National Climate Report - Winter (DJF) 2001
Contents of This Report:
||The graph to the left shows winter mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The 2000-2001 value is estimated from preliminary Climate Division data using the first difference approach. The current winter (December 2000-February 2001) ranked as the twenty-sixth coolest winter season since national records began in 1895. The preliminary nationally averaged temperature for the season was 31.75° F (-0.14°C), 1.21° F (0.67°C) below the long-term mean, and follows two of the warmest winters on record. Extremely cold conditions stretched from the Rocky Mountains to the East Coast in December as a series of strong cold fronts brought much below average temperatures to a large part of the nation. Milder winter conditions returned to much of the country in January and February. |
Winter season temperature values from 1895 through 2001 are available.
|The map to the right, based on approximately 250 airport stations, shows departures from the 1961-1990 normal temperatures for December 2000-February 2001. In general, the broad area from the Pacific Northwest through the center of the country into the south was cooler than normal. The Southwest region, portions of Florida and scattered areas around the Great Lakes were warmer than normal. Alaska experienced its warmest winter season on record. Hawaii was warm in the north and cool in the south, while Puerto Rico stations were warmer than normal.|| |
||Based upon preliminary data, winter 2000-2001 ranked below the long-term mean for precipitation for the second continuous winter season. The wettest winter season on record was 1997-1998, just three years ago.|
|The preliminary National Precipitation Index ranked winter 2000-2001 as the forty-first driest such season since national records began in 1895, tying with 1942 and 1972. There is a rather large difference between the Precipitation Index rank and the National Rank map. The standardized index takes local climatology into account. This winter season was marked by atypical precipitation in some areas. The Southeast and the Pacific Northwest which normally receive abundant precipitation during winter months were much drier than normal, but the Central Plains, which usually receives little precipitation during the winter season, experienced above normal precipitation.|| |
Snow cover duration for the Winter (December 2000 - February 2001), as observed by satellite, exceeded the 1992-2001 average over a large part of the nation (see map to left). The greatest anomalies were in the central Great Plains and parts of the Pacific Northwest. The snow cover this season is primarily the result of a series of winter storms during November and December 2000, which brought snow that has been slow to melt in the northern Plains and Northeast. Seasonal snowfall through the end of February totaled nearly 200 inches (508 cm) in parts of the Northeast.
Current data are based on preliminary reports from River Forecast Center stations and First and Second Order airport stations obtained from the National Weather Service (NWS) Climate Prediction Center and real time Global Telecommunications System (GTS) monthly CLIMAT summaries. THE CURRENT DATA SHOULD BE USED WITH CAUTION. These preliminary data are useful for estimating how current anomalies compare to the historical record, however the actual values and rankings for the current year may change as the final data arrive at NCDC and are processed.
The following NCDC datasets are used for the historical U.S. data: the climate division drought database (TD-9640), and the hurricane datasets (TD-9636 and TD-9697). It should be noted that the climate division drought database consists of monthly data for 344 climate divisions in the contiguous United States. These divisional values are calculated from the 6000+ station Cooperative Observer network.