Local Severe Weather Climatologies Local Severe Weather Climatologies for WSR-88D Radar Areas across for WSR-88D Radar Areas across

the United Statesthe United States

John A. HartJohn A. HartNOAA/NWS/NCEP Storm Prediction CenterNOAA/NWS/NCEP Storm Prediction Center

Norman, OklahomaNorman, Oklahoma

IntroductionIntroduction Developed a climatology of Developed a climatology of

severe weather reports severe weather reports (1980-2004)(1980-2004)

Useful due to equal areas of Useful due to equal areas of radar coverage regions.radar coverage regions.

Allows easy comparison Allows easy comparison between geographical between geographical regions.regions.

MethodologyMethodology Used the NWS/SPC severe weather Used the NWS/SPC severe weather

databasedatabase

Compiled reports within each WSR-Compiled reports within each WSR-88D radar coverage region for the 88D radar coverage region for the period of recordperiod of record

Created graphs, tables, figuresCreated graphs, tables, figures

Computed tornado threat Computed tornado threat probabilities based on tornado path probabilities based on tornado path width, length, and intensity ratingswidth, length, and intensity ratings

Objectively determined primary Objectively determined primary severe weather season for each severe weather season for each region.region.

NOTE: No additional quality-NOTE: No additional quality-control. Data is plotted and control. Data is plotted and tabulated directly from SPC tabulated directly from SPC database*.database*.

* Schaefer, J. T. and R. Edwards, 1999: The SPC Tornado/Severe Thunderstorm Database. Preprints, 11th Conf. On Applied Climatology, Dallas, AMS (Boston), 215-220.

http://www.spc.noaa.gov/climohttp://www.spc.noaa.gov/climo

Factors for distribution include:

-Meteorological factors-Population-Road networks-Spotter networks-Etc.

Geographical DistributionsGeographical Distributions25 years of data25 years of data

Little Rock, ArkansasDenver, ColoradoGreenville-Spartanburg, SCMilwaukee, Wisconsin

Severe Weather SeasonsSevere Weather SeasonsDefined by objective methodsDefined by objective methods

Max 10.5 on 06/09

Average of 2.9 for season

March 23rd July 27th

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, ColoradoDenver, Colorado-Season from Apr 28th – Sep 4th

- Max of 4.3 on June 5th

Atlanta, GeorgiaAtlanta, Georgia-Season Mar 14th – Aug 4th

- Max of 6.7 on May 2nd

Phoenix, ArizonaPhoenix, Arizona-Season Jun 28st – Sep 19th ?

- Max of 1.2 on Aug 14th

St. Louis, MissouriSt. Louis, Missouri-Season from Mar 29th – Aug 6th

- Max of 5.1 on May 28th

ComparisonsComparisonsDaily Occurrences & SeasonsDaily Occurrences & Seasons

ComparisonsComparisonsAnnual OccurrencesAnnual 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

ComparisonsComparisonsHourly OccurrencesHourly 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 ProbabilitiesTornado Strike Probabilities-Return Intervals for any point-Return Intervals for any point

Metro AreasMetro Areas*using nearest radar*using nearest radar

RETURN INTERVALRETURN INTERVAL*F2+ Tornadoes*F2+ Tornadoes

Oklahoma City, OKOklahoma City, OK 2,055 years2,055 yearsAtlanta, GAAtlanta, GA 2,267 years2,267 yearsSt. Louis, MOSt. Louis, MO 4,460 years4,460 yearsChicago, ILChicago, IL 5,222 years5,222 yearsWashington, D.C.Washington, D.C. 14,526 years14,526 yearsSan Antonio, TXSan Antonio, TX 25,306 years25,306 years* Point Probabilities

Rankings – Top 10Rankings – Top 10

Sig. Severe ReportsSig. Tornado ReportsSig. Tornado Threat(Annual Avg. Prob.)All Severe ReportsAnnual Severe DaysAnnual Tornado Days

ConclusionsConclusions Hopefully useful and informative Hopefully useful and informative

reference for severe weather distributions reference for severe weather distributions across the USA.across the USA.

Future plan to extend work to county-Future plan to extend work to county-based CWA areas.based CWA areas.

http://www.spc.noaa.gov/climohttp://www.spc.noaa.gov/climo