November 15, 2008 North Carolina Tornado Outbreak

Event Summary
National Weather Service, Raleigh NC

November 15, 2008 North Carolina Tornado Outbreak
Updated 2011/02/01

Collage of images related to this event

Event Headlines -
...Tornadoes first touched down in Calhoun and Dillon Counties in SC and then in Robeson County, NC before moving into the NWS Raleigh County Warning Area....
...An EF-2 tornado touched down in northern Johnston County just southeast of Kenly killing one person and injuring two others. Emergency management officials reported that 40 homes were damaged in Johnston County including 9 which were destroyed...
...An EF-3 tornado occurred in Wilson County near Wilson and Elm City killing one person and injuring four others. Emergency management officials reported that 26 homes were damaged in Wilson County including 7 which were destroyed. It was the second EF-3 strength tornado to occur in central North Carolina in 2008...
...The tornadoes that struck central NC were a result of a complex interaction between two separate supercell thunderstorms. The circulations associated with the two mesocyclones engaged in an intricate evolution whereby the circulations approached one another, spiraled about each other cyclonically and ultimately merged into one coherent vortex...
...This is the second killer tornado event in central North Carolina this year. The other occurrence was the May 8, 2008 tornado event in Guilford and Forsyth Counties...
...North Carolina has the largest percentage of tornado deaths that occur at night and the largest percentage of deadly nighttime tornado events...

Event Overview -
A warm front moved inland from the coast and brought about an abrupt change from cool and damp to warm and humid conditions across central North Carolina on the evening of Friday, November 14th. The interaction of this warm front with strengthening winds aloft provided favorable lift and wind shear for severe thunderstorms across the Carolinas.

Event Details -
On Friday, November the 14th, the upper flow pattern across the continental United States was characterized by an amplifying northern stream (polar) trough over the central U.S., with a cutoff but progressive southern stream upper low that was beginning to de-amplify and lift northeastward along the Gulf Coast. Meanwhile, a strong sub-tropical jet aloft extended across Mexico northeastward into the southeastern U.S., where it merged with a southern stream (polar) jet associated with the de-amplifying upper low along the Gulf Coast.

At the surface, a cold front extended from a low over eastern Ontario southwestward through the western Great Lakes and mid-Mississippi Valley to central Texas. A separate surface low, associated with the southern stream shortwave trough, was located over the northern Gulf of Mexico. A coastal front, which separated a very warm and moist maritime air mass to the southeast from a cooler cold-air damming wedge air mass over interior portions of Georgia, the Carolinas, and Virginia, extended from the northern Gulf low northeastward through southern Alabama, south central Georgia, and the eastern Carolinas.

Frontogenetical low level forcing, isentropic lift atop the low level frontal zone, and an area of divergence aloft in the exit region of a sub-tropical jet streak, led to the northeastward expansion of a broad, elongated shield of precipitation over central North Carolina during the day Friday. The precipitation diabatically cooled and further moistened the wedge air mass, and resultantly kept the coastal front pinned along the immediate coastal areas of the Carolinas throughout the day. The lead sub-tropical jet streak and shield of rain had lifted into Virginia by late Friday afternoon, and only a few spotty showers lingered over North Carolina during the evening hours. Meanwhile, the exit region of a secondary sub-tropical jet streak had nosed into southeastern US from the Gulf. The forcing for ascent from the sub-tropical jet streak, coincident with the approach of large-scale (QG) forcing for ascent attendant the de-amplifying southern stream trough, initiated multiple clusters of thunderstorms across Alabama and Georgia on Friday afternoon.

The thunderstorms developing across southwestern Georgia on Friday afternoon moved northeast as a broken line reaching southwestern South Carolina a few hours after sunset. These thunderstorms produced an EF-1 tornado in Calhoun County, SC at 0350 UTC on Friday, November 14, 2008. The thunderstorms then moved northeast producing an EF-2 tornado in Dillion County, SC at 0550 UTC. A tornado watch was issued for much of central and eastern North Carolina at 0525 UTC, a little over an hour before the first tornado touched down in North Carolina (an EF-0 tornado in Robeson County, NC at 0635 UTC). In all, there were 7 confirmed tornadoes in North Carolina that night resulting in two deaths and more than a half dozen injuries.

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

Map of tornado tracks across NC on November 15, 2008

Map of tornado tracks across NC on November 15, 2008

The Clement EF-0 Tornado

The National Weather Service, in conjunction with Sampson County Emergency Management, determined that an EF-0 tornado touched down in Western Sampson County around the Clement community. The tornado damage track was discontinuous along an approximately four-mile path that extended from Carroll Store Road just south of Maxwell Road, across Maxwell Road, through several properties between Hayes Mill Road and Baptist Chapel Road east of the community of Hays Mill, to just north of Baptist Chapel Road west of State Road 1452.

The most significant damage was concentrated at a dwelling along Maxwell Road, where trees were snapped, a carport was blown and twisted into trees, and shrubs were pulled from the ground. Much of the damage was consistent with straight-line wind damage. However, the degree of damage at the dwelling on Maxwell Road, the number of snapped trees aloft, and sporadic indication of tree damage perpendicular to the track of the tornado would indicate the likelihood of a tornado. Fortunately, there were no injuries reported. Estimated width of the tornado was 50 yards.

Time/Date: 215 AM to 230 AM Saturday November 15, 2008
Tornado: EF-0
Peak wind: 70 mph
Path length: 4 miles
Injuries: 0
Fatalities: 0

The storm damage surveyed just east of Dunn in far Northern Sampson County, along the Harnett Dunn Highway, was coincident with straight line wind damage. In a concentrated area just west of Green Path Road, there were a few instances of minor tree damage, with a couple of the trees and limbs noted to be at least a foot in diameter. Wind speeds were estimated around 60 mph.

Special thanks are extended to Sampson County Emergency Services for assistance during this survey.

Clement Tornado Track -

Clement Tornado Damage Photos -

Photos courtesy of the National Weather Service.
(click on the image to enlarge)

Photo courtesy of National Weather Service - Click to enlarge

Clement Tornado Radar Imagery -

The thunderstorm and low level circulation that produced the Clement tornado was the same storm that produced an EF-2 tornado in Dillion County, SC at 1250 AM EST and then an EF-0 tornado just east of St. Pauls, in Robeson County, NC at around 135 AM EST. The thunderstorm maintained a low level circulation and reflectivity structure as it moved out of South Carolina, into North Carolina, and finally into the southeastern portions of the NWS Raleigh County Warning Area between around 0630 UTC and 0930 UTC (130 AM and 430 AM EST).

The radar image below from the KRAX radar at 0720 UTC contains the storm relative velocity data in the top row and the base reflectivity data in the bottom row. The data in the first column is from the 0.5 degree elevation angle and the data in the second column is from the 0.9 degree elevation angle. The low and mid level circulation was broad with the inbound/outbound velocities separated by some distance. The storm relative velocity data indicated an outbound velocity of 32 knots and an inbound velocity of 40 knots producing a rotational shear value of 36 knots. The 36 knots of rotational shear at 32 nm from the radar with a mesocyclone diameter of around 2 nm corresponds to a moderate mesocyclone.

