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 NCDC / Climate Monitoring / Climate of 2001 / June / Search / Help
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Climate of 2001 - June
U.S. Drought
National Climatic Data Center, 13 July 2001
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Global Analysis / Global Regional / U.S. National / U.S. Regional / U.S. Drought / Extreme Events
Use these links to access detailed analyses of Global and U.S. data.
U.S. Drought Highlights:
- On the national scale, severe drought affected about twelve percent of the contiguous United States as of the end of June 2001
- Allison brought heavy rains to much of the area, but drought lingered across parts of the Southeastern U.S.
- Drought continued across much of the West
- Parts of the southern Plains suffered from hot, dry conditions
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Contents Of This Report:
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 National Overview
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On the national scale,
- severe drought affected about twelve percent of the contiguous United States as of the end of June 2001;
- the total drought area has held steady at about 7 to 15 percent for the last nine months (see graph below left);
- the coverage of the current drought peaked in August 2000 at about 36% of the contiguous U.S., which was as extensive as the major droughts of the last 40 years, but not as large as the "dust bowl" droughts of the 1930's and 1950's;
- on a broad scale, the last two decades were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930's and 1950's were characterized by prolonged periods of extensive droughts with little wetness (see graph below right);
- although different parts of the U.S. have experienced unusually wet conditions during the last 21 months, there continues to be little change in the overall national wetness picture;
- the percentage of the nation severely wet has held steady at about five to eleven percent during this period (see graph below left).
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| Although some areas of the U.S. had well above normal precipitation, many areas were very dry. June averaged above normal when precipitation is integrated across the nation. Eleven of the last 23 months have averaged well below the normal, while only three averaged well above normal (see graph to right). National 2001 precipitation ranks:
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During June 2001, heavy rains from the remnants of Tropical Storm Allison brought relief to parts of the Southeast, however long-term drought persisted across the southern Appalachians, near the confluence of the Ohio and Mississippi rivers, and across most of Florida. Dry conditions continued in the interior Far West and parts of the Northeast, and hot, dry conditions persisted across parts of the southern Plains. This pattern is evident in:
Two other drought-related monitoring tools are the Vegetation Health Index and the Keetch-Byram Drought Index:
- NOAA satellite observations of vegetation health revealed increasing stress on vegetation in parts of the West and southern Plains.
- The Keetch-Byram Drought Index (KBDI) is used by the National Interagency Fire Center to monitor the risk of wildfires. The KBDI showed a drying trend in the southern Plains and parts of the West by the end of June. The Forest Service fire danger analysis indicated a continuing risk of wildfires in the western U.S. during June and the beginning of July.
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Palmer Drought Indices
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| The Palmer Z Index shows how monthly moisture conditions depart from normal (short-term drought and wetness). June 2001 was severely dry across the southern portions of the Pacific Northwest into the Great Basin, west Texas, and parts of the central Plains. Heavy rains from the remnants of Tropical Storm Allison brought relief to the Gulf coast states from eastern Texas to nothern Florida, and along the Atlantic coast from Georgia to southern New England. The animated maps to the right 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.
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The Palmer Drought Index (PDI) maps show long-term (cumulative) meteorological drought and wet conditions. Long-term meteorological drought persisted across much of the West, Maine, Florida, and parts of western and southern Texas. Recent rains have broken up the drought area and decreased its intensity in much of the Southeast. The animated maps to the left show how the geographical pattern of the long-term (meteorological) 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.
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| The Palmer Hydrological Drought Index maps show hydrological (long-term cumulative) drought and wet conditions, which more accurately reflect groundwater conditions, reservoir levels, etc. The PHDI pattern is similar to the PDI pattern and indicates that hydrological drought persisted through the end of June across much of the West, Maine, Florida, and parts of western and southern Texas. Recent rains have broken up the drought area in the Southeast, with severe drought persisting across the southern Appalachians and near the confluence of the Ohio and Mississippi rivers. The animated maps to the right show the geographical pattern of the long-term (hydrological) moisture anomalies for the last 12 months. On these maps, the red shading denotes dry conditions while the green shading indicates wet conditions.
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Regional Drought Watch:
Standardized Precipitation Index
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| The Standardized Precipitation Index (SPI) is another way of measuring drought. The index is negative for drought, and positive for wet conditions. The SPI is a probability index that considers only precipitation, while Palmer's indices, shown in the previous maps, are water balance indices that consider water supply (precipitation), demand (evapotranspiration) and loss (runoff).
