NOAA's National Centers for Environmental Information
Contents of This Report:
National Drought
Long-term drought areal coverage (as measured by the Palmer Drought Index) increased when compared to April, with about 23% of the country in severe to extreme drought during May. Hardest hit areas included portions of the southeast, Louisiana, central and west Texas, Arizona, and portions of the primary corn and soybean agricultural belt.
Although severe to extreme drought persists in many parts of the U.S., several droughts in the past hundred years have covered a much larger area for a much longer time (see graph below right). The May 2000 drought is about 60% of the magnitude of the 1988 drought at its peak. The percent area of the country experiencing severe to extreme wetness dropped steadily from 23% in August 1999 to roughly four percent at the end of May.
 larger image |
 larger image |
Crop impact information can be found at the USDA NASS (National Agricultural Statistics Service) and Weekly Weather and Crop Bulletin pages. Drought statements by local National Weather Service Offices can be found at the NWS Hydrologic Information Center. Drought threat assessments and other information can be found at NOAA's Drought Information Center. Additional drought information can be found at the National Drought Mitigation Center. The following states, among others, have web pages detailing their drought conditions:
Palmer Drought Indices
The Palmer Z Index shows how monthly moisture conditions depart from normal (short-term drought and wetness). The May 2000 pattern shows areas of extremely dry conditions located in the southeast from central South Carolina through Florida and west through most of Alabama and southeastern Louisiana. Another area of extremely dry conditions is located from central Texas westward through southeastern California. Yet another less organized area of extremely dry conditions is noted in the central Plains over portions of eastern Colorado, western Kansas, northwestern Missouri, southwestern Iowa, and southern Nebraska. Moisture deficits were also noted in the upper peninsula of Michigan. Unusually wet conditions were centered over the western and central Great Lakes states and portions of the Northeast.
 larger animated image |
The animated maps show the geographical pattern of the moisture anomalies for the last 12 months. On these maps, the red shading denotes dry conditions while the green shading indicates wet conditions. |
The Palmer Drought Index maps show long-term (cumulative) drought and wet spell conditions. By the end of May 2000, long-term drought continued across the southern tier states from southern California to the Southeast. Long-term drought conditions were also noted in portions of the mid Mississippi Valley, southern Great Lakes and central Appalachians. Patchy long-term wet conditions were found in New England and the northern Plains.
 larger animated image |
The animated maps show how the geographical pattern of the long-term moisture conditions has changed over the last 12 months. On these maps, the red shading denotes drought conditions while the green shading indicates wet conditions. |
The Palmer Crop Moisture Index is computed on a weekly basis by the National Weather Service's Climate Prediction Center and is useful for following the impact of precipitation anomalies on agriculture. The animated Crop Moisture Index maps show the weekly change in topsoil moisture conditions for 2000 from March 4th through June 3rd, the growing season to date.
 larger animated image |
The animated maps show how the geographical pattern of the long-term moisture conditions has changed over the last three months. On these maps, the red shading denotes dry conditions while the green shading indicates wet conditions. |
Regional Drought Watch
| Regions Discussed: | 
|
Southeast Region Precipitation Deficit
| Eighteen of the last 29 months have averaged drier than normal across the Southeast region. The last seven months have been especially dry, with 2000 having the third driest January-May since 1895. The seven-month period, November 1999-May 2000 was the tenth driest such period in the last 105 years. |  larger image |
The Palmer Drought Index (PDI) has been used for U.S. drought monitoring for the last 30 years. It is based on a water budget model that incorporates the balance between water supply (i.e., precipitation), soil moisture, runoff, and water demand (computed from estimates for evaporation and transpiration). The PDI is a long-term drought index which incorporates the current conditions (i.e., for the current month) and the past conditions (the preceding several months). The PDI is useful for showing how the current drought compares to past droughts.
 larger image |
The present drought situation in the Southeast began quickly and is approaching, in both magnitude and duration, the drought situation noted in the early 1980's. Through the end of May, the areas of greatest impact were in southern Alabama and from south-central South Carolina, through central Florida. It is readily noted that the longest drought on record for the Southeast occurred in the 1950's. |
| One of the cities most impacted by drought in the Southeast region is the Tampa Bay area of Florida. January-May 2000 was the second driest such period on record for the Tampa Bay region and May 2000 was the driest such month since records began for the region in 1890. The last seven consecutive months have averaged below normal for precipitation including only 0.02 inches of rainfall for all of May. |  larger image |
South Region Precipitation Deficit
| Fifteen of the last 29 months have averaged drier than normal across the South region. The last eleven months have been especially dry, with 2000 having the 25th driest January-May since 1895. The eleven-month period, July 1999-May 2000 was the third driest such period in the last 105 years. |  larger image |
 larger image |
As with the Southeast Region, the present drought situation in the South began quickly and presently surpasses in magnitude any drought situation since the late 1960's. Through the end of May, the areas of greatest impact within the South region include southern Mississippi, southern Louisiana, and central and western Texas. It is readily noted that the longest and most severe drought on record for the South occurred in the 1950's. |
| One of the cities most impacted by drought in the South region is El Paso, Texas. Precipitation has been below normal for seven of the last twelve months, and below normal for 14 of the last 20 months. No precipitation was measured in January 2000 and only a trace of precipitation was noted during May 2000. |  larger image |
Southwest Region Precipitation Deficit
| Sixteen of the last 29 months have averaged drier than normal across the Southwest region. The last eight months have been especially dry, going on record as the third driest October-May in the last 105 years. |  larger image |
 larger image |
The present drought situation in the Southwest region also began rather abruptly and presently ranks as the second worst drought, in terms of magnitude, since the early 1960's. However, longevity remains to be seen. Through the end of May 2000, the area of greatest impact included most of Arizona, western Utah, as well as central and southern New Mexico. |
| One of the cities most impacted by drought in the Southwest region is Tucson, Arizona. Through the end of May, Tucson had received only 22% of the normal year-to-date rainfall and the water year-to-date, October 1999-May 2000, was the driest such period on record. |  larger image |
Current data are based on preliminary reports from River Forecast Center stations and First and Second Order airport stations obtained from the National Weather Service (NWS) Climate Prediction Center and real time Global Telecommunications System (GTS) monthly CLIMAT summaries. THE CURRENT DATA SHOULD BE USED WITH CAUTION. These preliminary data are useful for estimating how current anomalies compare to the historical record, however the actual values and rankings for the current year may change as the final data arrive at NCDC and are processed.
The following NCDC datasets are used for the historical U.S. data: the climate division drought database (TD-9640), and the hurricane datasets (TD-9636 and TD-9697). It should be noted that the climate division drought database consists of monthly data for 344 climate divisions in the contiguous United States. These divisional values are calculated from the 6000+ station Cooperative Observer network.