U.S. HAS ITS WARMEST WINTER ON RECORD, 1999-2000, NOAA REPORTS
March 10, 2000 The winter of 1999-2000, December through February, was the warmest on record for the United States, according to statistics calculated by NOAA's scientists working from the world's largest statistical weather database. NOAA's National Climatic Data Center, in Asheville, N.C., holds data that goes back through the entire 105-year history of record keeping.
Working from this and current data, NOAA's seasonal winter temperature forecasts for the past two winters have called for much of the country having above normal temperatures. These were based on the expected impacts of La Niña and longer term warming trends.
The winter season preliminary
temperatures averaged 38.4 degrees F, 0.6 degrees F warmer than
the previous record, set just last year. In addition, the third
warmest winter on record occurred in 1997-1998, though tied with
1991-1992, at 37.5 degrees F. The last three winters therefore
have been the three warmest on record. The 1999-2000 winter continues
the pattern of warm winters established in 1980 with 67 percent
of the winter seasons since then being warmer than the long-term
Dryness also characterized the winter season, with 1999-2000 ranked as the 16th driest on record. Long-term dryness intensified in the northern Gulf states with Louisiana reporting its driest winter on record and Alabama and Mississippi their third driest. New Mexico and Arizona also experienced much below normal rainfall for the season. The only regions experiencing a wet season were the northern and central Rockies and a zone from the central Plains eastward to the Ohio Valley.
This winter Canadian air masses were not a major factor. Many locations from the northern Plains to New England established records for the latest date of their first seasonal snowfall, latest date without a temperature below freezing, longest snow-free period, or longest period between sub-zero temperatures. Although the eastern states experienced heavy snowfalls in the last two weeks of January, the accompanying cold air was short lived, as February established hundreds of daily maximum temperature records. Numerous locations from the northern Plains to New York set or tied their all-time maximum temperature records for the month.
These data sets are based on what is referred to as the boreal, or northern, winter in December, January and February, when the Northern Hemisphere experiences colder winter weather while the Southern hemisphere is experiencing summer weather patterns. The 1999-2000 season global land and ocean temperatures ranked as the 6th warmest on record, following the two warmest boreal winter seasons set in the past two years. Ocean temperatures ranked as 10th warmest at 0.5 F degrees above average. Land temperatures, however, remained well above average, with this season's anomaly (departure from long-term average) ranked as the 4th warmest on record, at 1.4 F degrees above average. The warmest global land temperature anomalies on record occurred in the past two boreal winters. Nearly the entire northern hemispheric land mass was warmer than the long-term average with only North Africa, the Mediterranean countries, Central America and parts of extreme eastern Asia below average. Most of North America, northern Europe, and Russia experienced well above normal warmth for the season.
Globally, precipitation was
above average through central and northern Europe, most of South
America, with the largest anomalies across southern Africa, Southeast
Asia, the Pacific Islands, and Australia. Above average rainfall
in February compounded by a dissipating tropical system, resulted
in catastrophic flooding in countries in southeastern Africa.
Major areas of dryness were the Mediterranean countries, Japan,
and most of North America.