Event Summary
     National Weather Service, Raleigh NC

November 16, 2006 Severe Weather Event
Updated 2006/12/11

Satellite image of Deep Low Pressure System - Click to enlarge
(Click on the image to enlarge.)


Event Headlines -
...Thunderstorms with damaging winds developed ahead of a cold front and approached central North Carolina shortly after midnight on November 16, 2006...
...Thunderstorms with very strong rotation and tornadic potential developed across the Sandhills and Coastal Plain of central North Carolina after sunrise...
...No tornado touchdowns were reported across central NC and damage throughout the event was primarily limited to sporadic reports of downed trees...


Event Overview -
A round of late season severe weather affected North Carolina on the morning of November 16, 2006 as a potent upper level low lifted north-northeast along and just west of the Appalachian mountains. A 992mb surface low accompanied the upper level low on the windward side of the mountains. The orientation of the surface pressure gradient and the low level jet aloft over central/eastern North Carolina created very strong low-level wind shear on Thursday morning. Surface winds of 15-20 kts from the southeast beneath a 50-65 kt south southwest flow at 850 mb created a favorable environment for rotating storms, with surface helicity values in the extreme 400-600 m2/s2 range. Although instability was limited to only 250-750 J/kg throughout the event, the presence of strong upper-level divergence ahead of a 130 kt 300 mb jet swinging around the eastern portion of the upper low over North Carolina helped several convective cells develop and survive the strong shear despite weak thermodynamics. Although several convective cells developed strong rotation throughout the morning and there were a few funnel cloud sightings, no tornadoes touched down across the NWS Raleigh county warning area. Damage was limited to sporadic reports of downed trees across the area.


Severe Weather Reports -
Text of severe weather reports across central North Carolina





Radar Analysis and Warning Methodology on November 16, 2006

Between midnight and 500 AM Thursday morning, several severe thunderstorm warnings were issued across central NC. These warnings were generally prompted by bowing line segments in reflectivity imagery combined with VAD wind profile (VWP), WSR-88D velocity and local 00Z RAOB data showing 50-55kt winds 5000-10000 ft above ground level (AGL). Since the 0.5 degree elevation scan from KRAX and neighboring radars overshoots the lowest 5000-10000 ft in the west/northwest piedmont and low-level storm structure and velocity data cannot be sampled, storm severity was assessed primarily by recognizing structural characteristics aloft such as rear-inflow notches, bowing line segments and mid-altitude radial convergence (MARC). Volume products such as composite reflectivity, echo tops and vertically integrated liquid (VIL) were of limited use in this event because of the weak thermodynamic environment (very marginal instability), however, these products were helpful at times with regards to highlighting strengthening convective cells.

At 0710Z, a storm in central Randolph County developed a pronounced rear-inflow notch in the base reflectivity and began to bow out. A severe thunderstorm warning was issued for northeast Randolph County and Alamance County in response to this feature. At 0714Z, base reflectivity and storm-relative velocity revealed that the northern portion of the bow (directly over the town of Liberty in NE Randolph County) had developed into a structure like that of a book-end vortex. Damage was reported with this cell in the town of Liberty in extreme northeast Randolph County.

At 0916Z (416AM), a cell moving northeast into Johnston County intensified with a 30-40 kg/m2 VIL that persisted through the next several volume scans. At 0929Z, 50 knot inbound winds on the base velocity at 600 ft AGL prompted a severe thunderstorm warning for NW Johnston and SE Wake counties, valid from 0930Z-1000Z. A spotter reported a 62 mph wind gust with this cell in the town of Clayton in NW Johnston County at 0950Z. In this case, because the cell traveled directly toward and over the radar, low-level storm structure and velocities were well-sampled, leading to higher confidence that severe weather would occur.

At 1100Z, a supercell thunderstorm moved onshore into Brunswick County in extreme southeastern NC. This cell continued to intensify as it moved inland into an environment with higher helicity. The storm subsequently moved north through Columbus County where it spawned an F3 tornado, killing 8 people and injuring 20 others. This supercell continued north into Pender and Duplin counties by 1200Z. Tornado warnings were issued by NWS Wilmington and NWS Newport for Columbus, Pender and Duplin counties. With a history of producing a killer tornado and an impressive, sustained low-level rotation observed from KRAX, KLTX and KMHX as the storm continued moving north, a tornado warning was issued by NWS Raleigh for Wayne County at 1234Z (734AM). This warning was issued while the storm was near Kenansville in central Duplin County, allowing 16 minutes lead time before the strong circulation even reached the Duplin/Wayne County border. The storm continued to show strong rotation as it moved NNE through eastern Wayne County, exiting into extreme western Greene County and southern Wilson County by 1315Z (815AM). A tornado warning was also issued for Wilson County as the storm continued north but the the circulation soon fell apart and the storm weakened shortly thereafter. Amazingly, no damage was reported with this storm as it crossed Wayne County.

