage restrictions. Alligators are being seen more frequently as they move in search of wetter habitat.
In central California water deliveries are being postponed, and farmers were affected by poor pastures and water shortages. Governor Arnold Schwarzenegger warned the state to plan for drought because the winter was extraordinarily dry. He also urged residents to conserve water.
Twenty-one counties in southeastern Georgia are in a state of emergency due to extreme fire danger from drought. A wildfire in the southeast part of the state was the largest in the history of Georgia.
Large ships on Lake Superior carried lighter loads to avoid striking the bottom of the lake. Recreational boats and sailboats had difficulty on Lake Superior because of low water levels. The water became so shallow that rowers in the Duluth, Minnesota Rowing Club could touch the bottom with their oars.
Impacts in drought-stricken areas have been collected and summarized by county at the National Drought Mitigation Center's Drought Impact Reporter.
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State/Regional/National Moisture Status
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Pre-Instrumental Perspective
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There is no April 2007 Paleoclimatic Perspective
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Drought Indicators
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The following indicators illustrate the drought conditions this month:
- Palmer Drought Indices,
- Standardized Precipitation Index,
- long-term (36 to 60 month) percent of normal precipitation maps,
- airport station percent of normal precipitation maps,
- statewide precipitation rank maps,
- Cooperative station percent of normal precipitation maps,
- percent of average maps for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center
- snow course snowpack observations in the western mountains provided by the USDA NRCS,
- satellite-based observations of vegetative health,
- National Weather Service model calculations of
- National Weather Service model calculations of soil moisture using the Leaky Bucket Model,
- Midwest Regional Climate Center model calculations of soil moisture,
- streamflow maps maintained by the USGS.
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Additional Contacts:
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- For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:
Climate Services Division
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4876
phone: 828-271-4800
email: ncdc.info@noaa.gov
- For further information on the historical climate perspective presented in this report, contact:
Ned Guttman
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Ned.Guttman@noaa.gov
-or-
Richard Heim
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Richard.Heim@noaa.gov
-or-
Jay Lawrimore
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Jay.Lawrimore@noaa.gov
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NCDC / Climate Mon. /
Climate-2007 / Apr / U.S. Drought / Help
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