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Published February 23, 2011
U.S. Drought Monitor(through 2/15/11)
Data Source(s): U.S. Department of Agriculture, National Drought Mitigation Center, National Oceanic and Atmospheric Administration
There has been little change in the extent of drought conditions across the western U.S. over the past 30 days. Overall, only 27 percent of the 11 western U.S. states, excluding Hawaii and Alaska, are observing abnormally dry conditions or worse; only about 9 and 4 percent is classified with moderate and severe drought, respectively. The majority of the area classified with abnormally dry conditions or worse is located in Arizona and New Mexico, where La Niña-induced dry conditions have reigned. A persistent northerly winter storm track has caused dry conditions in the Southwest, but also has contributed to above-average precipitation in the Pacific Northwest and much of the northern and central Rocky Mountains. A small area of abnormally dry conditions has developed over northern California, where below-average precipitation has fallen over the past month. Most of California and Utah and all of Nevada are drought free, in part because very intense storms walloped these regions in December. In parts of Southern California and Nevada, these storms alone delivered nearly a year’s worth of precipitation.
The U.S. Drought Monitor is released weekly (every Thursday) and represents data collected through the previous Tuesday. The inset (lower left) shows the western United States from the previous month’s map.
The U.S. Drought Monitor maps are based on expert assessment of variables including (but not limited to) the Palmer Drought Severity Index, soil moisture, streamflow, precipitation, and measures of vegetation stress, as well as reports of drought impacts. It is a joint effort of several agencies; the author of this monitor is Matthew Rosencrans, NOAA/NWS/NCEP/CPC.
The best way to monitor drought trends is to pay a weekly visit to the U.S. Drought Monitor website:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubious, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer