National Overview - December 2000


NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

U.S. December Temp 1895-2000

Contents of This Report:

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The North American 500 mb Maps for December

The upper-air pattern during December reflected negative height anomalies from the central Plains eastward to the Atlantic coast and positive anomalies from the central Rockies westward. Much below normal temperatures dominated the country from the northern Rockies to Texas, eastward to the Atlantic, while warmer than normal temperatures were prevalent in the Southwest.


The trough axis was situated far enough to the east to prevent any influx of Gulf moisture so most of the eastern half of the country averaged near to below normal for precipitation. However, wetter than normal conditions did exist in the extreme Northeast, the western Great Lakes and portions of the central and southern Plains. Along with the positive height anomalies, much drier than normal conditions dominated from the Rockies westward.
NA 500mb Map
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Additional information on hydrometeorological analysis and forecasting can be found at the Hydrometeorological Prediction Center's Web Page. The principles behind the 500 mb flow are briefly explained here.
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Top of Page National Temperature - December

U.S. December Temperature
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The December 2000 monthly mean temperature averaged across the contiguous United States, based on data from the U.S. Historical Climate Network (USHCN) and preliminary data from the Climate Division Database, ranked as the seventh coolest December since records began in 1895. The preliminary nationally averaged temperature for December 2000 was 28.9° F, 4.4° F below the long-term mean. The actual December temperature values from 1895 through 2000 are available. December 2000 was the first such month in eight years to be below the long-term mean. A loop of weekly temperature anomalies from October 1 is available.
The map to the right, based on approximately 250 airport stations, shows departures from the 1961-1990 normal temperatures for December 2000. In general, the country was cooler than normal from the western high Plains to the Atlantic coast. Much cooler than normal conditions existed from the northern and central Plains eastward to the mid-Atlantic Coast and south to the Gulf Coast. The persistent cooler than normal conditions are reflected in below-normal day-to-day temperature variability across the Southeast while lack of significant frontal passages provided less day-to-day variability from the Rockies westward. All of the Alaskan reporting stations were warmer than normal allowing for the sixth warmest December statewide since 1917. The Hawaiian stations averaged about normal.
U.S. December Temperature Departures
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Animated TZ Map200001/200012
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The standardized temperature anomalies for December 2000 show abnormally cold conditions from the central Plains eastward to the mid-Atlantic Coast and south to the Gulf of Mexico. Cooler than normal conditions are depicted over much of the remaining third of the country except for the Southwest. Abnormally warm conditions dominated this area. This compares well with other temperature indicators. The map animation provided shows the geographical pattern of temperature anomalies for the last 12 months compared to a base period of 1931-1990.

Extreme minimum temperatures, interpolated from observations recorded at approximately 800 National Weather Service Stations for December 2000, reached values lower than -30° F over extreme northern Minnesota and portions of southwestern Wisconsin. Extreme minimum temperatures below 10° F were observed north of a line from central Washington, south through the Great Basin, northern Arizona and New Mexico, eastward through extreme western North Carolina and northeastward to the New Jersey coast. Reported low temperatures stayed above 30° F for the southern third of Florida, the delta region of Louisiana, extreme south Texas, portions of southern Arizona, and a good portion of the immediate Pacific coast from California to Oregon. The northern two-thirds of Alaska saw extreme minimum temperatures lower than -30° F while the extreme southeastern coast of Alaska remained above 0° F.
U.S. December Temperature Departures
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Animated TZ Map200001/200012
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Data collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville indicate that temperatures in the lower half of the atmosphere (lowest 8 km) were the third coldest on record over the U.S. during December. The average lower tropospheric temperature over the continental U.S. during December 2000 was 1.26° F below the 1979-1998 long-term mean.
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Top of Page National Precipitation - December

U.S. December Precipitation, 1895-2000
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Based upon preliminary precipitation data, December 2000 ranked as the 14th driest such month since records began in 1895. Only two of the last eight and six of the last 16 Decembers have averaged above the long-term mean. Despite drier than normal conditions nationwide, snowcover extent was widespread at times during the month. This can also be seen in the National Weather Service/Climate Prediction Center snowcover frequency map for December. On this map the frequency legend refers to the number of weeks during the month that the ground was snow covered.
The preliminary national standardized precipitation index ranked December 2000 as the 26th driest December since records began.
U.S. December Precipitation Index, 1895-2000
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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.

Citing This Report

NOAA National Climatic Data Center, State of the Climate: National Overview for December 2000, published online January 2001, retrieved on October 22, 2014 from http://www.ncdc.noaa.gov/sotc/national/2000/12.