A loop of the KRAX base reflectivity imagery from 0706 UTC through 0734 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 0706 UTC through 0734 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX base reflectivity imagery from 0706 UTC through 0734 UTC November 15, 2008 - click to enlarge

A loop of the KRAX storm relative velocity imagery from 0706 UTC through 0734 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 0706 UTC through 0734 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX storm relative velocity imagery from 0706 UTC through 0734 UTC November 15, 2008 - click to enlarge

Clement Tornado Warning Products -

145 AM EST Severe Thunderstorm Warning issued for southeastern Cumberland and northwestern Sampson Counties (map of the Severe Thunderstorm Warning polygon). The warning mentions Falcon which is just a few miles north of Clement. This was the first warning issued for this event.

201 AM EST Severe Thunderstorm Warning update mentions that the storm would likely impact Stedman, Autryville, and Falcon.

Clement Tornado Warning Verification -

The Severe Thunderstorm Warning was issued at 145 AM EST and valid through 230 AM EST.
The tornado touched down at 215 AM EST.
The lead time from the Severe Thunderstorm Warning was 30 minutes.
Although a tornado warning was not in effect at the time of the tornado touchdown, the Severe Thunderstorm Warning mentioned that "severe thunderstorms can produce tornadoes with little or no advance warning."

The Meadows EF-1 Tornado

The National Weather Service found that an EF-1 tornado touched down in southwestern Johnston County just south of Blackman Crossroads at 240 AM EST. The tornado damage track was approximately 50 yards wide and extended north-northwest for approximately one mile.

The tornado initially touched down just off Noah Road, where there were several uprooted trees. it traveled north-northwest across bare fields with scattered mature trees for about one half mile and crossed Wood Crossroads, producing significant roof damage to one double-wide mobile home and tearing the porch off a substantial brick single-level home. There were several mature trees that had been twisted off at mid and upper reaches as well.

The tornado then continued north-northwest across open fields before producing minor damage on Five Points Road to the aluminum skirt of a double-wide mobile home and other minor damage to sheds and storage buildings. There was also some tree damage in this area which knocked down power lines.

Time/Date: 240 AM to 245 AM EST, Saturday November 15, 2008
Peak Wind: 90 mph
Path Length: 1 mile
Path Width: 50 yards
Injuries: none
Fatalities: none

Meadows Tornado Track -

Meadows Tornado Damage Photos -

Photos courtesy of the National Weather Service.
(click on the image to enlarge)

Meadows Tornado Radar Imagery -

The thunderstorm and low level circulation that produced the Meadows tornado also produced the Clement tornado in Sampson County. While the Meadows tornado was a short-lived EF-1 tornado with peak winds of 90 MPH, it is remarkable in that the circulation was moving north-northwestward with a second and intensifying circulation rapidly advancing northeastward behind the storm associated with the Meadows tornado.

The radar image below from the KRAX radar at 0738 UTC contains the storm relative velocity data in the top row and the base reflectivity data in the bottom row. The data in the first column is from the 0.5 degree elevation angle and the data in the second column is from the 0.9 degree elevation angle. The low level circulation was rather broad with the storm relative velocity data indicating an outbound velocity of 28 knots and an inbound velocity of 32 knots producing a rotational shear value of 30 knots. The 30 knots of rotational shear at 20 nm from the radar with a mesocyclone diameter of around 1.5 nm corresponds to a weak to moderate mesocyclone.

A loop of the KRAX base reflectivity imagery from 0724 UTC through 0806 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 0724 UTC through 0806 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX base reflectivity imagery from 0724 UTC through 0806 UTC November 15, 2008 - click to enlarge

A loop of the KRAX storm relative velocity imagery from 0724 UTC through 0806 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 0724 UTC through 0806 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX storm relative velocity imagery from 0724 UTC through 0806 UTC November 15, 2008 - click to enlarge

Meadows Tornado Warning Products -

228 AM EST Tornado Warning issued for northwestern Sampson and eastern Johnston Counties (map of the Tornado Warning polygon). The warning mentions Four Oaks which is very close to the Meadows community. This was the first tornado warning issued for this event.

243 AM EST Tornado Warning update clears Sampson County as the storm had moved out of the county. The update mentioned the two tornadic circulations on radar located in southeastern Johnston County.

258 AM EST Tornado Warning update mentions that damage has been reported in Sampson and Johnston Counties including damage to homes.

Meadows Tornado Warning Verification -

The Tornado Warning was issued at 228 AM EST and valid through 315 AM EST.
The tornado touched down at 240 AM EST.
The tornado lead time was 12 minutes.

The Pine Level EF-0 Tornado

The National Weather Service, conducted a second survey of the Pine Level community investigating some additional damage reports from the area. The survey concluded that a weak EF-0 tornado with winds between 70 to 80 mph tracked just south of Pine Level in Johnston County.

The tornado initially touched down near Daughtry Road south of U.S. 70 damaging several Pine Trees and causing minor roof damage. The tornado tracked northeast crossing Crocker Road where a car was smashed when a large carport collapsed. A travel trailer was overturned and a nearby home suffered shingle and siding damage. Continuing northeast, the tornado crossed Creech's Mill Road just south of Highway 70. Several homes suffered significant loss of shingles and siding. Three homes also had their chimneys destroyed by the wind. On the east side of Creechs Mill Road, a local horse farm had one small barn destroyed. A 30 foot horse trailer was also blown over and two large bay doors were blown in on the stables.

The tornado then crossed U.S. 70 near Stevens Chapel Road. Damage occurred in areas just north and south of the intersection of U.S. 70 and Stevens Chapel Road. Twenty four trees in a concentrated area just north of U.S. 70 were either snapped in half or uprooted. One resident, who was at home when the tornado struck, stated the tornado hit at exactly at 305 AM EST. As the tornado continued northeast it crossed country store road damaging numerous trees and outbuildings. The wind from the tornado broke a garage window of one dwelling and blew out a garage door. Further north, along Country Store Road, there was evidence of mostly minor tree damage, shingle damage, and metal roofing torn from rooftops.

An eyewitness in the area of Country Store Road also reported the sound of strong wind as the storm hit. Fortunately, there were no reported injuries.

Time/Date: 303 AM to 306 AM EST, Saturday November 15, 2008
Peak wind: 75 mph
Path Length: Approximately 3 miles
Path Width: 30-50 yards
Injuries: none
Fatalities: none

Pine Level Tornado Track -

Pine Level Tornado Damage Photos -

Photos courtesy of the National Weather Service.
(click on the image to enlarge)

Pine Level Tornado Radar Imagery -

The thunderstorm that produced the Pine Level Tornado rapidly intensified as it moved across Johnston County. This can be seen in the increase in the height of the 50-55 dBZ core aloft (from 18 to 25 thousand feet) and the development of 65 to 70 dBZ reflectivity returns in the mid levels of the storm. As the updraft intensified, the rotational velocity of the low level mesocyclone increased as well. This can be seen in the 0752 UTC storm relative velocity product, in the 0756 UTC storm relative velocity product, and the 0801 UTC storm relative velocity product.

The radar image below from the KRAX radar at 0801 UTC contains the storm relative velocity data in the top row and the base reflectivity data in the bottom row. The data in the first column is from the 0.5 degree elevation angle and the data in the second column is from the 0.9 degree elevation angle. The low level circulation increased dramatically preceding the tornado touchdown and at 0801 UTC the 0.5 degree storm relative velocity data indicated an outbound velocity of 61 knots and an inbound velocity of 32 knots producing a rotational shear value of 46.5 knots. The VR Shear calculation provided a rotational shear value of 44.8 knots and a VR Shear value of 0.0251/s at 16 nm from the RDA. The 46.5 knots of rotational shear at 16 nm from the radar with a mesocyclone diameter less than 1 nm corresponds to a moderate to strong mesocyclone.

