|
 NCDC / Climate Monitoring / Climate of 2001 / August / Search / Help
|
Climate of 2001 - August
U.S. Regional Drought Watch
National Climatic Data Center, 17 September 2001
|
|
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.
 Regional Overview
|
A potent Pacific storm system brought heavy rainfall to coastal Washington and Oregon in the middle of the month, however most of the western U.S. suffered from hot and dry weather during August, resulting in a continuation of drought conditions and a flare-up of wildfires in several states. A series of cold fronts brought drought relief to parts of the Great Lakes and Northeast, but the month still averaged hot and dry in many areas, continuing long-term moisture deficits there. In spite of heavy rains from Tropical Storm Barry early in the month, August precipitation totals were below normal across sections of Florida to the Carolinas, where patchy long-term drought persisted. Tropical moisture brought copious rainfall to parts of the southern Plains, bringing limited drought relief to parts of Texas, but severe drought continued across parts of Oklahoma and Arkansas. The drought signal was mixed in Alaska and Hawaii, with some stations having below-normal precipitation during August and others reporting a wetter-than-normal month. August was severely dry across parts of the northern Plains, interrupting a long-term wet spell in the region. This overall 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 from late August revealed continued stress on vegetation in parts of the West, southern Plains, Northeast, and Great Lakes.
- The Keetch-Byram Drought Index (KBDI) is used by the National Interagency Fire Center to monitor the risk of wildfires. The late August KBDI showed dry conditions in the southern Plains, parts of the West, and extreme Southeast. The Forest Service fire danger analysis indicated a continuing risk of wildfires in the western U.S. by the end of August.
|
Western U.S. Drought |
Rainfall across much of the western U.S. was well below normal during August as evidenced by the station precipitation reports, statewide precipitation ranks, and Palmer Z Index. Montana had the third driest August and Idaho the fifth driest August in the 107-year record, based on preliminary reports. Highlights:
- The combination of hot, dry, windy conditions and high-altitude dry thunderstorms sparked thousands of new wildfires. During the first 20 days of August, about 1.23 million acres were blackened in the Great Basin, Pacific Northwest, and northern California, increasing the national year-to-date total to 2.83 million acres (103% of the 10-year average).
- Stream flows and lakes continued to decline and, by mid-month, were generally at much below normal or near-record low levels.
- Conditions at over half of the pastures and ranges in California, Washington, Montana, and Idaho were rated at mid-August as very poor to poor by the USDA's National Agricultural Statistics Service.
- Long-term moisture deficits remained severe, especially in the northwestern quarter of the country.
|
The summer is normally the dry season for the Pacific Northwest. Regional ranks for 2001:
- a slightly drier-than-normal August regionwide (49th driest),
- 45th wettest summer (June-August),
- third or fourth driest rank for the 8-month through 12-month periods (see table to right).
Declared drought emergencies continued in three western states (Washington, Oregon, and Idaho). Record or near-record low streamflows and reservoirs were stressing agricultural and other interests. In Idaho, groundwater users and surface irrigators reached agreement on water use before intervention by the Idaho Department of Water Resources was required.
|
|
| August rainfall averaged across the West region was below normal (see graph below left). Since the summer is the dry season for this region, the actual rainfall amounts were small. However, long-term drought conditions remain severe. August rainfall was near normal for the Southwest region (see graph below right). Some 2001 ranks for the ...
|
|
... West region:
|
... Southwest region:
|
Southeast and Great Plains Drought |
| Heavy rains improved drought conditions over parts of the southern Plains and Gulf coastal states during August. Above-normal rain fell across much of Texas, although drought continued over parts of Oklahoma and Arkansas (see maps below). Rainfall averaged across the South region was above normal for August.
|
| Heavy rains from Tropical Storm Barry brought drought relief to Florida early in the month, but total monthly precipitation for August was still below normal from sections of Florida to the Carolinas. Statewide precipitation ranks for August included 11th driest for South Carolina, 20th driest for Georgia, and 22nd driest for Florida.
Regionwide, the Southeast averaged below normal for August (see graph below left), with a rank of 34th driest. This year marked the fifth consecutive August with below average precipitation. With near to much above normal rainfall during June and July, summer (June-August) 2001 ranked 35th wettest, which is a break from the pattern of summer dryness of recent years. However, the region has suffered from severe drought for much of the last three and a half years (see graph below left). September 2000-August 2001 ranked as the 36th driest such period and marked the third consecutive September-August period with well below average precipitation (see graph below right).
|
|
Two-year precipitation deficits remain severe in four areas: Florida, the southern Appalachians, parts of Texas, and the confluence of the Ohio and Mississippi rivers (see map to right). Rains from Tropical Storm Barry and earlier summer systems have helped recharge Florida aquifers, rivers, and lakes, but dryness returned later in the month. A few wells were near or at record low levels in Dade County, and Tampa experienced a 14-day dry spell which was the longest such dry stretch during August on record. Although Lake Okeechobee's level rose in response to the rains, it was still 2.7 feet below the 1979-1995 average in mid-August, or about the same level as August 2000. By the end of August in southern Texas, the two lakes on the Rio Grande that provide much of the municipal and irrigation water for the four counties at the southern tip of Texas were below 25% of conservation capacity, a threshold at which mandatory and/or voluntary conservation measures kick in for many communities and water districts.
|
larger image
|
| An unusually dry August in the northern Great Plains (see graph below left) was a departure from the persistently wet conditions that have characterized this region for much of the last twelve months. The West North Central region had the third driest August in the 107-year record, contrasting with the 23rd wettest summer (June-August) and 36th wettest September-August. On a statewide basis (see map below right), South Dakota had the driest August on record, Montana third driest, and North Dakota 12th driest. In spite of the dry August conditions, long-term conditions remained very moist over much of the northern Plains.
|
Northeast and Great Lakes Region Drought |
August 2001 was the second consecutive dry month over much of the Northeast and Great Lakes (East North Central) regions (see graphs below). Conditions were especially severe in parts of the Northeast. Some highlights:
- 33rd driest August for the Northeast and 45th driest August for the East North Central regions;
- 12th driest August for New Hampshire and 14th driest August for Maine;
- eighth driest April-August, 12th driest January-August, and 15th driest September-August for the Northeast region;
- Pennsylvania expanded their drought watch to include 45 counties in which the residents were asked to voluntarily cut back on water use due to low groundwater supplies;
- groundwater supplies were impacted by the drought in parts of Vermont, requiring the drilling of new wells in places.
|
Additional Contacts: |
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: ncdc.info@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 / August / Search / Help
http://lwf.ncdc.noaa.gov/oa/climate/research/2001/aug/drought-regional-overview.html
Downloaded Tuesday, 07-Oct-2008 01:27:42 EDT
Last Updated Tuesday, 12-Jul-2005 10:52:30 EDT by Richard.Heim@noaa.gov
Please see the NCDC Contact Page if you have questions or comments.
|
