Isolated tornado in a weakly sheared, moderately unstable environment

All,

A thunderstorm in vicinity of the Wayne/Wilson County border acquired rotation, briefly exhibited supercellular characteristics and produced a tornado in a weakly sheared environment around 1125 am this morning. Effective bulk shear values this morning were ~20 knots.. barely enough for multicell organization. However, surface analysis showed a meso-low in vicinity of the Wayne/Sampson/Johnston county border with a weak front extending NE/ENE into Wilson/Edgecombe/Martin counties. Despite very weak low level flow (virtually no speed shear), backed surface winds in vicinity of the boundary contributed to 50-100 m2/s2 of 0-1km SRH. The environment was very moist/tropical with LCL’s  in the 500-750 meter range, PWAT values ~2.25″ and MLCAPE values between 500-1500 J/kg.

Given that tornadoes are rare in August across central NC (especially in the absence of a tropical cyclone or the remnants thereof), I thought this was a good example of a circumstance where strong situational awareness of subtle surface features (via manual surface analysis and/or spc mesoanalysis) can pay large ‘dividends’ when it comes to catching these difficult events!

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
442 PM EDT SAT AUG 6 2011

...TORNADO CONFIRMED IN FAR SOUTHERN WILSON COUNTY NORTH CAROLINA...

LOCATION...FAR SOUTHERN WILSON COUNTY NEAR BLACK CREEK
DATE...AUGUST 6 2011
ESTIMATED TIME...1125 AM EDT TO 1130 AM EDT
MAXIMUM EF-SCALE RATING...EF0
ESTIMATED MAXIMUM WIND SPEED...85 MPH
MAXIMUM PATH WIDTH...50-100 YARDS
PATH LENGTH...3 MILES
BEGINNING LAT/LON...35.595790N / -77.927176W
ENDING LAT/LON...35.589997N / -77.874853W
* FATALITIES...0
* INJURIES...0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

...SUMMARY...
THE NATIONAL WEATHER SERVICE IN RALEIGH NC HAS CONFIRMED A TORNADO
IN FAR SOUTHERN WILSON COUNTY NEAR BLACK CREEK ON AUGUST 6 2011.
THE FIRST REPORTS OF DAMAGE WERE OBSERVED JUST WEST OF FRANK PRICE
CHURCH ROAD WHERE A MOBILE HOME AND BARN WERE DAMAGED AND SEVERAL
TREES WERE DOWNED. THE TOUCHDOWN TIME WAS ESTIMATED AT 1125 AM EDT.
ADDITIONAL TREES WERE DOWNED ALONG AND ESPECIALLY SOUTH OF JAYCROSS
ROAD BETWEEN FRANK PRICE ROAD AND PELT ROAD. FOUR TURKEY HOUSES ON
PELT ROAD WERE DAMAGED WITH ONE BARN VIRTUALLY DESTROYED. DEBRIS WAS
BLOWN 300-400 YARDS TO THE EAST. THE TORNADO APPEARED TO WEAKEN IN A
WOODED AREA EAST OF PELT ROAD AT APPROXIMATELY 1130 AM EDT. A TOTAL
OF 7 MOBILE HOMES HAD DAMAGE WITH MOST OF THE DAMAGE MINOR IN
NATURE.

THE NWS WOULD LIKE TO THANK THE STAFF OF THE WILSON COUNTY EMERGENCY
MANAGEMENT FOR THEIR ASSISTANCE.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/RAH.

FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO
THE FOLLOWING CATEGORIES:

EF0...WIND SPEEDS 65 TO 85 MPH.
EF1...WIND SPEEDS 86 TO 110 MPH.
EF2...WIND SPEEDS 111 TO 135 MPH.
EF3...WIND SPEEDS 136 TO 165 MPH.
EF4...WIND SPEEDS 166 TO 200 MPH.
EF5...WIND SPEEDS GREATER THAN 200 MPH.
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About bvincentnws

Meteorologist National Weather Service 2003 - Current
This entry was posted in Convection. Bookmark the permalink.

One Response to Isolated tornado in a weakly sheared, moderately unstable environment

  1. When I saw the tornado warning, I ran in and checked the radar and SPC mesoanalyses. It looked quasi-supercellular for a handful of volume scans, and interestingly it was nestled within a roughly 2 county area of supercell composite > 1 in the SPC mesoanalyses. I guess the pre-existing MCV provided just enough local enhancement to the mesoscale environment there?! Certainly an interesting case given the general lack of broad scale vertical wind shear.

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