A loop of the KRAX base reflectivity imagery from 0738 UTC through 0815 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 0738 UTC through 0815 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX base reflectivity imagery from 0738 UTC through 0815 UTC November 15, 2008 - click to enlarge

A loop of the KRAX storm relative velocity imagery from 0738 UTC through 0815 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 0738 UTC through 0815 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX storm relative velocity imagery from 0738 UTC through 0815 UTC November 15, 2008 - click to enlarge

Pine Level Tornado Warning Products -

228 AM EST Tornado Warning issued for northwestern Sampson and eastern Johnston Counties (map of the Tornado Warning polygon). The warning mentions Pine Level. This was the first tornado warning issued for this event.

243 AM EST Tornado Warning update clears Sampson County as the storm moved out of the county. The update mentioned the two tornadic circulations on radar located in southeastern Johnston County.

258 AM EST Tornado Warning update mentions that damage has been reported in Sampson and Johnston Counties including damage to homes. Noted that the storm will track just south of Interstate 95 and move very close to Pine Level and Kenly.

Pine Level Tornado Warning Verification -

The Tornado Warning was issued at 228 AM EST and valid through 315 AM EST.
The tornado touched down at 303 AM EST.
The tornado lead time was 35 minutes.

The Kenly EF-2 Tornado

The National Weather Service, in conjunction with Johnston County Emergency Management, determined that an EF-2 tornado touched down in northern Johnston County just southeast of the town of Kenly. The tornado damage track was about 150 feet wide and stretched for approximately 4.5 miles into southwestern Wilson County. The tornado initially touched down around 310 AM just north of Piney Grove Church Road, and damage was limited to minor tree and structural damage. The tornado then tracked northeast, over bare fields and stands of mature trees for about three quarters of a mile, twisting off mature trees, before producing significant damage at the intersection of NC Highway 222 and Crumpler Road.

The strongest evidence of EF-2 damage was at this intersection, where a well-constructed single level brick home was destroyed. The entire roof was blown off this home, a large pine tree fell through the center of the house (fortunately into the kitchen area), and all walls on the west side of the house were missing. In addition, one vehicle was flipped upside down and another, with an attached trailer, was moved approximately 30 feet down the driveway of the home. The family of 4 was awakened as the damage occurred, but by great fortune, none sustained any injury.

As the tornado crossed Scott Road, a double-wide mobile home was removed from its foundation and flipped approximately 50 feet. A 61 year old female occupant of this mobile home was killed, while her husband was transported to a medical facility. In addition, three other double-wide mobile homes were condemned as they sustained significant structural damage to roofs and southwest-facing exterior walls. In addition, a pickup truck was completely overturned in one of the driveways.

Continuing northeast, the tornado moved across the Kenly International Airport. The tornado was likely aloft at this point, producing EF-1 damage to trees, but there was considerable debris from the homes on Scott Road strewn about the airport grounds. A portion of an open aircraft hangar constructed of sheet tin over a wooden frame was twisted and destroyed. There was also some damage to the Cessna 150 housed in this hangar.

The tornado then crossed into southwest Wilson County causing damage to several homes along Fabwhitley Road. EF-1 damage occurred here, with considerable damage to a home where a carport and extension were destroyed and blown to the northeast. Fortunately, there were no known injuries in the home.

Several other homes in the Lucama area suffered minor damage from the strong winds. The tornado finally lifted off the ground just north of Newsom Mill Road near a local racetrack. In this location, across the road from the racetrack, a mobile home was rolled to the south.

Time/Date: 310 AM - 315 AM EST Saturday November 15, 2008
Tornado:EF-2
Peak Wind: 135 mph
Path Length: 4.5 miles (approximately 2 miles in northern Johnston County and 2.5 miles into southwestern Wilson County.
Injuries: 2
Fatalities: 1

Special thanks are extended to Johnston County Emergency Services and the Kenly Fire Department for assistance during this survey and for providing access to the damaged areas.

Kenly Tornado Track -

Kenly Damage Photos -

Photos courtesy of the National Weather Service.
(click on the image to enlarge)

Kenly Tornado Radar Imagery -

The radar image below from the KRAX radar at 0815 UTC contains the storm relative velocity data in the top row and the base reflectivity data in the bottom row. The data in the first column is from the 0.5 degree elevation angle and the data in the second column is from the 0.9 degree elevation angle. The low level circulation increased dramatically preceding the tornado touchdown and at 0815 UTC the 0.5 degree storm relative velocity data indicated an outbound velocity of 58 knots and an inbound velocity of 47 knots producing a rotational shear value of 52.5 knots. The VR Shear calculation provided a rotational shear value of 52 knots and a VR Shear value of 0.0909/s at 20 nm from the RDA. The 52 knots of rotational shear at 20 nm from the radar with a mesocyclone diameter less than 1 nm corresponds to a strong mesocyclone with the VR Shear value of 0.0909/s corresponding to a "Tornado Possible" based on guidance from the Rotational Shear Nomogram for Tornadoes.

A loop of the KRAX base reflectivity imagery from 0801 UTC through 0833 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 0801 UTC through 0833 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX base reflectivity imagery from 0801 UTC through 0833 UTC November 15, 2008 - click to enlarge

A loop of the KRAX storm relative velocity imagery from 0801 UTC through 0833 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 0801 UTC through 0833 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX storm relative velocity imagery from 0801 UTC through 0833 UTC November 15, 2008 - click to enlarge

Kenly Tornado Warning Products -

228 AM EST Tornado Warning issued for northwestern Sampson and eastern Johnston Counties (map of the Tornado Warning polygon). The warning mentions Pine Level and Kenly. This was the first tornado warning issued for this event.

243 AM EST Tornado Warning update clears Sampson County as the storm had moved out of the county. The update mentioned the two tornadic circulations on radar located in southeastern Johnston County.

308 AM EST Tornado Warning issued for north-central Wayne, east-central Johnston, and Wilson Counties (map of the Tornado Warning polygon). The warning mentions Kenly, Lucama, Wilson and Elm City.

319 AM EST Tornado Warning update clears Johnston and Wayne Counties since the storm has moved out of the counties.

Kenly Tornado Warning Verification -

The Tornado Warning was issued at 228 AM EST and valid through 315 AM EST.
The tornado touched down at 310 AM EST.
The tornado related fatality occurred just after 310 AM EST.
The tornado lead time was 42 minutes and the lead time preceding the fatality was just over 42 minutes.

The Elm City EF-3 Tornado

The National Weather Service, in conjunction with Wilson County Emergency Services and Wilson Fire and Rescue, determined that an EF-3 tornado occurred in Wilson County on November 15, 2008. The tornado occurred along a discontinuous, approximately eight-mile path that began with minor roof damage to a dwelling and a snapped tree along Harrison Drive just south of Ward Boulevard in Wilson. The most significant damage was then noted to the northeast, along London Church Road, south of NC Route 1330.

On London Church Road, one home was completely destroyed and swept off of its foundation. Based on eyewitness accounts and the damage, fire and rescue officials estimate that the home rolled as many as four times. In this home, there was unfortunately one fatality, an 11 year-old, and two injuries.

