U.S. Drought Monitor(data through 5/14/13)
Data Source(s): U.S. Department of Agriculture; National Drought Mitigation Center; National Oceanic and Atmospheric Administration
A relatively dry and warm weather pattern set up across much of the western U.S. in the last month, leading to an expansion of short-term drought conditions in some areas. At least abnormally dry conditions cover more than 85 percent of the West, an increase from 80 percent reported last month, according to the May 14 update of the U.S. Drought Monitor (Figure 3). California saw some of the largest changes in drought conditions in the past 30 days, with moderate and severe drought expanding to cover the entire state. The February–April period for California was the driest on record. Abnormally dry conditions also developed across Oregon and Idaho, replacing drought-free conditions reported there one month ago. The most extreme drought conditions continue to be in New Mexico, where exceptional drought expanded dramatically. The winter storm season is winding down and will leave little chance for improvement in drought conditions across much of the West in coming months. However, the summer monsoon, which typically starts in early July and continues through September, may bring some welcome relief to parts of the Southwest.
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.