By 1330Z, the remnants of the supercell that produced the Columbus County tornado were in Wilson County and another distinct line of heavy showers had developed ahead of the cold front across central North Carolina. At 1330Z, the line of heavy showers extended from Columbus County north through Cumberland County into Wake County. Individual cells within the line were moving to the N/NNE at 50-60 mph while the whole line slowly moved east towards the coastal plain. As the line approached the Interstate 95 corridor it intensified as it entered a more favorable thermodynamic environment and numerous circulations began to show up in KRAX velocity data.

At 1420Z (920AM) a tornado warning was issued until 1500Z (1000AM) for a cell showing rotation in southwest Sampson County. In addition to this cell, another smaller cell was also showing signs of rotation in northern Sampson County. However, the cell in southwest Sampson County was better organized and appeared to have a hook in the 0.9 degree reflectivity. Indeed, the smaller circulation dissipated and the circulation that prompted the warning intensified and tightened up in northern Sampson County by 1437Z. At this time, base velocities increased to 108 knots inbound! A tornado warning was issued for Johnston County at 1439Z, effective until 1530z, as the intense circulation continued moving north. As the cell crossed the border into Johnston County at 1445Z it further intensified, sporting 65 knots inbound and 40 knots outbound, gate-to-gate in 0.9 degree storm-relative velocity data. Base velocity data at 0.9 degrees showed the circulation now contained inbound velocities of up to 125 knots ! A hook echo also showed up in reflectivity imagery at 1445Z. The cell continued moving north, eventually weakening by the time it reached northern Johnston County. Funnel cloud reports were received with this cell as it crossed Highway 70 and Interstate 95 near Selma in central Johnston County.

At approximately 1544Z (1044AM) another cell developed strong rotation in Duplin County. The cell continued to show rotation as it moved northeast towards Wayne County. At 1557Z a tornado warning was issued for Wayne County, effective until 1130z. The strong circulation subsequently moved almost directly over the same portion of the County that had been affected by a supercell 3 hours earlier. The storm knocked several trees down in the Walnut Creek area as it moved northeast through Wayne County.

At 1556Z (1056AM), a cell in Nash County intensified with a VIL of 35-40 kg/m2, 60-65 dBZ max reflectivities and echo tops of 46,000 feet. The intensity of this cell, in addition to 60-70 knot outbound velocities at 2-3 kft prompted a severe thunderstorm warning for Nash County at 1102Z, effective until 1115Z. The storm knocked a tree down at 1110Z on the entrance ramp to highway 64 near Spring Hope in northeast Nash County. Since the storm had a history and continued to show a relatively strong updraft/downdraft juxtaposed with 60-70 knot outbound velocities, a severe thunderstorm warning was issued for Halifax County at 1114Z, effective until 1145Z. Reports of trees down in Enfield were received at 1125Z as the storm moved northeast through Halifax County.



Mesoscale Data

Analyzed mean sea level pressure (black) and surface wind barbs from SPC at 13Z on Thursday, November 16, 2006 (700 AM EST).
A cold front can be seen stretching southeast across western North Carolina into eastern South Carolina. A strong southeasterly wind flow is shown over central and eastern North Carolina.

SPC Analysis at 13Z on Thursday, November 16, 2006.



Analyzed surface temperature (red), surface dewpoint temperature (green), and surface wind barbs from SPC at 13Z on Thursday, November 16, 2006 (700 AM EST).
A sharp gradient in both temperatures and dewpoints can be seen across North Carolina with a maximum of both across the southern and eastern coastal areas.

SPC Analysis at 13Z on Thursday, November 16, 2006.



300 MB wind barbs (black), 300 MB isotachs (blue) and analyzed 300 MB divergence (purple) from SPC at 13Z on Thursday, November 16, 2006 (700 AM EST).
Note the 120 to 130 knot jet max located across northern Georgia, western North Carolina, eastern Tennessee, and western Virginia with a large area of divergence and implied upward vertical motion is located across eastern North Carolina.

SPC Analysis at 13Z on Thursday, November 16, 2006.



Lifting Condensation Level (green) from SPC at 13Z on Thursday, November 16, 2006 (700 AM EST).
The LCL (Lifting Condensation Level) is the level at which a parcel becomes saturated. It is a reasonable estimate of cloud base height when parcels experience forced ascent. Note that much of central and eastern North Carolina has LCL values between 500 and 750 meters.