Across the road from this home to the northeast, the upper portion of a home was destroyed, and another home had a roof completely blown away with trees on top of it. In this latter home, eyewitness accounts noted there were two more injuries. Other eyewitness accounts suggested there was little noise with the event until the tornado struck. Several individuals were awake for various reasons around 330 AM, and it was just a few minutes after this time when the tornado struck the London Church Road area.

The tornado then followed a discontinuous path into Elm City. There were numerous indications of tree damage in Elm City with a porch roof blown off, and outbuildings damaged or toppled. Finally, the last noticeable damage was observed along NC Route 1400, and just north of the intersection of Hefner Road and NC Route 1402, where small clusters of trees were snapped and outbuildings were damaged. The damage in and northeast of Elm City was consistent with EF-0 damage.

Time/Date: Estimated from 330 AM to 345 AM EST, Saturday November 15, 2008
Peak Wind: 140 mph
Path Length: Approximately 8 miles discontinuous
Path Width: 100 yards
Injuries: 4 known
Fatalities: 1

Elm City Tornado Track -

Elm City Damage Photos -

Photos courtesy of the National Weather Service.
(click on the image to enlarge)

Elm City Tornado Radar Imagery -

The thunderstorm that produced the Elm City Tornado moved through Kenly about 15 minutes prior to spawning the Elm City Tornado. In fact, the low level rotation associated with the Kenly storm had weakened as seen in 0824 UTC storm relative velocity imagery. A second low level circulation center (storm B) appears to have been ingested or merged into the mesocyclone that would produce the Elm City tornado as seen in the storm relative velocity imagery at 0829 UTC.

The radar image below from the KRAX radar at 0833 UTC contains the storm relative velocity data in the top row and the base reflectivity data in the bottom row. The data in the first column is from the 0.5 degree elevation angle and the data in the second column is from the 0.9 degree elevation angle. At 0833 UTC, the 0.5 degree storm relative velocity data indicated an outbound velocity of 33 knots and an inbound velocity of 79 knots producing a rotational shear value of 56 knots. The VR Shear calculation provided a rotational shear value of 55.5 knots and a VR Shear value of 0.1216/s at 29 nm from the RDA. The 56 knots of rotational shear at 29 nm from the radar with a mesocyclone diameter less than 1 nm corresponds to a strong mesocyclone with the VR Shear value of 0.1216/s corresponding to a "Tornado Possible" based on guidance from the Rotational Shear Nomogram for Tornadoes.

A loop of the KRAX base reflectivity imagery from 0819 UTC through 0847 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 0819 UTC through 0847 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX base reflectivity imagery from 0819 UTC through 0847 UTC November 15, 2008 - click to enlarge

A loop of the KRAX storm relative velocity imagery from 0819 UTC through 0847 UTC November 15, 2008 is shown below. A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 0819 UTC through 0847 UTC November 15, 2008 is available here. Note - this loop includes 8 frames

Loop of the KRAX storm relative velocity imagery from 0819 UTC through 0847 UTC November 15, 2008 - click to enlarge

Elm City Tornado Warning Products -

308 AM EST Tornado Warning issued for north-central Wayne, east-central Johnston, and Wilson Counties (map of the Tornado Warning polygon). The warning mentions the communities of Kenly, Lucama, Wilson and Elm City.

319 AM EST Tornado Warning update mentions the communities of Wilson and Elm City are in the path of the tornado. The update also mentions that strong rotation was indicated by radar.

329 AM EST Tornado Warning update reported a tornado on the ground near Lucama. The update mentions the communities of Wilson and Elm City.

Elm City Tornado Warning Verification -

The Tornado Warning was issued at 308 AM EST and valid through 400 AM EST.
The tornado touched down at 330 AM EST.
The tornado related fatality occurred at 338 AM EST.
The tornado lead time was 22 minutes and the lead time preceding the fatality was 30 minutes.

Radar and Storm Scale Analysis

The tornadoes that struck central North Carolina were a result of a complex interaction between two separate supercell thunderstorms. The circulations associated with the two mesocyclones then underwent an intricate evolution whereby the circulations approached one another in a spiral, cyclonic (in a relative sense) orbit, and ultimately merged into one coherent vortex.

Storm relatively velocity loop from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 - click on the image to enlarge

The initially easternmost storm (Storm A, hereafter), produced the first tornado damage (EF-0) as it tracked northeastward through the Clement community in western Sampson County at 215 AM. At that time, a separate northeast-bound storm (Storm B, hereafter) was located approximately 10 miles to the west northwest of Storm A. Storm B continued northeastward and began to gain strength near the county border of Harnett and Sampson, where it produced straight-line wind damage just east of the city of Dunn. Meanwhile, Storm A assumed a more northward course into southern Johnston County, and produced EF-1 tornado damage along a north northwestward track through the town of Meadows. Storm A subsequently weakened as it continued northward and crossed in front of the path of Storm B.

The updraft of Storm B rapidly intensified as it tracked across Johnston County, which can be inferred by both a rapid increase in the height of the 50-55 dBZ core at storm summit (from 18 to 25 kft) and the development of 65 to 70 dBZ in the mid levels of the storm (between 15 and 19 kft). The inferred vertical velocity associated with the strengthening updraft presumably stretched and �spun-up� the low level vorticity, thereby increasing the rotational velocity of the low level mesocyclone. Storm B subsequently produced a short lived EF-0 tornado near the Pine Level community and then EF-1 to EF-2 tornado damage northeastward on a discontinuous path through Kenly. Meanwhile, Storm A continued on a northward track, and had moved to the northwest of tornadic Storm B by the time Storm B reached Kenly. Though the low level rotation of Storm A had dramatically weakened, the mid level mesocyclone maintained rotational velocities in excess of 30 knots as it continued to cyclonically orbit and approach Storm B.

Base reflectivity loop from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 - click on the image to enlarge

The rotational shear in Storm B weakened as the storm moved northeast of Kenly and the tornado damage stopped well southwest of Lucama. As Storm B approached Wilson, the remnant circulation of Storm A which was still apparent a mid levels converged on the southwest side of Storm B. The circulation of Storm A then merged with Storm B just as the Elm City tornado touched down northeast of Wilson. The mesocylone of the combined Storm A/B increased dramatically northeast of Wilson with rotational velocities in excess of 55 knots likely corresponding to the EF-3 damage on London Church Road. The mesocyclone weakened northeast of Elm City and the tornado dissipated.

The images above and to the right are from the NWS Raleigh KRAX WSR-88D Doppler radar located near Clayton, North Carolina or about 10 miles southeast of Raleigh. The loop begins at 0643 UTC (143 AM EST) and continues through 0847 UTC (347 AM EST) on Saturday, November 15, 2008.

In the four-panel storm relative velocity loop, the image in the upper left is from the 0.5 degree elevation angle, the upper right is the 0.9 degree elevation angle, the lower right is from the 1.3 degree elevation angle and the lower left is from the 1.8 degree elevation angle. The storm motion ranges around 50kts from 215 to 220 degrees. The green colors depict storm relative velocities toward the radar which is in the upper left of the image.

Base velocity loop from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 - click on the image to enlarge

A Java loop in which the user can stop, start, and animate the imagery of KRAX base storm relative velocity data from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 is available here. Note - this loop includes 28 frames

In the four-panel base reflectivity loop, the image in the upper left is from the 0.5 degree elevation angle, the upper right is the 0.9 degree elevation angle, the lower right is from the 1.3 degree elevation angle and the lower left is from the 1.8 degree elevation angle. The blue and green colors depict lighter precipitation intensity while the yellows and reds indicate much heavier precipitation.

