March 27, 2009 Tornado Event

Event Summary
National Weather Service, Raleigh NC

March 27, 2009 Tornado Event
Updated 2009/05/28

Collage of images related to this event

Event Headlines -
...The degree of severe weather across North Carolina was not anticipated. North Carolina was not included in any of the Day 1 severe weather outlooks included the outlook issued at 13 UTC by the Storm Prediction Center...
...An EF-1 tornado touched down near Hope Mills, NC while at least two weak EF-0 tornadoes touched down in Sampson and Johnston Counties...
...A surface front and resultant locus of low level shear, which may have aided in tornado formation, was located in very close proximity to the tornadic thunderstorms...
...While not a typical setup for tornadoes in the Carolinas given the limited instability, the presence of a strong trough and forcing aloft, the surface boundary, and adequate low and deep layer shear contributed to the development of low-topped supercells and tornadoes...
...Toward the end of the event, two mesocyclones interacted with each other and then appeared to merge over Johnston County...
...This was the third time that a home at the same location on Roslin Farm Road was damaged or destroyed by a tornado since the owner moved there in 1968...
...Impressive photographs and video were collected with the Hope Mills Tornado...

Event Overview -
An approaching short wave trough combined with weak instability, characterized by mixed layer and surface-based CAPE of around 250 to 500 J/kg, and deep layer shear of nearly 50 knots, led to the development of several low topped supercells during the afternoon of Friday, March 27, 2009. The presence of 0-3km SRH in excess of 300 m2/s2 and 0-1 km SRH around 125 m2/s2 in the vicinity of a surface boundary led to the development of thunderstorms with rotating updrafts and several tornadoes.

Event Details -
The upper air pattern during the afternoon of Friday, March 27, 2009 featured an intense, progressive closed low at 500 mb over northeastern New Mexico at 18 UTC that was associated with a significant winter storm in the Central Plains. A general west to southwesterly flow was in place at upper levels across the Southeast, with a shortwave trough present over southeast Tennessee and western Georgia at 18 UTC. This shortwave trough appeared to have been enhanced by an expansive MCS across the northeastern Gulf of Mexico. The shortwave trough was especially notable at 700 mb, with significant troughing of the height lines and drying behind the trough axis. The surface analysis provided by HPC indicated the primary surface front extended roughly from central South Carolina northeastward through the North Carolina Coastal Plain and the Eastern Piedmont to the Outer Banks.

Showers initially developed across far northeastern South Carolina just before 18 UTC. The approaching shortwave and the associated differential cyclonic vorticity advection provided larger scale forcing for ascent across the Carolinas. Theta-e advection associated with a low level jet centered around 850 mb (which could have been diabatically enhanced by the latent heating from the upstream MCS) also likely contributed to the convective development. The low level jet provided lift and a focus for convection near the surface boundary, while it also enhanced the low level shear. The thunderstorms developed in a region of increasing but weak instability just south of a developing boundary that bounded a nose of higher dew points across southeastern North Carolina. The surface-based CAPE values were on the order of 500 J/kg along and just south of the boundary. The 0-3 km mixed layer CAPE analysis showed CAPE values between 100 and 150 J/kg across the Sandhills and Southern Coastal Plain. There was a pocket of colder temperatures in the mid levels, which contributed to freezing levels around 9,000 to 10,000 feet over central North Carolina, with much warmer air aloft and higher freezing levels of 11,500 to 13,000 feet just upstream.

The 0-6 km bulk shear analysis at 21Z depicted values between 50-60 knots across the Sandhills and Coastal Plain of North Carolina. Such values are supportive of organized and persistent convection. The low level 0-1 km storm relative helicity (SRH) analysis placed values between 100 and 150 m²/s² across the Sandhills and Coastal Plain. Studies have shown that larger values of 0-1 km SRH, generally greater than 100 m²2/s², suggest an increased threat of tornadoes. The 0-3 km storm relative helicity data analyzed values around 200 m²/s² across the Sandhills and Coastal Plain. The 0-3 SRH is a measure of the potential for cyclonic updraft rotation in right-moving supercells, with larger values of 0-3 km SRH (greater than 100 m²/s²) suggestive of 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. On this particular day, the aforementioned low level shear values indicated the potential for supercells and tornadoes if storms developed, but that development was in question given the limited and poorly forecast amount of instability by the numerical weather prediction models.