SPC Analysis at 13Z on Thursday, November 16, 2006.



Analyzed mixed layer convective available potential energy (MLCAPE) (red) and mixed layer based convective inhibition (MLCIN) (blue lines - shaded) from SPC at 13Z on Thursday, November 16, 2006
MLCAPE values range from around 250 J/kg across the Piedmont of North Carolina to around 500 J/kg across the southern Coastal Plain and far eastern Sandhills.

SPC Analysis at 13Z on Thursday, November 16, 2006.



Analyzed Storm Relative Helicity (SRH) in the 0-3 km layer (light blue, blue, and dark blue) from SPC at 13Z on Thursday, November 16, 2006 (700 AM EST).
Note the axis of greatest SRH across central North Carolina in the eastern Piedmont and western coastal plain. The SRH is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and it is calculated for the lowest 3-km layers above ground level.

SPC Analysis at 13Z on Thursday, November 16, 2006.



NWS Composite Reflectivity Imagery from 1332Z on Thursday, November 16, 2006 (732 AM EST).
The composite reflectivity imagery is from the approximate time in which the analysis imagery above is valid.

Composite Reflectivity Imagery from 1332Z on Thursday, November 16, 2006.




Surface Analysis

A Java Loop of surface analysis imagery from 06Z (100 AM EST) on Wednesday, November 15 through 06Z (100 AM EST) Friday, November 17, 2006 is available here. The loop shows the development of storm system across the lower Mississippi Valley and its progression across the Tennessee and Ohio Valleys. The passage of the squall line and cold front responsible for the severe weather across North Carolina can also be seen.

The 15Z (1000 AM EST) surface analysis map shows the cold front approaching central NC with the parent surface low located back across West Virginia.

Surface analysis from 12Z (800 AM EST) Wednesday, June 14, 2006



Satellite

A Java Loop of infrared satellite imagery from 0325Z (1025 PM EST) through 1825Z (125 PM EST) Thursday, November 16, 2006 is available here.

The infrared satellite image below from 1145Z (645 AM EST) shows an intense thunderstorm just north of Wilmington, NC. This thunderstorm was responsible for producing the killer tornado in Columbus County NC just after 630 AM.

Infrared satellite imagery




A Java Loop of visible satellite imagery from 1255Z (755 AM EST) through 2045Z (345 PM EST) Thursday, November 16, 2006 is available here.

The visible satellite image below from 1355Z (855 AM EST) shows the multiple lines of convection across the Carolinas and the "rough" texture of the enhanced tops associated with the strongest thunderstorms.

Infrared satellite imagery



Regional Radar Loop

A Java Loop of regional reflectivity imagery from 101Z (801 PM EST) Wednesday, November 15 through 1901Z (201 PM EST) Thursday, November 16, 2006 is available here.
Note - this loop includes 38 frames.

The regional reflectivity image below is from 06281Z (128 AM EST) on Thursday, November 16, 2006 when the initial squall line was approaching central North Carolina.

regional reflectivity image



KRAX Radar Loops

First round of severe weather which primarily affected the Western Piedmont
Java Loop of KRAX reflectivity imagery from 0533Z (1233 AM EST) through 1019Z (519 AM EST) Thursday, November 16, 2006.
Note - this loop includes 61 frames)

Second round of severe weather, including the killer tornado in Columbus County, NC
Java Loop of KRAX reflectivity imagery from 1129Z (629 AM EST) through 1400Z (900 AM EST) Thursday, November 16, 2006.
Note - this loop includes 34 frames)

Third round of severe weather, including the funnel cloud reports near Highway 70 and Interstate 95 near Selma in central Johnston County
Java Loop of KRAX reflectivity imagery from 1400Z (900 AM EST) through 1659Z (1159 AM EST) Thursday, November 16, 2006.
Note - this loop includes 43 frames)

Overview of the entire event with images from every half hour between 1158 PM Wednesday and 259 PM Thursday.
Java Loop of KRAX reflectivity imagery from 0458Z (1158 PM EST) Wednesday, November 15 through 1959Z (259 PM EST) Thursday, November 16, 2006.
Note - this loop includes 31 frames

The KRAX reflectivity image below is from 0642Z (642 AM EST) on Thursday, November 16, 2006 just after the killer tornado in Riegelwood, Columbus County, North Carolina struck.





Case study team -
Brandon Vincent
Jonathan Blaes

For questions regarding the web site, please contact Jonathan Blaes.


  • NWS Disclaimer.