Drought - March 2001


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Contents Of This Report:

to go to Top of Page National Overview

On the national scale, severe drought affected about ten percent of the contiguous United States as of the end of March 2001. The total drought area has held steady at about 10 to 15 percent for the last six months (see graph below left). The 2000 drought peaked at about 36% coverage in August, 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 18 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 ten percent during this period (see graph below left).
U.S. Drought and Wet Spell Area, 1996-2001
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U.S. Drought and Wet Spell Area, 1900-2001
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During March 2001, several weather systems brought rain and snow to the U.S. Pacific Northwest, but on average the region had slightly subnormal precipitation resulting in the fifth dry month in a row. Persistent rains brought drought relief to parts of the Southeast, while moisture deficits characterized much of the country from the Ohio Valley to the northern Plains. This pattern is especially 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 reveal increasing stress on vegetation in the central to northern Rockies and adjoining Plains, although this is early in the growing season for the satellite Vegetation Health Index.
  • The Keetch-Byram Drought Index (KBDI) is used by the National Interagency Fire Center to monitor the risk of wildfires. The end-of-March rains in Florida reduced the threat of wildfires there, although the KBDI is still in the moderate risk range in southern Florida. There was an increasing risk of wildfires in the southwestern U.S. as March ended and April began.

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Palmer Drought Indices
The Palmer Z Index shows how monthly moisture conditions depart from normal (short-term drought and wetness). March 2001 was severely dry from the Ohio Valley to the Great Lakes and in parts of the Pacific Northwest and central Plains. Very moist conditions along the Gulf and Atlantic coasts helped reduce drought conditions in parts of those areas. 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. U.S. Animated Palmer Z Index maps
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U.S. Animated Palmer Drought Index maps
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The Palmer Drought Index maps show long-term (cumulative) meteorological drought and wet conditions. Long-term meteorological drought persisted across the Pacific Northwest and in parts of the southern Appalachians and Florida. The PDI maps suggest that the weather pattern giving rise to drought has ended across parts of the Southeast. The animated maps 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.

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 indicates that hydrological drought persisted through the end of March across the Pacific Northwest states, but March rains improved conditions across parts of the Southeast. 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. U.S. Animated Palmer Hydrological Drought Index maps
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to go to Top of Page Regional Drought Watch:

to go to Top of Page Standardized Precipitation Index

The Standardized Precipitation Index (SPI) is another way of measuring drought. The SPI is an index based on the probability of recording a given amount of precipitation, and the probabilities are standardized so that an index of zero indicates the median precipitation amount (half of the historical precipitation amounts are below the median, and half are above the median). The index is negative for drought, and positive for wet conditions. As the dry or wet conditions become more severe, the index becomes more negative or positive. While the Palmer Drought Index is a water balance index that considers water supply (precipitation), demand (evapotranspiration) and loss (runoff), the SPI is a probability index that considers only precipitation.

The seven maps below show the March 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:

  • precipitation in the Pacific Northwest was mid-range for March (but when the unusually warm temperatures are factored in, moisture conditions tilted to the dry side). However, the SPI maps for 2 months out to 24 months show both short-term and long-term dryness across the region;
  • the heavy March rains in the Southeast brought an end to the short-term drought over much of the Deep South region, although drought remained at the long-term (12 to 2month-4) scale, reflecting severe hydrological drought;
  • short-term (1 to month-3) dryness developed from the Ohio Valley to northern Plains. On the longer (9 to 2month-4) time scales, however, unusually wet conditions characterized the northern Plains; and
  • above-normal precipitation in the Northeast during March neutralized the dryness of the previous months.
1-Month SPI Map
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2-Month SPI Map
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3-Month SPI Map
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6-Month SPI Map
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9-Month SPI Map
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12-Month SPI Map
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24-Month SPI Map
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to go to Top of Page Regional Overview

The following table shows the precipitation ranks for the nine standard U.S. regions for March 2001, the three-month period January-March 2001, and the twelve-month period April 2000-March 2001. A rank of 1 is driest and 107 (106 for April-March) is wettest.

Region March 2001 Jan-Mar 2001 Apr 2000-
Mar 2001
Northeast 95 35 80
East North Central 7 35 62
Central 9 24 36
Southeast 102 47 15
West North Central 10 23 32
South 90 94 63
Southwest 71 79 51
Northwest 48 2 2
West 43 53 24

The map to the right shows the departure from normal of the number of days with measurable precipitation for March 2001. The short-term dryness in the Central and North Central regions, as well as Hawaii and parts of Alaska, shows up on this map as significant below-normal (brown) number of precipitation days. Departure from Normal Number of Days with Measureable Precipitation Map, March 2001
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to go to Top of Page Pacific Northwest Dryness

