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Climate of 2003
September in Historical Perspective
National Climatic Data Center
15 October 2003
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Contents of this Report:
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Major Highlights
NOAA REPORTS COOL START TO AUTUMN IN PARTS OF THE U.S.
GLOBAL TEMPERATURE WARMEST ON RECORD FOR SEPTEMBER
Many states from the Central Plains to the Southeast were cooler than average while some western states had near record warmth in September 2003, according to scientists at the National Oceanic and Atmospheric Administration�s (NOAA) National Climatic Data Center (NCDC) in Asheville, N.C. The mid-Atlantic and Northeast were unusually wet, but precipitation was near average for the nation as a whole. The global average temperature was warmest on record for the month of September.
NOAA scientists report that the average temperature for the contiguous United States in September (based on preliminary data) was 65.4°F (18.6°C), which was 0.1°F (0.06°C) below the 1895-2003 mean. The mean temperature in four states (Maine, Vermont, Nevada and California) was much above average, while fourteen others were significantly warmer than average. Conversely, significantly cooler than average temperatures occurred in seventeen states, primarily in the Central and Southern Plains, the central Mississippi Valley, the Ohio Valley and parts of the Southeast. The average September temperature in Alaska was 1.1°F (0.6°C) below the 1971-2000 mean.
Precipitation for the contiguous US as a whole was near average, but the western US was drier than average while much wetter than average conditions stretched from the Mississippi Valley to the mid-Atlantic and Northeast. Much of the monthly rainfall in states from North Carolina to Maine was attributable to Hurricane Isabel, which made landfall along the Outer Banks of North Carolina on September 18th as a minimal category 2 storm on the Saffir-Simpson scale, with sustained winds near 100 mph. Precipitation totals were lower and flooding much less extensive than that produced by Hurricane Floyd in 1999. Precipitation in parts of eastern North Carolina approached 20 inches as Hurricane Floyd moved inland on September 16, 1999. Less than half that amount was measured from Isabel, but the combination of wet soil, resulting from many months of above average precipitation, and strong winds from Hurricane Isabel, led to downed trees and power outages for millions of people.
Hurricane Isabel moved over areas that have been persistently wet for the last 12 months. Virginia had its wettest October-September on record with rainfall exceeding the next wettest October-September by a remarkable 10 inches (254 mm). More than 65 inches (1650 mm) fell from October 2002 to September 2003. This rainfall total is also remarkable for the fact that it is over twice the amount that fell during the previous 12-month period (32.1 inches from October 2001 through September 2002), the 3rd driest October-September period on record. Three other states had their wettest such 12 months on record (Delaware, Maryland and North Carolina) and the Southeast as a whole was the wettest in 108 years of record keeping for that 12-month period.
In contrast to the record and near-record rainfall in the East, drought continued to affect many parts of the West. While some improvement occurred early in 2003, drought worsened through the summer and early fall of 2003. At the end of September 2003, 76% of the western United States was in moderate to extreme drought, based on a widely used measure of drought, the Palmer Drought Index, and drought also persisted in the Plains and Upper Midwest. The most extensive drought on record for the West occurred in July 1934, when 97% of the region was in moderate to extreme drought.
Globe:
The average global surface temperature for combined land and ocean surfaces during September 2003 (based on preliminary data) was 1.0°F (0.6°C) above the 1880-2002 long-term mean, the warmest September since 1880 (the beginning of reliable instrumental records). The 2nd and 3rd warmest on record occurred in 1997 and 1998, respectively. Since 1900, global surface temperatures have risen at a rate of 1.0°F/century (0.6°C/century), but the rate has increased to approximately three times the century-scale trend since 1976.
Land surface temperatures were second warmest for September. Temperatures were extremely warm throughout much of eastern Canada, where monthly anomalies in excess of 4.0° F(2.2°C) were widespread. Unusually warm temperatures also covered much of Asia and Europe. The global ocean surface temperature was warmest on record, and temperatures in much of the central and eastern equatorial Pacific were near average as the neutral phase of ENSO (El Niño/Southern Oscillation) continued.
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