A Java loop in which the user can stop, start, and animate the imagery of KRAX base reflectivity data from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 is available here. Note - this loop includes 28 frames

In the four-panel base velocity loop, the image in the upper left is from the 0.5 degree elevation angle, the upper right is the 0.9 degree elevation angle, the lower right is from the 1.3 degree elevation angle and the lower left is from the 1.8 degree elevation angle. The green colors depict storm relative velocities toward the radar which is in the upper left of the image.

A Java loop in which the user can stop, start, and animate the imagery of KRAX base velocity data from 0643 UTC through 0847 UTC on Saturday, November 15, 2008 is available here. Note - this loop includes 28 frames

Comparison of Super Resolution Data and Legacy 8 Bit Data

In the spring and summer of 2008, a long term project to upgrade the resolution of several WSR-88D radar products was fielded. The improved data resolution is called super resolution. The WSR-88D data resolution before super resolution was installed was 1 degree in azimuth by 1000 m in range for reflectivity products and 1 degree in azimuth by 250 m range in range for velocity products. Super resolution data improves reflectivity and velocity resolution to 0.5-degree azimuth by 250 m range. Initially super resolution data will only be produced for �split cut� elevation angles or those elevation angles at or below around 1.5 degrees when the radar is in storm mode. Additionally, the range of the radar will be extended from 230 km to 300 km. The improved data resolution will not be used in the various radar algorithms at this point. Simulations using super resolution data show that mesocyclone and tornado signatures can be detected at greater ranges than with legacy resolution data. In addition, other smaller scale features should be detectable in base products sooner or with greater reliability. A selected comparison of super resolution and legacy 8-bit data is shown below.

Examples

The image below is a four-panel radar image from the KRAX WSR-88D valid 0801 UTC on November 15, 2008 just before the Pine Level Tornado touched down. The images on the top row are KRAX base reflectivity at 0.5 degrees while the images in the bottom row are storm relative velocity at 0.5 degrees. The reflectivity images on the left hand side are super resolution radar data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit reflectivity imagery at 1 degree and 1000 m resolution. The storm relative velocity images on the left hand side are super resolution data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit storm relative velocity imagery at 1 degree and 250 m resolution.

The improvement in the super resolution data is apparent, especially in the reflectivity data. The super resolution reflectivity imagery is very detailed when compared to the legacy reflectivity imagery while the improvement in storm relative velocity imagery is not nearly as great, since the storm relative velocity resolution was only improved from 1 degree and 250 m resolution to 0.5 degrees and 250 m resolution.

Comparison of super resolution and legacy reflectivity and storm relative velocity imagery from 0801 UTC - click to enlarge

The image below is similar to the image above with a four-panel radar image from the KRAX WSR-88D valid 0815 UTC on November 15, 2008 as the Kenly Tornado was just about to lift off the ground after producing EF-2 damage. The images on the top row are KRAX base reflectivity at 0.5 degrees while the images in the bottom row are storm relative velocity at 0.5 degrees. The reflectivity images on the left hand side are super resolution radar data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit reflectivity imagery at 1 degree and 1000 m resolution. The storm relative velocity images on the left hand side are super resolution data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit storm relative velocity imagery at 1 degrees and 250 m resolution.

Comparison of super resolution and legacy reflectivity and storm relative velocity imagery from 0815 UTC - click to enlarge

The image below is a four-panel radar image from the KRAX WSR-88D valid 0833 UTC on November 15, 2008 as the Elm City Tornado was producing damage southwest of Elm City. The images on the top row are KRAX base reflectivity at 0.5 degrees while the images in the bottom row are storm relative velocity at 0.5 degrees. The reflectivity images on the left hand side are super resolution radar data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit reflectivity imagery at 1 degree and 1000 m resolution. The storm relative velocity images on the left hand side are super resolution data at 0.5 degrees and 250 m resolution while the images on the right side are legacy 8-bit storm relative velocity imagery at 1 degrees and 250 m resolution.

Comparison of super resolution and legacy reflectivity and storm relative velocity imagery from 0833 UTC - click to enlarge

The image below is from 0833 UTC on November 15, 2008 and it compares the storm relative velocity super resolution data at 0.5 degrees and 250 m with the storm relative velocity legacy 8-bit resolution at 1 degree and 250 m. This was around the time in which the Elm City tornado was producing EF-3 damage northeast of Wilson. The super resolution storm relative velocity data was able to capture the 79 knot inbound velocity (shown in blue) while the legacy storm relative velocity product did not resolve it. This resulted in a much stronger rotational velocity value for the super resolution data which was 17 knots stronger than the rotational velocity in the legacy data.

comparison chart of the storm relative velocity super resolution and legacy data at 0833 UTC

comparison chart of the storm relative velocity super resolution and legacy data at 0833 UTC

NSSL's Rotational Track Product

Rotational track product from 03 UTC through 12 UTC combined with initial LSR reports - click on the image to enlarge

For over a decade, NOAA's National Severe Storms Laboratory (NSSL) has developed products and tools for severe weather operations in the Warning Decision Support System (WDSS). The tools are developed to assist forecasters in providing the most accurate and timely warnings of severe weather possible.

One such product is the "Rotational Tracks" product which is a gridded dataset that contains rotational shear from single and multiple radars that is accumulated over time providing tracks of radar detected rotation. The basic process for creating these products is initiated when velocity data from each radar is run through a Linear Least Squares Derivative (LLSD) filter creating an azimuthal shear field. The azimuthal shear fields in a 0-3 km layer from each radar across the CONUS are then combined and the maximum value at each 250 m² grid point is plotted over the time period providing the graphic.

The process was further improved when the WDSS-II (Warning Decision Support System - Integrated Information) group at NSSL made the "Rotational Tracks" data available for display in Google Earth. Using Google Earth with an overlay of near real-time rotational tracks allows forecasters to estimate where a storm�s low-altitude circulation was most intense and to determine locations of possible damage. The satellite images and high density maps in Google Earth often make it possible to determine the location down to a neighborhood or the street. This simplifies the verification process by reducing the amount of time that is spent searching for reports.

Rotational track product from 03 UTC through 12 UTC combined with tornado tracks - click on the image to enlarge

The first image, shown in the upper right includes the rotational track product from 0300 UTC through 1200 UTC on Saturday, November 15, 2008. The image also includes the initial NWS storm reports from LSR's overlaid with red "T" icons marking a tornado report and blue "W" icons noting a wind damage report. The shaded areas represent areas where the radar detected rotation, and the yellows and reds are indicative of the strongest rotation. It is important to note that some of the initial LSR reports can be revised after storm surveys and additional details on the exact location and time of events are collected. In addition some initial tornado reports can be revised and documented as straight line wind damage as was the case in northwestern Sampson County. Regardless, the preliminary storm reports match up extremely well with the low level rotation indicated in the rotational track product.

The second image includes the same rotational track product as above but it also includes the revised tornado track path as determined from storm surveys and other reports. The actual tornado tracks are locations where the tornado funnel actually touches the ground. These tracks are much more limited then the area in which the radar produced rotational shear data is large indicative of robust rotation in the storm with inconsistent tornado touchdowns. Despite the fairly large area of noise in the data produced from interference near the radar site, the tornado tracks match up extremely well with the low level rotation indicated in the rotational track product. This suggests that this data set can be used to refine locations where storm surveys can investigate possible tornado touchdowns.

