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Karsten A. Shein, Dennis P. Todey, F. Adnan Akyuz, James R. Angel, Timothy M. Kearns, and James L. Zdrojewski

New all-time extreme climate records have been set in several states over the past few years. These records highlighted a need to review the existing statewide climate extremes tables maintained by the NOAA National Climatic Data Center (NCDC). Also, since these tables were last up-dated, NCDC has greatly extended its digital data record into the past for many locations and has applied improved quality assurance processes to its archived data, revealing several potential new record values. To ensure the records maintained in the statewide climate extremes tables accurately reflect the most current and valid data available, the records were reevaluated. The all-time maximum and minimum temperature, all-time greatest 24-h precipitation and snowfall, and all-time greatest snow depth for each of the 50 states, Puerto Rico, and the U.S. Virgin Islands were manually examined to determine their validity, accuracy, accessibility, and provenance. NCDC's data holdings were scoured for values that might exceed established records, and the validity of each potentially record-breaking observation was evaluated. The revised extremes tables were vetted by the National Weather Service, regional climate centers, and state climatologists to ensure agreement. In conjunction with this revision, a new state climate extremes evaluation process has been established to formally consider any potential challenges to the existing records and update the records tables as necessary.

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Karsten A. Shein, Dennis P. Todey, F. Adnan Akyuz, James R. Angel, Timothy M. Kearns, and James L. Zdrojewski

Abstract

The NOAA National Climatic Data Center maintains tables for temperature and precipitation extremes in each of the U.S. states. Many of these tables were several years out of date, however, and therefore did not include a number of recent record-setting meteorological observations. Furthermore, there was no formal process for ensuring the currency of the tables or evaluating observations that might tie or break a statewide climate record. This paper describes the evaluation and revision of the statewide climate-extremes tables for all-time maximum and minimum temperature, greatest 24-h precipitation and snowfall, and greatest snow depth (the five basic climate elements observed on a daily basis by the NOAA Cooperative Weather Network). The process resulted in the revision of 40% of the values listed in those tables and underscored both the necessity of manual quality-assurance methods and the importance of continued climate-monitoring and data-rescue activities to ensure that potential record values are not overlooked.

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Russell S. Vose, Scott Applequist, Mark A. Bourassa, Sara C. Pryor, Rebecca J. Barthelmie, Brian Blanton, Peter D. Bromirski, Harold E. Brooks, Arthur T. DeGaetano, Randall M. Dole, David R. Easterling, Robert E. Jensen, Thomas R. Karl, Richard W. Katz, Katherine Klink, Michael C. Kruk, Kenneth E. Kunkel, Michael C. MacCracken, Thomas C. Peterson, Karsten Shein, Bridget R. Thomas, John E. Walsh, Xiaolan L. Wang, Michael F. Wehner, Donald J. Wuebbles, and Robert S. Young

This scientific assessment examines changes in three climate extremes—extratropical storms, winds, and waves—with an emphasis on U.S. coastal regions during the cold season. There is moderate evidence of an increase in both extratropical storm frequency and intensity during the cold season in the Northern Hemisphere since 1950, with suggestive evidence of geographic shifts resulting in slight upward trends in offshore/coastal regions. There is also suggestive evidence of an increase in extreme winds (at least annually) over parts of the ocean since the early to mid-1980s, but the evidence over the U.S. land surface is inconclusive. Finally, there is moderate evidence of an increase in extreme waves in winter along the Pacific coast since the 1950s, but along other U.S. shorelines any tendencies are of modest magnitude compared with historical variability. The data for extratropical cyclones are considered to be of relatively high quality for trend detection, whereas the data for extreme winds and waves are judged to be of intermediate quality. In terms of physical causes leading to multidecadal changes, the level of understanding for both extratropical storms and extreme winds is considered to be relatively low, while that for extreme waves is judged to be intermediate. Since the ability to measure these changes with some confidence is relatively recent, understanding is expected to improve in the future for a variety of reasons, including increased periods of record and the development of “climate reanalysis” projects.

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