The convection across far northeastern South Carolina just after 19 UTC began to intensify and evolve into low-topped supercells. Forecasters used AWIPS and other applications to view and interrogate level II radar data from KLTX (Wilmington, NC) and KCAE (Columbia, SC), which both revealed persistent but relatively weak low to mid level rotation. Extrapolation of these newly developed supercells, placed them just upstream of Cumberland County at around 500 PM. As the storms approached the NWS Raleigh forecast area, the updrafts continued to strengthen, and it was assumed the mesocyclones would also accordingly strengthen owing to the updraft induced stretching. The convection remained low topped with Echo Top values of around 25 kft and limited cloud to ground lightning.

SPC called to coordinate the prospects of a Tornado Watch, and it was jointly decided that a Tornado Watch would not be issued since 1) the threat was already ongoing and 2) the threat was expected to be limited in both time and space. Namely, the storms would soon cross into the surface based stable air north of the boundary, and the mid level warm advection would reduce lapse rates aloft and minimize buoyancy.

The mesocyclones maintained their intensity from the time they intensified just southwest of the NWS Raleigh CWA until about central Harnett County, at which time they gradually weakened and ultimately dissipated in the cooler, more stably-stratified air north of the surface boundary. Before doing so, however, the southeastern most mesocyclone that produced tornado damage in Sampson County wrapped northwestward toward the western Hope Mills tornadic circulation; and the circulations appeared to eventually merge over Johnston County (Java loop in which the user can stop, start, and animate the imagery). This process was similar to evolution and ultimate merger of the mesocyclones in the November 15, 2008 tornado outbreak, whereby the strongest tornado (EF-3 occurred at the time of the merger. Tornado Warnings were accordingly maintained and/or re-issued for the merging mesocyclones as far north as Johnston County, given that 1) the storms were still ingesting high theta-e, surface-based buoyant inflow air; 2) the storms were still tracking along or very near the storm relative helicity-rich surface front, and 3) the observational evidence of intense tornadogenesis after mesocylone merger during the November 15, 2008 outbreak. Indeed, there were two reports of tornadoes by trained Skywarn spotters as far north as central Johnston County, though no significant damage was noted in the vicinity of either of those reports.

One final interesting note, was that a low level mesocyclone persisted for around 30 to 60 minutes beyond the time of when its parent updraft had dissipated. The circulation was so impressive that a new Tornado Warning was at least considered, before ultimately deciding not to issue. It was thought that any circulation would not be strong enough to do damage and most definitely would not strengthen, owing to the lack of any robust updraft and stretching above.

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

Map of tornado tracks across NC on March 27, 2009

Map of tornado tracks across NC on March 27, 2009

The Hope Mills EF-1 Tornado

Video of the Hope Mills Tornado looking south across Interstate 95 - video courtesy of Brad Losh - click on the image to load video

The National Weather Service, in conjunction with Cumberland County Emergency Management, determined that an EF-1 tornado touched down just north of the Robeson County line, southeast of Hope Mills in the Roslin community. The tornado damage track was about 50 yards wide and stretched northeast for approximately 5 miles.

The EF-1 tornado initially touched down around 513 PM just north of the Robeson County line on Roslin Farm Road where a brick home lost more than eighty percent of its roof structure. A resident who was home at the time, took shelter in the bathroom just moments before the tornado struck. Interestingly enough, this was the third home to have been destroyed by a tornado at this same location since 1968 with all of the properties owned by the same resident. Several sheds and outbuilding in the area were also destroyed and a neighboring home suffered minor structural damage to the garage. The tornado then tracked northeast, over bare fields before reaching Braxton Road.

At Braxton Road, the tornado continued with EF-1 intensity winds that caused significant damage to a home which experienced around twenty percent roof loss. The house was a recently constructed well built two story home. The upstairs structure was seriously damaged and the house was condemned. Numerous sheds and fences were blown over in the area. One vehicle next door was moved nearly 50 feet from one side of the road to another. Just downwind from this home, a garage sustained significant damage. Several residents in the garage were informed of the Tornado Warning when a friend called them on a cell phone before the tornado hit. They then turned on television just moments before the tornado struck. Everyone in the garage took shelter under a billiards table. Two walls of the garage were blown out. In the same area a doublewide mobile home was blown about 5 feet off its foundation and lost nearly one hundred percent of its roof structure.