Zooming in and looking at the data on a smaller scale, the rotational tracks data is shown in the last image with the tornado tracks superimposed. This image shows the impressive nature of this data set. An even more zoomed in image of the rotational track product for the Elm City Tornado near London Church Road where the EF-3 damage was reported is available.

To demonstrate the utility of the NSSL's Rotational Track product and other Google Earth products, the "kmz" products are available in the links below. A zip file containing the contents listed below is available in a zip file.

Nighttime Tornadoes Pose a Much Greater Threat

The November 15, 2008 tornado outbreak marked the second killer nocturnal tornado event in central North Carolina this year. On November 15th, an EF-2 tornado touched down in northern Johnston County just southeast of the town of Kenly just after 300 AM EST, killing one person and injuring two others. A short time later, an EF-3 tornado occurred in Wilson County near Elm City, killing one person and injuring four others. The other killer nocturnal tornado event in central North Carolina was the May 8, 2008 tornado event in Guilford and Forsyth Counties.

In a study of tornadoes from 1950 to 2005, Ashley et al. (2008) found that 27.3% of tornadoes were nocturnal, while 39.3% of tornado fatalities and 42.1% of killer tornado events occurred at night. In this study, nocturnal or nighttime tornadoes were defined as tornadoes with start times in local standard time (LST) that occur between the local sunset and sunrise. All of the event times used in this study were converted to LST with sunset�sunrise calculations based on the location�s LST. This is an improvement over previous studies on this subject which used a fixed time that ignored variations in latitude or the east-west location in a time zone. In addition, this study removed the issue of daylight savings time that further complicates the subject. It is important to note that nocturnal tornadoes may be underreported when compared to daytime tornadoes, especially those tornadoes that produce little property damage or that do not result in injuries or fatalities.

During the period from 1950 to 2005, Ashley et al. (2008) noted that nearly 4.9% of all �overnight� tornadoes (LST midnight to sunrise), or roughly 1 in 20 events, were killer events. Compare this to 3.6% of �evening� tornadoes (sunset to LST midnight) that were killer, and just 2.0% of �daytime� tornadoes. During the 55 year period tornadoes were nearly 2.5 times as likely to kill during the overnight hours as those during the daytime.

Various factors may explain the larger threat that nocturnal tornados pose. First, tornadoes are difficult to visually identify at night by the public, law enforcement, and trained spotters. In addition, the number of people available to potentially identify tornadoes at night is significantly reduced from the daytime. Another factor to consider is that the public is much less likely to receive a warning at night due to normal sleeping patterns (Monk et al. 2000). To further complicate things, the public has a tendency to be in more vulnerable building structures and housing, such as mobile, manufactured, or single-family homes during the night as compare to safer locations such as schools or work places in steel or reinforced-concrete buildings during the day (Simmons and Sutter 2005; Ashley 2007). Ashley (2007) found that 69.2% of all tornado fatalities from 1985 to 2005 occurred in either mobile or permanent homes, illustrating the enhanced vulnerability of these particular housing structures.

A poll from Harris Interactive (2007) found that 61% of those surveyed acquired their weather forecasts from local television news or The Weather Channel, with an additional 23% of those surveyed acquiring weather forecasts from internet sources. Acquiring weather forecasts and warnings via these sources requires the user to be awake and engaged. These sources generally do not provide a mechanism or assistance to alert users of approaching tornadoes during the overnight period. Because of this, it is expected that the vulnerability would be higher during the overnight hours when most persons are sleeping and not actively seeking warning or forecast information.

Vulnerability due to Nocturnal Tornadoes - click to enlarge

Ashley et al. (2008) found that North Carolina was ranked first with the greatest percentage of killer nocturnal tornadoes and killer nocturnal tornado events. The study found that 80.7% of tornado deaths in North Carolina occur at night with 66.7% of all killer tornado events occurring during the nighttime as well. Compare this with the fact that North Carolina receives a moderate number of nocturnal tornadoes (28.3% of all tornadoes occur at night in North Carolina). This ranking was based on a period of study from 1950 to 2005 and only includes states with a minimum of 10 killer events in order to remove small sample size effects on the percentages.

The threat that nocturnal tornadoes pose in North Carolina is obvious. One way that residents of North Carolina can receive tornado warnings in the middle of the night is via NOAA Weather Radio.

On the night of November 15, 2008, the National Weather Service was able to provide an average warning lead time of 29 minutes, well in advance of the tornado touchdowns or the occurrence of storm damage. NOAA Weather Radios across Johnston and Wilson counties sounded the alarm preceding the tornadoes. Unfortunately, many households still do not have these life saving devices. The links below provide resources to learn more about NOAA Weather Radio:

For details about NOAA Weather Radio in North Carolina, please visit www.erh.noaa.gov/rah/ncnwr/

For information on NOAA Weather radio including where to buy and how to program, please visit www.weather.gov/nwr/

November Tornadoes and the Secondary Fall Severe Weather Season

Locklear (2008) in a study of severe weather and tornadoes across WFO Raleigh�s (RAH) County Warning Area (CWA) during the period of 1950 to 2005 found that 284 tornadoes were reported in the 55 year period. All 31 counties in the RAH CWA have had at least 2 confirmed tornadoes during that time frame. On average, five tornadoes occur within the RAH CWA each year. In addition, the RAH CWA has experienced tornadoes throughout the calendar year. However, tornadoes are most likely to occur during the spring (March through May) when 43% or 122 of the total 284 tornadoes have occurred. The most active month is May when 59 of the total 284 tornadoes or 21% have been reported. Spring is the peak tornado season in the RAH CWA because of the increasing instability while the region is still vulnerable to strong and shearing winds through the depth of the atmosphere. The number of tornadoes decreases dramatically during the summer months (June through August), as the jet stream migrates north and the upper wind flow weakens over the Carolinas. There is a pronounced, secondary peak of tornadoes in the fall (September through November). This secondary tornado season can be explained by two processes, 1) land-falling tropical systems or their remnants and 2) the interaction of a strengthening wind field as the jet stream migrates south with occasional periods of instability.

Some of the notable November tornado events across central and eastern North Carolina since 1980 include...

November 15-16, 2006 Tornado Event (Riegelwood, NC)

North Carolina Tornado Outbreak, November 22, 1992

November 4, 1992 Tornado Event (southeastern NC)

Raleigh Tornado, November 28, 1988 (an F4 tornado strikes Raleigh, NC)

November 17, 1988 Tornado Event (central Coastal Plain of NC)

November 5, 1988 Tornado Event (northeastern NC)

Mesoscale Data

Forecasters at RAH routinely use the SPC meso-analysis products during severe weather operations. During this event, the SPC meso-analysis products were consulted frequently to monitor the evolving environment, anticipate the growing tornado threat, and locate the region of greatest threat. The images and discussion below highlight several of the SPC meso-analysis products that provide insight into the evolution of the severe weather event. These images are not only used in real time but they are archived locally for use in post event analysis and training.