The seven maps below show the June 2001 spatial patterns of SPI for seven different periods ranging from one month (short-term conditions) to 24 months (long-term conditions). When taken together, they give a combined geographical and temporal picture of the severity of precipitation anomalies. The maps illustrate, for example:
- the core drought areas in the Northwest, Southeast, and Northeast experienced short-term (month-1) drought relief from heavy rains or at least near-normal rainfall, but these areas still suffer from severe long-term (6- to 2month-4) moisture deficits; and
- short-term moisture deficits were severe across the western half of Texas (1- to month-3s), much of the interior West (month-2s), and parts of the mid-Mississippi valley and Northeast (month-3s).
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Regional Overview
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| The following table shows the precipitation ranks for the nine standard U.S. regions for June 2001, the three-month period April-June 2001, and the twelve-month period July 2000-June 2001. A rank of 1 is driest and 107 (106 for July-June) is wettest.
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| The map to the right shows the departure from normal of the number of days with measurable precipitation for June 2001. The short-term dryness in southwest Alaska, western and central Texas, and the interior Far West shows up on this map as significant below-normal (brown) number of precipitation days. The above-normal precipitation along the northern parts of the Pacific Northwest to the Great Lakes, and along the path of former Tropical Storm Allison in the Southeast, is reflected in a preponderance of above-normal rain days.
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Western U.S. Drought
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Above-normal rainfall occurred along the Canadian border in June, but it brought limited drought relief to the Pacific Northwest. Ranks for 2001:
- a near-normal June regionwide (46th wettest),
- fifth driest January-June,
- third driest month-12 period, July-June (see graph below right).
The Governors of Washington, Oregon, and Idaho have declared drought emergencies in their states. The situation is especially dire in the Klamath Basin of southern Oregon/northern California, where Endangered Species Act rules are denying irrigation water to drought-stricken farmers. Agricultural interests continued to draw irrigation water from low reservoirs in southern Idaho.
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Precipitation Ranks for the
Pacific Northwest, 2000-2001
| Period
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Rank
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| Jul-Jun
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3rd driest
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| Aug-Jun
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4th driest
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| Sep-Jun
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4th driest
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| Oct-Jun
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3rd driest
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| Nov-Jun
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3rd driest
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| Dec-Jun
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4th driest
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| Jan-Jun
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5th driest
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| Feb-Jun
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17th driest
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| Mar-Jun
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47th driest
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| Apr-Jun
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55th driest
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| May-Jun
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28th driest
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| Jun
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46th wettest
(62nd driest)
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| Below-normal rainfall in the West region resulted in the 43rd driest June regionwide. Conditions were unusually hot and dry in the interior West. Nevada had the 17th driest June and third driest May-June (see graph below right) on record. On a local basis, an observer in Reno, Nevada, reported the driest July-June and fourth warmest June. Parched rangeland and low reservoir, lake, and ground water levels are beginning to impact the water supply for some agricultural and ranching interests. The AP reported that the driest wildland conditions in more than half a century have prompted fire officials to impose outdoor restrictions in parts of the West far earlier than usual.
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Southeast and Southern Plains Drought
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| The remnants of Tropical Storm Allison cut a path across the Southeast region during June. The associated heavy rains effectively broke the region's drought area into three parts centered over Florida, the southern Appalachians, and the confluence of the Ohio and Mississippi rivers (see map below right).
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| Some of Allison's rains brought limited drought relief to Florida, primarily the northern areas. Statewide precipitation ranks include:
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- the 34th wettest June,
- the 25th driest April-June, and
- the 13th driest October-June.
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Allison moved across the eastern edge of the South region, dumping copious amounts of rain over eastern Texas to Mississippi. Louisiana experienced the second wettest June on record, with the rain being enough to effectively end the drought there. In spite of the rain, Texas had the 46th driest June statewide. Western and central Texas missed out on the rain (see graph to left). In this region, hot and dry weather (eighth driest June) intensified drought conditions. The AP reported on June 27th that the Rio Grande River, the nation's second-longest river, is now a mere trickle before it gets to the Gulf of Mexico, disappearing about 300 feet short of its destination in a big expanse of sand.
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Northeast Region Dryness
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| Rainfall over much of the Northeast gave the region its 26th wettest June on record. However, drought persisted in some areas:
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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: questions@ncdc.noaa.gov
For further information on the historical climate perspective presented in this report, contact:
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
NCDC / Climate Monitoring / Climate of 2001 / June / Search / Help
http://lwf.ncdc.noaa.gov/oa/climate/research/2001/jun/us_drought.html
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Last Updated Wednesday, 20-Aug-2008 12:22:18 EDT by Richard.Heim@noaa.gov
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