The tornado continued northeast crossing Chicken Foot Road and Corporation Drive along which several trees were snapped. The tornado crossed Interstate 95 where numerous trees were blown down and snapped near Tim Starling Road. It was just north of this intersection where a tractor trailer was overturned by the high winds. Just west of Interstate 95 near the intersection of Tim Starling Road and Research Drive, a large industrial building suffered significant roof damage. The wind of the tornado caused the roof the buckle enough for the Fire Marshall to order an evacuation of the building after the storm. Rocks on the roof of the building were blown into the parking lot shattering the windows of numerous vehicles. A large generator weighing a coupe thousand pounds was blown off a tractor trailer spilling around 40 gallons of diesel fuel. An unfinished house under construction on Tim Starling Drive was also significantly damaged. A storage warehouse in the same area sustained minor damage when one of the bay doors blew in.

The tornado continued tracking northeast along Research Road while weakening to EF-0 intensity as it approached Claude Lee Road. Numerous trees were blown down and sheds destroyed along Catherine Drive and Arlie Drive. Several homes in the area lost shingles and suffered minor damage to trim and siding. The tornado then lifted off the ground just as it approached the Fayetteville Regional Airport.

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

Time/Date: 513 PM to 520 PM EDT, Friday, March 27, 2009
Tornado:EF-1
Peak Wind: 86 - 90 mph
Path Length: 5.0 miles (from the Robeson County line northeast to near the Fayetteville Regional Airport)
Path Width: 50 yards
Injuries: none
Fatalities: none

Hope Mills Tornado Track -
Google Earth map imagery used under license

Hope Mills Tornado Damage Photos -
Photos courtesy of Cumberland County Emergency Management as well as Cheryl Jones and Steve Collins
(click on the image to enlarge)

Photo of tornado touchdown in a field looking west toward Roslin Farm Road - photo courtesy of Cheryl Jones and Steve Collins - Click to enlarge

Photo of tornado touchdown in a field looking northwest toward Braxton Road - photo courtesy of Cheryl Jones and Steve Collins - Click to enlarge

Hope Mills Tornado Video -
video courtesy of Brad Losh

The videos below were filmed on March 27th at approximately 510 PM EDT by Brad Losh looking south across Interstate 95. The videos show the large funnel that narrowed significantly at the ground. Strong rotation and lift can be seen around the funnel with the second video showing some debris being scattered in the air.

Note - the video is 15 seconds in length and approximately 4.5 MB in size.

Note - the video is 17 seconds in length and approximately 5.5 MB in size.

Hope Mills Tornado Radar Imagery -

The thunderstorm and low level circulation that produced the Hope Mills tornado intensified over Robeson County just before moving into southwestern Cumberland County. The radar image below is from the KRAX radar at 2103 UTC containing the 0.5 degree elevation angle of the storm relative velocity (left) and base reflectivity (right). The storm relative velocity imagery indicates an outbound velocity 24 knots and an inbound velocity of 41 knots producing a rotational shear value of 33 knots at a distance of 53 nm fro the radar and at an elevation of around 4,900 ft AGL. The VR shear values were computed to be 0.009/s. The 33 knots of rotational shear at 53 nm from the radar with a mesocyclone diameter of around 2 nm corresponds to a moderate to possibly strong mesocyclone on an interpolation of the 1.0 nm and 3.5 nm mesocyclone nomogram.

KRAX radar imagery from 2103 UTC of the 0.5 degree elevation angle of storm relative velocity and base reflectivity

KRAX radar imagery from 2103 UTC of the 0.5 degree elevation angle of storm relative velocity and base reflectivity

A Java loop in which the user can stop, start, and animate the imagery of the KRAX base reflectivity data from 2049 UTC through 2153 UTC March 27, 2009 is available here. Note - this loop includes 15 frames

Loop of the KRAX base reflectivity imagery from 2049 UTC through 2153 UTC March 27, 2009 - click to enlarge

A Java loop in which the user can stop, start, and animate the imagery of the KRAX storm relative velocity data from 2049 UTC through 2153 UTC March 27, 2009 is available here. Note - this loop includes 15 frames

Loop of the KRAX storm relative velocity imagery from 2049 UTC through 2153 UTC March 27, 2009 - click to enlarge

Hope Mills Tornado Warning Verification -

The Tornado Warning was issued at 505 PM EDT and valid through 530 PM EDT.
The tornado touched down at 513 PM and continued on the ground through 520 PM EDT.
The tornado lead time was 8 minutes.