Analyzed surface Theta-e (green contours), Theta-e convergence (purple contours) and wind barbs from SPC at 0800 UTC on Saturday, November 15, 2008
By 0800 UTC, the coastal front had advanced inland into the Coastal Plain and it can be approximated by the warm side of the Theta-e gradient near the 340 degree isentrope. A second boundary at the eastern edge of the wedge air mass was located in the western Piedmont and Foothills. The tornadoes in the RAH CWA developed in the vicinity of the coastal front between 200 and 400 AM EST and tracked northeastward. The availability of a nearby source of low level instability near the surface likely played an important role in tornadogenesis.
(Click on the image below to enlarge)

SPC Analysis at 0800 UTC on Saturday, November 15, 2008 - click to enlarge

850 mb heights, temperatures (red/blue), dew points (green), and wind barbs (black) from SPC at 0800 UTC on Saturday, November 15, 2008
An 850 mb trough was located across the central Tennesssee valley at 0800 UTC. Behind the trough, temperatures were approaching zero degrees C across western Kentucky and western Tennessee. Ahead of the trough, the low level jet axis of around 55 kts extended from near Atlanta, GA to Raleigh, NC. In fact, the winds near 850 mb at 5,000 feet as shown in the Raleigh profiler actually reached 70 kts at around 0600 UTC. Some subtle directional convergence is suggested in the 850 mb layer across eastern NC.
(Click on the image below to enlarge)

Analyzed mixed layer convective available potential energy (MLCAPE) (red) and mixed layer based convective inhibition (MLCIN) (blue lines - shaded) from SPC at 0800 UTC on Saturday, November 15, 2008
MLCAPE values ranged between 1000 and around 1500 J/kg across the central and northern Coastal Plain near the coastal front. A small area of near zero convective inhibition (CIN) overlapped the MLCAPE values greater than 1000 J/Kg in a narrow region extending northeast from Goldsboro. The region of moderate instability was favorable for intense updrafts and stretching vorticity vertically to support tornadogenesis.
(Click on the image below to enlarge)

0-6 km Bulk Shear (blue) and storm motion (brown) from SPC at 0800 UTC on Saturday, November 15, 2008
The 0-6 km bulk shear values range between 60-65 knots across the Coastal Plain. Given sufficient instability, thunderstorms tend to become more organized and persistent as vertical shear increases. Supercells are commonly associated with vertical shear values of 35-40 knots and the analysis at 0800 UTC supports the potential of supercells.
(Click on the image below to enlarge)

0-1 km Storm Relative Helicity (SRH) (shown in blue) and storm motion (brown) from SPC at 0800 UTC on Saturday, November 15, 2008
Note that the 0-1 km SRH values range between 200 and 250 m²/s² across the Coastal Plain of North Carolina. The SRH is a measure of the potential for cyclonic updraft rotation in right-moving supercells. Studies have shown that larger values of 0-1 km SRH, greater than 100 m²2/s², suggests an increased threat of tornadoes and that very large values of 0-1 km SRH (perhaps greater than 200 to 300 m²/s²) are indicative of significant tornado potential.
(Click on the image below to enlarge)

0-3 km Storm Relative Helicity (SRH) (shown in blue) and storm motion (brown) from SPC at 0800 UTC on Saturday, November 15, 2008
Note that the 0-3 Km SRH values range between 200 and 300 m²/s² across the Coastal Plain of North Carolina. The SRH is a measure of the potential for cyclonic updraft rotation in right-moving supercells. Larger values of 0-3 km SRH (greater than 100 m²/s²) suggest an increased threat of supercells and tornadoes. Some studies suggest that the 0-3 km SRH is a better indicator of storm rotation, which is related to tornadoes, but not directly the potential for tornadoes themselves.
(Click on the image below to enlarge)

Analyzed Significant Tornado Parameter (STP) (effective layer) (shown in yellow and red) and the mixed layer convective inhibition (MLCIN) from SPC at 0800 UTC on Saturday, November 15, 2008
The STP is designed to highlight areas favoring right-moving tornadic supercells. The STP is a multiple ingredient, composite index that includes effective bulk wind difference (EBWD), effective storm-relative helicity (ESRH), 100-mb mean parcel CAPE (MLCAPE), 100-mb mean parcel CIN (MLCIN), and 100-mb mean parcel LCL height (MLLCL). Analyzed values across central and eastern North Carolina show that the tornado outbreak area was highlighted in and near a region with STP values between 1 and 2. Additional details on the Analyzed Significant Tornado Parameter (STP) is available in this reference.
(Click on the image below to enlarge)

Analyzed Lifting Condensation Level (red, blue, and green) from SPC at 0800 UTC on Saturday, November 15, 2008
The LCL height is the height at which a parcel becomes saturated when lifted dry adiabatically. The importance of LCL height is thought to relate to sub-cloud evaporation and the potential for outflow dominance. Low LCL heights imply less evaporational cooling from precipitation and less potential for a strong outflow that would likely inhibit low-level mesocyclone development. Thunderstorms that produce significant tornadoes generally have a lower LCL height with LCL heights less than 1,000 meters typically favorable for tornado development. The LCL values during this event in the areas where tornadoes occurred ranged between 500 to 750 meters.
(Click on the image below to enlarge)

NWS composite radar reflectivity imagery from 0800 UTC on Saturday, November 15, 2008.
The composite reflectivity imagery is from the approximate time in which the analysis imagery above is valid.

Composite Reflectivity Imagery from 0800 UTC on Saturday, November 15, 2008 - click to enlarge

Regional Radar Loop

A Java loop of regional reflectivity imagery from 1458 UTC on November 14 through 1158 UTC on November 15, 2008 is available here. Note - this loop includes 94 frames.

The loop shows that the severe thunderstorms that produced the tornadoes across central North Carolina can be traced back to southwestern Georgia between 1800 and 1900 UTC on November 14, 2008. This area of thunderstorms produced an EF-1 tornado in southeastern Calhoun County, SC at 0350 UTC (1050 PM EST) on Friday, November 14, 2008. The thunderstorms then moved northeast producing an EF-2 tornado in Dillion County, SC at 0550 UTC (1250 AM EST) on Saturday, November 15, 2008. As the storms moved northeast, an EF-0 tornado touched down just east of St. Pauls, in Robeson County, NC at around 0635 UTC (135 AM EST) on Saturday, November 15, 2008. The severe thunderstorms then moved across eastern portions of the NWS Raleigh County Warning Area between around 0630 UTC and 0930 UTC (130 AM and 430 AM EST).

The regional reflectivity image below is from 0758 UTC on November 15, 2008. This was just a few minutes before the EF-2 tornado touched down in northern Johnston County, just southeast of Kenly.

Regional reflectivity image - click to load loop

KRAX Radar Loops

Overview of the entire event with images from every 15 minutes between 0403 UTC (1103 PM EST) through 1128 UTC (628 AM EST) on November 15, 2008.
Java loop of KRAX reflectivity imagery every 15 minutes from 0403 UTC through 1128 UTC on November 15, 2008.
Note - this loop includes 31 frames

Overview of the entire event with images from every volume scan between 0403 UTC (1103 PM EST) through 1128 UTC (628 AM EST) on November 15, 2008.
Java loop of KRAX reflectivity imagery from 0403 UTC through 1128 UTC on November 15, 2008.
Note - this loop includes 100 frames

The KRAX reflectivity image below is from 0838 UTC or 338 AM EST on Saturday, November 15, 2008, just as the tornado is moving into Elm City in Wilson County.

Archived Text Data from the Severe Weather Event

Select the desired product along with the date and click "Get Archive Data."
Date and time should be selected based on issuance time in GMT (Greenwich Mean Time which equals EST time + 5 hours).

Product ID information for the most frequently used products...

