August 14, 2002 — Above-normal temperatures and drier-than-normal conditions occurred across large parts of the United States in July, and led to persistent or worsening drought in many states, according to scientists at NOAA’s National Climatic Data Center in Asheville, N.C. At the end of the month, 49 percent of the contiguous United States was in moderate to extreme drought, based on the Palmer Drought Index, a widely used measure of drought severity.
Drought Index uses numerical values derived from weather and climate data
to classify moisture conditions throughout the contiguous United States
and includes drought categories on a scale from mild to moderate, severe
Precipitation was significantly below average in 27 states in July. New York had its second driest July on record, and it was the third driest July since 1895 in New Hampshire and Colorado. Drier-than-average conditions have persisted in many areas for several seasons—in some parts of the country for several years. The past 12 months were the driest August through July on record in four southeastern states (Georgia, South Carolina, North Carolina and Virginia) and two Rocky Mountain states (Colorado and Wyoming). Three other states (Arizona, Nevada and Delaware) had their second-driest August through July in the 107-year period of record.
Parts of the Southeast and western United States have been in various stages of drought since 1998. Rainfall alleviated drought in West Texas and some areas of the Gulf Coast in July. Though at the end of the month, moderate drought or worse was present in at least part of 37 states as reported by the U.S. Drought Monitor. Based on the Palmer Drought Index, 49 percent of the contiguous United States was affected by moderate to extreme drought at the end of July. Thirty seven percent was affected by severe to extreme drought. Areas of extreme drought stretched from the Southwest to Montana and Nebraska and from Georgia to Virginia. The greatest area of drought coverage to date occurred in July 1934 when moderate to extreme drought covered 80 percent of the contiguous United States.
According to the U.S. Department of Agriculture, more than 75 percent of range and pastures were classified as poor to very poor in five western states (Nebraska, Colorado, California, Wyoming and South Dakota) in early August and more than 50 percent in 13 other states. Wildfires also continued to burn large areas in the western United States. More than 4 million acres had burned throughout the United States by the end of July, with most large wildland fires occurring in the West according to the National Interagency Fire Center. This is slightly more than twice the 1991-2000 average for the same period.
The average temperature for the contiguous United States was 76.4 degrees F (24.7 C) in July (based on preliminary data), 2.2 degrees F greater than the 1895-2001 long-term mean for the month, making it the fifth-warmest July since national records began in 1895. Thirty-nine states were warmer than average, and Utah had its warmest July on record.
The only near-average statewide temperatures in the contiguous United States occurred in southern tier states (Oklahoma, Arizona, Louisiana, Mississippi, Alabama and Florida) and New England (Vermont and Maine). Texas was the only state with a significantly cooler-than-average temperature for the month. Above average rainfall in many areas contributed to the cooler statewide average, and extremely heavy and persistent rains led to severe flooding in parts of central and southern Texas in early July. It was the third-wettest July on record for the state.
As has occurred in previous months, the warmest globally-averaged temperature for the month occurred four years ago during the last El Nino episode. The strength of the 1997-1998 episode contributed to a string of 16 straight months of record-breaking global temperatures in 1997 and 1998. Although global temperature records for the months of January and March were broken in 2002, the average global temperatures since April have been slightly less than the record warm values established four years ago.
Weak to moderate El Niño conditions continue to be present in the equatorial Pacific and are likely to persist through the end of 2002 and into early 2003, according to NOAA’s Climate Prediction Center. (See NOAA El Niño news release at http://www.noaanews.noaa.gov/stories/s959.htm).
NOAA’s National Environmental Satellite, Data, and Information Service (NOAA Satellite and Information Services) is the nation’s primary source of space-based and surface-based meteorological and climate data. NOAA Satellite and Information Service operates the nation's environmental satellites, which are used for weather forecasting, climate monitoring and other environmental applications such as fire detection, ozone monitoring and sea surface temperature measurements.
NOAA Satellite and Information Services also operates three data centers, which house global data bases in climatology, oceanography, solid earth geophysics, marine geology and geophysics, solar-terrestrial physics, and paleoclimatology.