Although the Pacific Northwest received rain and snow from several weather systems during March, the region-averaged precipitation was still below normal, resulting in the fifth dry month in a row (see graph below left). March 2001 ranked as the 48th driest March on record, but the rainy season (November-March, see graph below right) and last 12 months both ranked extremely dry, second only to the record drought of 1976-77. Rivers set new March records for low flows in some Washington valleys, reservoir levels continue to be well below normal, and mountain snowpack continued less than 70% of normal for the end of March in many river basins and near 50% of normal or less in others. The Governors of Washington and Oregon declared drought emergencies in their states. The current (and forecast) low water supplies resulting from the drought are having a major impact on fish, agriculture, and power suppliers in the region. In early April, the Bonneville Power Administration declared a power emergency in the Northwest.
Precipitation Ranks for the
Pacific Northwest, 2000-2001
Period Rank
Apr-Mar 2nd driest
May-Mar 3rd driest
Jun-Mar 2nd driest
Jul-Mar 2nd driest
Aug-Mar 2nd driest
Sep-Mar 3rd driest
Oct-Mar 2nd driest
Nov-Mar 2nd driest
Dec-Mar 2nd driest
Jan-Mar 2nd driest
Feb-Mar 12th driest
Mar 48th driest
Pacific Northwest Region Precipitation Anomalies, January 1998 - March 2001
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Pacific Northwest Region Precipitation, November-March, 1895-2001
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to go to Top of Page Southeast Drought

Heavy rains fell upon much of the U.S. Deep South (AL, FL, GA, LA, MS) during March (see graph below), resulting in the fifth wettest March on record for the region. The precipitation of March 2001 and September and November 2000 has resulted in cumulative wet precipitation ranks for the last seven months (see table to right). Short-term drought conditions have improved considerably, however long-term conditions remain quite dry with many reservoirs in Georgia at very low levels.

Deep South Precipitation Anomalies, Jan 1998 - Mar 2001
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Precipitation Ranks for the Deep South, 2000-2001
Period Rank
Apr-Mar 24th driest
May-Mar 21st driest
Jun-Mar 34th driest
Jul-Mar 35th driest
Aug-Mar 53rd driest
Sep-Mar 37th wettest
Oct-Mar 45th wettest
Nov-Mar 26th wettest
Dec-Mar 50th driest
Jan-Mar 36th wettest
Feb-Mar 23rd wettest
Mar 5th wettest

Florida received abundant rains during March (see graph below), especially during the last week of the month when 8 to 10 inches fell in some localities. The eleventh wettest March on record improved top soil conditions and lessened the threat of wildfires, however long-term conditions remain quite dry with April 2000-March 2001 ranking as the seventh driest such month-12 period on record (see table to right).

Florida Statewide Precipitation Anomalies, Jan 1998 - Mar 2001
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Statewide Precipitation Ranks for Florida, 2000-2001
Period Rank
Apr-Mar 7th driest
May-Mar 7th driest
Jun-Mar 19th driest
Jul-Mar 19th driest
Aug-Mar 25th driest
Sep-Mar 37th driest
Oct-Mar 18th driest
Nov-Mar 33rd driest
Dec-Mar 30th driest
Jan-Mar 38th driest
Feb-Mar 51st wettest
Mar 11th wettest


to go to Top of Page Central, North Central, and Northeast Region Dryness

March 2001 was the tenth driest, or drier, March in the 107-year record for the Central, West North Central, and East North Central U.S. regions (see table above). Five of the last six months were drier than normal for the Central region (see graph below), resulting in the 12th driest October-March on record. For the West North Central and East North Central regions, the March dryness is a short-term phenomenon as the preceding four months (November-February) were near to wetter than normal (see graphs below).

This March was wetter than normal for the Northeast region (see graph below), ranking as the 13th wettest March on record. This region had seen a precipitation deficit during the previous five months. The March surplus brought the October-March 2000-2001 rank to 24th driest. It should also be noted that a significant potential spring water supply remains locked up across much of the region in a deep widespread snow cover.

Central Region Precipitation Anomalies, January 1998 - March 2001
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Northeast Region Precipitation Anomalies, January 1998 - March 2001
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West North Central Region Precipitation Anomalies, January 1998 - March 2001
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East North Central Region Precipitation Anomalies, January 1998 - March 2001
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to go to Top of Page Additional Contacts:

Damage due to the drought has been summarized by NOAA and the Office of Global Programs in the Climatological Impacts section of the Climate Information Project. 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 USDA's National Agricultural Library, the interim National Drought Council, and the NOAA Paleoclimatology Program. The following states have set up web pages detailing their plans to handle drought emergencies:
lorida Panhandle - Georgia - Hawaii - Kentucky - Montana - Nebraska
New Mexico - North Carolina - Oklahoma - South Carolina - Texas - Washington

For additional information on the 2000 wildfire season please see the National Interagency Fire Center web site or the U.S. Forest Service Fire and Aviation web site.

Additional climate monitoring graphics can be found at the Climate Prediction Center's monitoring pages:

Citing This Report

NOAA National Climatic Data Center, State of the Climate: Drought for March 2001, published online April 2001, retrieved on April 24, 2014 from http://www.ncdc.noaa.gov/sotc/drought/2001/3.