RDUAFDRAH - Area Forecast Discussion
RDUZFPRAH - Zone Forecast Products
RDUAFMRAH - Area Forecast Matrices
RDUPFMRAH - Point Forecast Matrices
RDUHWORAH - Hazardous Weather Outlook
RDUNOWRAH - Short Term Forecast
RDUSPSRAH - Special Weather Statement
RDULSRRAH - Local Storm Reports (reports of severe weather)
RDUSVRRAH - Severe Thunderstorm Warning
RDUSVSRAH - Severe Weather Statement
RDUTORRAH - Tornado Warning

from

Lessons Learned

The threat of severe weather across the Eastern Piedmont, Coastal Plain and Sandhills region was highlighted in advance of the event in the regular zone and graphical forecasts as well as the Area Forecast Discussion and the Hazardous Weather Outlook:
402 AM EST, Thursday, November 14 Zone Forecast Product
402 AM EST, Thursday, November 14 Graphical Forecasts valid 400 AM Saturday, November 15th
325 AM EST, Thursday, November 14 Area Forecast Discussion
506 AM EST, Thursday, November 14 Hazardous Weather Outlook

Just before the outbreak of severe weather, forecasters analyzed the short term mesoscale trends using a variety of tools including the SPC meso-analysis products, wind profilers, satellite imagery, and radar data to produce an excellent summary of the expected evolution of the event in the 1030 PM EST Area Forecast Discussion.

Forecasters used surface and meso-analysis throughout the warning process. The SPC meso-analysis page was invaluable and it was used frequently to find the locations that had the greatest tornado and severe thunderstorm threat.

The three ingredients needed for significant (EF-2 or greater) tornadoes, as indicated by Funk (2002) were present during the event, they include:

persistent, rotating updraft - high values of CAPE (especially in the 0-3 km layer) and SRH is favorable for the development of a significant mesocyclone the stronger the updraft and higher he SRH -

enhanced Storm-Relative Helicity (SRH) - high values of SRH in the 0-3 km and especially the 0-1 km layer are needed for a rotating updraft and the SRH values can be augmented near boundaries

special Rear Flank Downdraft (RFD) - a warm RFD with more CAPE, less CIN, and higher theta-e allows more RFD air to be ingested into the updraft and enhance low level rotation. This can be monitored by examining low level dew point depressions and LCL heights.

Calling the 911 center for each threatened county as a Tornado or Severe Thunderstorm warning was issued and then requesting that they call the NWS Raleigh back if they received damage reports was critical. The first damage reports were promptly received from Sampson County, at least in part to this strategy. The emergency services personnel were proactive and patient with our requests for information. Having quality reports early in the event increased confidence in subsequent warnings and statements.

Each warning was followed up by a Severe Weather Statement at approximately every 15 minutes. Forecasters used the Severe Weather Statement to provide updates on the tornado track and intensity.

Forecasters used various situational awareness tools to stay abreast of the unfolding event. The exchange of information (damage reports, tornado touchdowns, injuries, etc.) from emergency managers was very good. This information was supplemented by viewing local news media reports on a television monitor in the operations area.

Forecasters used Google Earth to produce accurate latitude and longitude points for the locations of the various damage reports. After getting the address or the nearest intersection from local law enforcement, the process to get the latitude and longitude points was relatively simple and easy. This can be seen in the apparent accurate placement of the damage reports in the rotational tracks product from NSSL.

The event sparked a great deal of media interest at both local and national levels. Preparing for a significant number of media calls and posting information on the event on the web site as quickly as possibly was helpful.

Nighttime tornadoes are a big threat, especially in North Carolina. NWS Raleigh will be focusing outreach activities during the coming months on the threat of severe weather at night and the need to have access to a NOAA Weather Radio.

Following the event, multiple survey teams were deployed to examine the severe weather episode. The teams were quickly organized and one team departed shortly after daybreak. Having a large pool of personnel trained for storm surveys and providing them with the tools needed, such as cameras and GPS equipment, is imperative for successful storm surveys.

Finally, this was obviously a very significant severe weather event. Nearly every staff member at the office participated, in some way, in the successful and timely services provided during or after the event. This included everything from issuing the forecasts and statements in preceding the event, issuing the warnings and coordinating with users during the event, participating in the damage surveys and creating the survey reports, covering shifts or providing resources during or after the event, or by participating in this event summary. This was truly a team effort.

Future Work

Examining the role that the wedge front and especially the coastal front played in the development, evolution, character, and degree of the severe weather. Identifying both boundaries and understanding their role in the future events is important.

More closely examining the relationship between the two mesocyclones as they interacted and produce a diagram of their position, strength, location, and evolution during the event.

Investigating the weakening of the thunderstorms and the greatly reduced amount of severe weather northeast of Rocky Mount in an area highlighted for its potential for severe weather.

Determining the percentage of tornado deaths that occur at night and the percentage of deadly nighttime tornado events across central North Carolina in the NWS Raleigh CWA using the same methodology as Ashley et al. (2008).

References

Ashley, W.S., A.J. Krmenec, and R. Schwantes, 2008: Vulnerability due to Nocturnal Tornadoes. Wea. Forecasting, 23, 795�807.

Ashley, W. S., 2007: Spatial and temporal analysis of tornado fatalities in the United States: 1880�2005. Wea. Forecasting, 22, 1214�1228.

Funk, T., 2002: Tornadogenesis in Supercells: The Three Main Ingredients http://www.crh.noaa.gov/lmk/soo/presentations/tornadogenesis.pdf

Locklear, C.B., 2008: A Severe Weather Climatology for the Raleigh, NC County Warning Area. NWS ER Technical Memorandum, 101.

Harris Interactive, cited 2007: Local television news is the place for weather forecasts for a plurality of Americans. Harris Poll No. 118. [Available online at http://www.harrisinteractive.com/harris_poll/index.asp?PID839.]

Monk, T. H., D. J. Buysse, L. R. Rose, J. A. Hall, and D. J. Kupfer, 2000: The sleep of healthy people�A diary study. Chronobiol. Int., 17, 49�60.

Simmons, K. M., and D. Sutter, 2005a: WSR-88D radar, tornado warnings, and tornado casualties. Wea. Forecasting, 20, 301�310.

Smith, T.M. and K. L. Elmore, 2004: The use of radial velocity derivatives to diagnose rotation and divergence. Preprints, 11th Conf. on Aviation, Range, and Aerospace, Hyannis, MA, Amer. Meteor. Soc., P5.6 - CD preprints.

Acknowledgements

Many of the images and graphics used in this review were provided by parties outside of the NWS Raleigh. The surface analysis graphics were obtained from the Hydrometeorological Prediction Center. GOES satellite data was obtained from National Environmental Satellite, Data, and Information Service. SPC meso-analysis graphics provided by the Storm Prediction Center. Base maps for the tornado tracks were provided by Google Maps and Google Earth - Google Earth map imagery used under license. NSSL's Rotational Track product provided by the WDSS-II (Warning Decision Support System - Integrated Information) group at NSSL. Local storm reports and warning polygons KMZ data provided by the National Climatic Data Center. Maps of warning polygons provided by the Iowa Environmental Mesonet. Historical tornado data provided by the National Climatic Data Center. Tornado statistics provided by the Storm Prediction Center.

Case study team -
Phillip Badgett
Jason Beaman
Terry Click
Darin Figurskey
Russ Henes
Brandon Locklear
Michael Moneypenny
Jeff Orrock
Scott Sharp
Barrett Smith
Michael Strickler
Jonathan Blaes

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

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