OCTOBER 2002: COOLER AND WETTER THAN NORMAL THROUGHOUT MUCH OF THE NATION
Weather patterns help to reduce drought

Last month was the coldest October in the contiguous United States since 1976, according to scientists at the National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center (NCDC) in Asheville, N.C. The unusually cool and wet weather across a large part of the United States in October brought periods of winter-like temperatures and precipitation that led to significant improvements in some drought-affected areas and a reduction in the percent of the nation in moderate to extreme drought.

October 2002 was the 14th coldest and 7th wettest October in the contiguous U.S. since national records began in 1895. The average October temperature in the contiguous U.S. was 52.6 F (11.4 C), more than 2 F below the 1895 – 2001 average. A total of 31 states were significantly cooler than average, and the monthly temperature was much below average in 12 states across the Plains and northern Rockies. The widespread nature of the below-average temperatures contrasts sharply with the past two years. Significantly cooler-than-average temperatures have not occurred in as many states since December 2000. The Southeast and Alaska were the only regions that were warmer than average, as above average statewide temperatures stretched from North Carolina to Louisiana in the Southeast, and the average temperature in Alaska was more than 7 F above the 1971-2000 mean.

The month was also unusually wet for much of the nation. Precipitation was significantly above average in 29 states, and only seven states (California, Nevada, Oregon, Washington, Idaho, Montana and Wyoming) were significantly drier than average. It was the first month since November 2000 in which the contiguous United States was significantly cooler than average and also significantly wetter than average.

Some rainfall was associated with tropical systems. Hurricane Lili made landfall along the Louisiana coast on October 3, with maximum sustained winds near 160 km/hr (~85 knots or 100 mph, category 2 intensity). Rainfall totals were not exceptionally heavy, but precipitation fell in many of the same areas affected by the heavier rains of Tropical Storm Isidore in September. It was the first hurricane to strike the United States since Hurricane Irene in October 1999. Tropical Storm Kyle, which made landfall in South Carolina, and the remnants from Hurricane Kenna, the third-strongest known hurricane to make landfall on the Pacific coast of Mexico, also contributed to the month’s rainfall totals in parts of the South.

The colder than normal temperatures and precipitation in the northern Plains and upper Midwest states led to significant snowfall in some areas. The first heavy snow of the year fell in the upper Midwest on October 20 - 21, with as much as 8 to 10 inches of snow in parts of Minnesota and North Dakota. Measurable snowfall during the latter half of the month occurred as far south as Kansas and New Mexico.

The higher-than-average monthly precipitation totals helped alleviate drought conditions in areas that have been exceptionally dry for much of the past four to five years. More than five inches of rain fell throughout much of western North Carolina and Virginia, bringing relief to areas that were in extreme to exceptional drought in early October. Rainfall, along with cooler than normal temperatures in other areas, also helped reduce the expanse and severity of drought in much of the central and eastern United States.

Abnormally dry conditions became more widespread in parts of the Pacific Northwest, but the percent of the country in moderate to extreme drought fell from 47 percent to 37 percent by the end of the month based on a widely used measure of drought, the Palmer Drought Index*. Approximately 50 percent of the nation was in moderate to extreme drought during the summer months. The greatest expanse of drought during the past century occurred in July 1934, when moderate to extreme drought affected 80 percent of the country.

Globe:
In contrast, the global average temperature was the 4th warmest on record for October. The average global temperature for combined land and ocean surfaces during October 2002 (based on preliminary data) was 0.8 F (0.45 C) above the 1880-2001 long-term mean, the fourth-warmest October since 1880 (the beginning of reliable instrumental records). The warmest October on record occurred in both 1997 and 2001, followed closely by 1998. Although the global ocean-surface temperature tied October 2001 as the second warmest on record, the land-surface temperature average was only the 12th warmest on record (0.7 F less than the record warm month in 1998), as cooler than average temperatures covered large parts of North America, northern Europe, and central Asia.

As has been the case throughout much of 2002, the year-to-date global temperature was again the second warmest on record (1.0 F above average) slightly less than in 1998, the year in which the last El Niño episode ended. El Niño conditions have developed again this year and moderate El Niño conditions are now present in the equatorial Pacific. Although an increase in the strength of this El Niño is possible, it is not expected to compare with the strength of the 1997-98 El Niño episode, according to NOAA’s Climate Prediction Center. (See NOAA El Niño press release at: http://www.noaanews.noaa.gov/stories/s1059.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 Services 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 databases in climatology, oceanography, solid earth geophysics, marine geology and geophysics, solar-terrestrial physics, and paleoclimatology.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate related events and providing environmental stewardship of our nation’s coastal and marine resources.

*The Palmer 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 and extreme.

To learn more about NOAA, please visit:

http://www.noaa.gov.

To learn more about NOAA Satellite and Information Services, please visit:

http://www.nesdis.noaa.gov.

National and global data are online at:

http://lwf.ncdc.noaa.gov/oa/climate/research/2002/oct/oct02.html