Local Severe Weather Climatologies for WSR-88D Radar Areas across the United States John A. Hart NOAA/NWS/NCEP Storm Prediction Center Norman, Oklahoma

Introduction  Developed a climatology of severe weather reports ( )  Useful due to equal areas of radar coverage regions.  Allows easy comparison between geographical regions.

Methodology  Used the NWS/SPC severe weather database  Compiled reports within each WSR-88D radar coverage region for the period of record  Created graphs, tables, figures  Computed tornado threat probabilities based on tornado path width, length, and intensity ratings  Objectively determined primary severe weather season for each region.  NOTE: No additional quality- control. Data is plotted and tabulated directly from SPC database*. * Schaefer, J. T. and R. Edwards, 1999: The SPC Tornado/Severe Thunderstorm Database. Preprints, 11th Conf. On Applied Climatology, Dallas, AMS (Boston),

Factors for distribution include: -Meteorological factors -Population -Road networks -Spotter networks -Etc. Geographical Distributions 25 years of data Little Rock, ArkansasDenver, ColoradoGreenville-Spartanburg, SCMilwaukee, Wisconsin

Severe Weather Seasons Defined by objective methods Max 10.5 on 06/09 Average of 2.9 for season March 23 rd July 27 th 1.Determine average daily number of severe weather reports - 7-day running average of all reports (hail, wind, torn) 2.Any day with value above average meets threshold for season. 3.Short duration minima are ignored. (5-days or less)

Denver, Colorado -Season from Apr 28 th – Sep 4 th - Max of 4.3 on June 5 th Atlanta, Georgia -Season Mar 14 th – Aug 4 th - Max of 6.7 on May 2 nd Phoenix, Arizona -Season Jun 28 st – Sep 19 th ? - Max of 1.2 on Aug 14 th St. Louis, Missouri -Season from Mar 29 th – Aug 6 th - Max of 5.1 on May 28 th Comparisons Daily Occurrences & Seasons

Comparisons Annual Occurrences Kansas City, Missouri - Recent increase in hail Pittsburgh, Pennsylvania - Mostly wind reports Hastings, Nebraska - Mostly hail reports Shreveport, Louisiana - Decreasing trend last 10 years

Comparisons Hourly Occurrences Houston, Texas - Severe threat all night Albany, New York -Rarely severe between 05-14z - Max threat 21z Glasgow, Montana - Wind threat lags hail threat - Max threat 02z. Tallahassee, Florida -Hail and Wind are diurnal - Tornadoes are not

Tornado Strike Probabilities -Return Intervals for any point Metro Areas *using nearest radar RETURN INTERVAL *F2+ Tornadoes Oklahoma City, OK 2,055 years Atlanta, GA 2,267 years St. Louis, MO 4,460 years Chicago, IL 5,222 years Washington, D.C. 14,526 years San Antonio, TX 25,306 years * Point Probabilities

Rankings – Top 10 Sig. Severe Reports Sig. Tornado ReportsSig. Tornado Threat (Annual Avg. Prob.) All Severe Reports Annual Severe Days Annual Tornado Days

Conclusions  Hopefully useful and informative reference for severe weather distributions across the USA.  Future plan to extend work to county- based CWA areas. 