13 Severe Thunderstorm Database NSWW2005

Slide1 : The SPC Severe Thunderstorm Database


SPC Database Derivation : SPC Database Derivation NWS/ OCWWS/ Verification SPC NCDC FTORNADO ONETOR WFO StormDat Info Apr./May next year due to 60 day lag & Quality Control


Slide3 : SPC Severe Thunderstorm DATABASE A Severe Thunderstorm is a thunderstorm that produces a tornado, winds of at least 50 knots (58mph), and or hail at least 0.75 inch in diameter. Structural wind damage may imply the occurrence of a severe thunderstorm. Tornadoes since January 1, 1950 Wind and Hail since January 1, 1955


Slide4 : SPC Data Source Since 1972… data agrees with NOAA Storm Data. Prior to 1972… tornado data -- from Storm Data (or its predecessor Climatological Data National Summary - Storm Data and Unusual Phenomena) wind and hail data --from real time information collected by the U.S. Air force. Errors corrected when identified (if possible) 1972 Wind & Hail data incomplete


Uniqueness of SPC Tornado Database : Uniqueness of SPC Tornado Database SPC Tornado Database is EVENT based NCDC (Ashville) Database is SEAGMENT based For 1950 - 2001: SPC had 43,467 tornadoes NCDC had 46,472 tornado segments


What is a tornado Segment? : What is a tornado Segment? Pre-1996 Enter/left a county with fatality/injury Crossed a State boundary Since 1996 Tornado segments are divided by counties and States When tornado makes “sharp turns” within a county in order to adequately describe the path Sep 20, 2002 Indiana Tornadoes Tornado #1 = 3 segments Tornado #2 = 9 segments


Example of Tornado Segments : Example of Tornado Segments 1 2 3 4


Tornadoes v. Tornado Segments 1950-2001 : Tornadoes v. Tornado Segments 1950-2001


SPC Database Fields : SPC Database Fields Year Number (by State) State Month Day Date Time (CST) Tornado Number No-States State-Tornado number Segno (1=entire tornado, 2 = state portion) STLAT/STLON SPLAT/SPLON Length Area F*Area Width (Max) Fatal Injuries Damage CO (1-4) F PL PW


SPC Severe Thunderstorm Wind & Hail Report Database : SPC Severe Thunderstorm Wind & Hail Report Database 68,612 Hail reports back through 1955 Reports within one county must be separated by 10 miles or 15 minutes if less than 65 kts and did not cause deaths or injuries or did less than $500K damage 203,698 Wind back through 1955 Reports within one county must be separated by 10 miles or 15 minutes if smaller than 2” and did not cause deaths or injuries or did less than $500K damage Format similar to Tornado Database, except F is relplaced by diameter (hundredths of inches) or wind speed (knots). Other tornado related fields are left blank.


Severe Thunderstorm Reports : Severe Thunderstorm Reports


F-Scale Evaluation : F-Scale Evaluation “The tornado first touched down on the eastern edge of General Smallwood State Park just north of Rison. It pushed east-southeast and passed just south of Pisgah where it grew to F2 strength. The tornado moved through Mount Pisgah and damaged homes on Ripley Road between Ripley and Garden Estates. The twister continued to move east through rural lands south of Hawthorne Road (Route 255) passing just north of the community of Graystone. Next, it moved through the communities of Habre de Venture, Longmeade, Clamber Hill, Hawthorne Manor, and Hillendale about 3 miles west of downtown La Plata. The tornado, now F3 strength, hit the western portion of La Plata next, moving directly through the neighborhoods of Valley View, Morgan's Ridge, Quailwood, and Haldane. The tornado, now F4 strength, continued east into the downtown area where it crossed through the intersection of Route 301 and 6. Damage was found on either side of Route 6 with the most severe devastation occurring on the south side of the highway.” F-Scale is misinterpreted in describing tornado strength. This tornado is causing more damage rather than gaining strength! Little description of the tornado itself! How is it known the winds became stronger?


United States Tornadoes : United States Tornadoes


F-Scale Percentages1950 - 2001 : F-Scale Percentages 1950 - 2001 Number Deaths


Which is the F5 Tornado? : Which is the F5 Tornado? F2 Burkburnett County, TX March 7, 2002 F5 Oklahoma City, OK May 3, 1999 Symposium on F-Scale and Severe-Weather Assessment


Slide21 : Manhatten, KS May 31, 1948 F-2 Length – 20 km Width – 130 m Seymour, TX April 10, 1979 F-2 Length – 17 km Width – 300 m


Grand Gulf, MSApril 17, 1978F-3 : Grand Gulf, MS April 17, 1978 F-3


Slide33 : Fall Velocity ~ 120 mph


3/4" and Larger Hail Reports : 3/4" and Larger Hail Reports


Slide38 : © Bill Bunting © Bill Bunting © Bill Bunting © Bill Bunting


Severe Thunderstorm Wind Reports : Severe Thunderstorm Wind Reports


Slide40 : Severe Thunderstorm Wind Reports 1955-2001 Thunderstorm Wind Gusts > 58 mph (>75 mph) Thunderstorm Wind Gusts > 75 mph Percent of Wind Reports from Damage Only


Slide41 : January Thunderstorm Wind Reports January Thunderstorm Gusts > 58 mph January Thunderstorm Gusts > 75 mph April Thunderstorm Wind Reports April Thunderstorm Gusts > 58 mph April Thunderstorm Gusts > 75 ph


Slide42 : July Thunderstorm Wind Reports July Thunderstorm Gusts > 58 mph July Thunderstorm Gusts > 75 mph October Thunderstorm Wind Reports October Thunderstorm Gusts > 58 mph October Thunderstorm Gusts > 75 mph


Slide43 : © K. Dewey, High Plains Regional Climate Center Hallam, NE – May 22, 2004, 2 ½ miles wide