National Overview - July 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. July Temp 1900-2000

Contents of This Report:

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The North American 500 mb Maps for July

The upper-air pattern during July consisted of a dominant high pressure ridge over the western two-thirds of the U.S. and a trough over the eastern third of the country.

The mean upper-level ridge over the West provided warmer than normal conditions for the Rocky Mountain region as well as the Deep South from Texas to Florida. At the same time, prevalent troughiness from the mid-Mississippi Valley through the Northeast allowed for much cooler than normal temperatures, especially for the Ohio Valley, central Appalachians, and the mid-Atlantic region.

Due to the eastern trough, wetter than normal conditions were noted from the northern Great Plains region through the central Great Lakes states, into southern New England. The western ridge provided dry conditions from the Pacific Northwest, through the inter-mountain West and Southwest, as well as portions of the South. 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 - July

U.S. July Temperature
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The July 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 38th warmest July since 1895. The preliminary nationally averaged temperature for July 2000 was 74.80°F, 0.47°F above the long-term mean. Nearly 11% of the country was much warmer than normal during July while about 12% of the country was much cooler than normal. The actual July temperature values from 1895 through 2000 are available.

The map to the right, based on approximately 250 airport stations, shows departures from the 1961-1990 normal temperatures for July 2000. In general, the Pacific Coast and areas from the Central Plains eastward to the mid-Atlantic and Northeast were cooler than normal. The south Atlantic, Gulf Coast, and points westward to Arizona, as well as the western High Plains were warmer than normal. Most of the interior and northern Alaska stations were cooler than normal while most of the southern coastal sites were near normal. The Hawaiian stations averaged only slightly above normal. U.S. July Temperature Departures
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U.S. July Temperature Maxes
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Extreme maximum temperatures during July 2000 exceeded 110° F through parts of southern California and southwestern Arizona. Temperatures exceeded 100° over most of the remainder of the Southwest as well as the inter-mountain West and from the northern High Plains south to Texas and eastward through southern South Carolina. Maximum temperatures failed to exceed 90° F in the highest elevations of the inter-mountain West, the immediate Pacific Coast, and from the western Great Lakes south through the central Appalachians, the interior mid-Atlantic region, and Northeast. Approximately 700 ASOS stations were used in this analysis.

The number of days with high temperatures in excess of 90° F exceeded the normal number of days of greater than 90°F for July over most of the Rocky Mountain region and from central Arizona eastward through the Southeast. Within this area, the departure exceeded the normal by at least six days over most of Wyoming, south-central Montana, the Gulf Coastal areas from central Texas to the Mississippi Delta, and from the panhandle of Florida, northward through most of Alabama, northern Georgia, southeastern Tennessee and the upstate of South Carolina. U.S. July Temperature Departures 90+
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U.S. July Consec 90+ Days
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For more than 25 consecutive days during July, maximum temperatures exceeded 90°F in the deserts of southern California, southwestern Nevada, and from southern Arizona, eastward through most of the southern half of Texas. Similar values were observed in much of central Mississippi and Alabama. Maximum temperatures failed to exceed 90° F in the highest elevations of the inter-mountain West, the immediate Pacific Coast, and from the western Great Lakes south through the central Appalachians, the interior mid-Atlantic region, and Northeast.

The standardized temperature anomalies for July 2000 show abnormal warmth in the central Rockies as well as warmer than normal conditions from New Mexico to Georgia. Cooler than normal conditions are depicted in the Great Lakes states, mid-Mississippi Valley region, and from North Carolina through Maine. Much of interior California was also much cooler than normal. 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. Animated TZ Map199908/200007+
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Top of Page National Precipitation - July

U.S. July Precipitation, 1895-2000
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Based upon preliminary precipitation data, July 2000 ranked as the 14th driest such month since 1895. About 23% of the country was much drier than normal during July while about four percent of the country was much wetter than normal.
The preliminary national standardized precipitation index ranked July 2000 as the eighth driest July since 1895. U.S. July Precipitation Index, 1895-2000
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The map to the right, based on approximately 250 airport stations, shows July 2000 total precipitation as a departure from 1961-1990 station normals. Above-normal precipitation can be found in the Aleutians, extreme north, central, and southeastern Alaska, while most of the other Alaskan stations were near normal. The Hawaiian stations were near to slightly wetter than normal. On the mainland U.S., stations were predominantly wetter than normal from the Northeast and mid-Atlantic to the northern and central Great Plains. Stations were drier than normal across most of the Southeast, west through the deep South and from the Rockies to the Pacific. U.S. July Precipitation Departures
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Long-term drought areal coverage (as measured by the Palmer Drought Index) increased when compared to June, with about 31% of the country in severe to extreme drought at the end of July compared to about 18% at the end of June. The percent area of the country experiencing severe to extreme wetness has been hovering around 3 to 5 percent since late 1999. During July, above normal precipitation fell from the northern Plains, southeastward through the mid-Mississippi Valley. Above normal precipitation amounts were also noted in northern California and southern Oregon as well as the central Great Lakes region and most of the mid-Atlantic and Northeast. Limited rainfall did little to improve drought conditions in parts of the Southwest, intermountain West, and Southeast where July precipitation amounts were generally below normal. Severe to extreme drought persisted across the Gulf Coast into the southern Appalachians, parts of the central Plains, and in the Rocky Mountains. Although severe to extreme drought persists in many parts of the U.S., several droughts in the past one hundred years have covered a much larger area for a much longer time (see graph below right). The current drought, in terms of U.S. areal coverage, is the worst since the drought of the late 1980's.

USPA, 07/2000
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USPA 1900-01/2000-07
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Top of Page National Temperature

The January-July 2000 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 warmest such seven-month period since 1895. The preliminary nationally averaged temperature for January-July 2000 was 54.85°F, 2.81°F above the long-term mean. The actual year-to-date data values from 1895 through 2000 are available. US Jan-July Temp
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Top of Page National Precipitation - January-July 2000

U.S. Jan-July Precipitation, 1895-2000
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Based upon preliminary precipitation data, January-July 2000 ranked as the 32nd driest such seven-month period since 1895. About 11% of the country was much drier than normal while about five percent of the country was much wetter than normal. January-July 2000 is the first such period in ten years to average below the long-term mean.


The preliminary national standardized precipitation index ranked January-July 2000 near the long-term mean.
U.S. Jan-July 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 July 2000, published online August 2000, retrieved on July 30, 2014 from http://www.ncdc.noaa.gov/sotc/national/2000/7.