Comparison of November 15, 2008 Killer Tornado Outbreak with the December 2, 2009 Non Tornado Event

Transcription

1 Comparison of November 15, 2008 Killer Tornado Outbreak with the December 2, 2009 Non Tornado Event The two events featured similar patterns but with much different results in central NC. The slides on the following pages are designed to serve as a reference for discussion. In many aspects, the events were very similar with the synoptic upper air and surface pattern. One obvious difference between the two events is a much greater amount of surface based CAPE in the 11/15 case then the 12/02 event which would obviously support more surface based convection and allow a storm to utilize the surface instability and drive a circulation to the surface. A review of the radar imagery shows that at the time of the tornadoes in central NC, the convection during the 11/15 event was not embedded in a large convective rain shield as was the case with the 12/02 event. In addition, the 11/15 tornadic supercells were long lived, originating in SC in a region of similar instability to that over eastern NC where they eventually produced tornadoes. I believe the 1988 Raleigh Tornado was spawned by a long lived supercell originating in SC. More recently, on March 28, 2010, a long lived supercell produced 4 tornadoes in the western Piedmont of North Carolina with the first tornado touching down just north of the South Carolina state line. Jonathan Blaes NOAA/NWS Raleigh, NC

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3 On 2009/12/09 there were several reports of wind damage in the southern and central Coastal Plain of NC. Other severe weather was observed during the afternoon across GA/SC. Most of the severe weather on was reported as tornadoes and related to one or two long lived supercells.

4 No tornadoes were confirmed during the evening or early morning hours of 12/03/09 Most of the tornadoes on 11/15/08 occurred between 07 and 09 UTC

5 2009/12/03

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7 2009/12/02

8 MESOSCALE DISCUSSION 2191 NWS STORM PREDICTION CENTER NORMAN OK 0731 PM CST WED DEC AREAS AFFECTED...ERN SC...ERN NC CONCERNING...TORNADO WATCH VALID Z Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 789 CONTINUES. THE TORNADO THREAT ACROSS WW 791 WILL CONTINUE TO INCREASE ACROSS NC OVER THE NEXT 1-2 HOURS. A NEW TORNADO WATCH WILL LIKELY BE NEEDED WITHIN THE HOUR ACROSS CNTRL NC INTO SERN VA. THE AIRMASS ACROSS WW 791 IS RAPIDLY DESTABILIZING DUE TO STRONG MOISTURE ADVECTION AS A WARM FRONT MOVES QUICKLY NWD ACROSS NC. SFC DEWPOINTS ARE ALREADY IN THE UPPER 60S F IN GREENVILLE NC AND THIS MOISTURE SHOULD REACH THE NC-VA STATE-LINE DURING THE 02Z TO 03 TIMEFRAME. THE MOISTURE COMBINED WITH A STRONG SHEAR ENVIRONMENT ALREADY IN PLACE IS INCREASING THE POTENTIAL FOR ROTATING STORMS AND TORNADOES. TORNADOES WILL BE POSSIBLE WITH DISCRETE CELLS AHEAD OF A BAND OF RAIN CURRENTLY WEST OF THE RALEIGH/DURHAM VICINITY. ROTATING CELLS WILL ALSO BE POSSIBLE EMBEDDED IN THE RAIN BAND ESPECIALLY SWD TOWARD THE SC STATE-LINE WHERE SFC DEWPOINTS ARE APPROACHING 70 F. AS LARGE-SCALE ASCENT SPREADS ACROSS NC...THE LOW-LCL HEIGHTS AND 0-1 KM SHEAR OF KT SHOULD SUPPORT SUPERCELL DEVELOPMENT WITH A STRONG TORNADO POSSIBLE AS THE LOW-LEVEL JET SHIFTS NNEWD INTO THE CNTRL PART OF WW BROYLES.. 12/03/2009

9 MESOSCALE DISCUSSION 2386 NWS STORM PREDICTION CENTER NORMAN OK 0210 AM CST SAT NOV CONCERNING...TORNADO WATCH VALID Z Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH CONTINUES. TORNADO WATCHES 932/933 CONTINUE ACROSS EASTERN SC AND CENTRAL/EASTERN NC UNTIL 11Z/13Z RESPECTIVELY...WITH A RECENTLY ISSUED WFO EXTENSION ACROSS FAR SOUTHEAST VA. A DISTINCT RISK FOR ISOLATED TORNADOES AND WIND DAMAGE WILL CONTINUE OVERNIGHT. LATEST SUBJECTIVE SURFACE ANALYSIS FEATURES A GENERAL SW-NE ORIENTED WARM FRONT FROM NORTHERN GA INTO UPSTATE SC/EAST CENTRAL NC AND SOUTHEAST VA...WITH UPPER 60S/LOWER 70S F SURFACE DEWPOINTS PREVALENT EAST OF THIS BOUNDARY. A NORTHEAST-ADVANCING EMBEDDED SPEED MAXIMA AND A FAVORABLE KINEMATIC/HIGHLY SHEARED ENVIRONMENT WILL CONTINUE TO CONTRIBUTE TO WELL-ORGANIZED TSTMS INCLUDING SUPERCELLS/BOWS ALONG AND EAST OF THIS WARM FRONT ACROSS EASTERN SC AND ESPECIALLY EASTERN NC...AND INTO SOUTHEAST VA WITHIN THE NEXT FEW HOURS. TORNADO DAMAGE WAS RECENTLY REPORTED SOUTHEAST OF THE RALEIGH AREA IN JOHNSTON COUNTY. REGIONAL WSR-88D DERIVED WIND PROFILES REFLECT A STRONG LOW LEVEL JET WITH KT SOUTH-SOUTHWESTERLY FLOW AROUND 1 KM...WHICH IS CONTRIBUTING TO MS/S2 0-1 KM SRH...GUYER.. 11/15/2008

10 300 hpa

11 500 hpa

12 850 hpa

13 Surface Theta-E

14 SBCAPE

15 MLCAPE

16 0-1km SRH

17 0-6km shear

18 SPC Sig Tor effective layer

19 RUC profiles