NSSL's Rotational Track Product

Rotational track product from 18 UTC on March 27 through 06 UTC on March 28 - click on the image to enlarge

NOAA's National Severe Storms Laboratory (NSSL) has developed 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 18 UTC on March 27 through 06 UTC on March 28 combined with the tornado track and damage reports - click on the image to enlarge

The first image (click on it to enlarge), shown in the upper right includes the rotational track product from 1800 UTC on March 27 through 0600 UTC on March 28, 2009. Two long parallel corridors of rotation associated with the two low top supercells that moved over Cumberland, Sampson, and Johnston Counties are shown. Although subtle and not necessarily conclusive, there is some indication of greater rotational shear in southwestern Cumberland County and northwestern Sampson County. Regardless, the track and location of the shear observed by the radar is clear and this information was used during the damage survey the following morning.

The second image (click on it to enlarge), is zoomed in over the Hope Mills and Fayetteville area. In this picture, the rotational tracks data is shown with the tornado track (shown with red line) superimposed along with some damage reports. This image shows the impressive nature of this data set.

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 temperatures (red), dew points (blue) and shaded, and wind barbs from SPC at 21 UTC on Friday, March 27, 2009
The analysis shows one surface boundary which extends westward near the 60 degree isodrosotherm (dew point contour) from near Cape Hatteras to near Greenville to near Raleigh to near Charlotte. Temperatures south of the boundary reached the mid 60s to near 70 degrees and were supportive of surface based convection. South of this boundary, a smaller and more subtle boundary developed in the Southern Coastal Plain.

SPC Analysis at 21 UTC on Friday, March 27, 2009 - click to enlarge

500 MB heights, temperatures (red), dew points (green), and wind barbs (black) from SPC at 03Z on Saturday, May 10, 2008
The analysis shows an approaching short wave trough across far southwestern North Carolina and southwestern South Carolina with a pronounced wind shift to westerly from southwesterly. Note the large area of winds in excess of 50 kts across the Carolinas.

Analyzed mixed layer convective available potential energy (MLCAPE) (red) and mixed layer based convective inhibition (MLCIN) (blue lines - shaded) from SPC at 21 UTC on Friday, March 27, 2009
MLCAPE values were very limited with maximum values just exceeding 250 J/kg across the Sandhills and Southern Coastal Plain of North Carolina. There was little if any convective inhibition (CIN) across the same region. At the same time, the most unstable CAPE and the surface based CAPE were larger but only around 500 J/kg.
(Click on the image below to enlarge)

3 hour analysis of mixed layer convective available potential energy (MLCAPE) change from SPC at 21 UTC on Friday, March 27, 2009 Note the limited but still noteworthy decrease in stability across the Sandhills and Southern Coastal Plain of North Carolina.
(Click on the image below to enlarge)

0-6 km Bulk Shear (blue) and storm motion (brown) from SPC at 21 UTC on Friday, March 27, 2009
The 0-6 km bulk shear values range between 50-60 knots across the Sandhills and 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 21 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 21 UTC on Friday, March 27, 2009
Note that the 0-1 km SRH values range between 100 and 150 m²/s² across the Sandhills and 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 21 UTC on Friday, March 27, 2009
Note that the 0-3 Km SRH values range around 200 m²/s² across the Sandhills and 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) (fixed layer) and the mixed layer convective inhibition (MLCIN) from SPC at 21 UTC on Friday, March 27, 2009
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).

The modified STP formulation is as follows: STP = (sbCAPE/1500 J kg-1) * ((2000-sbLCL)/1500 m) * (SRH1/100 m2 s-2) * (6BWD/20 m s-1) * ((200+sbCIN)/150 J kg-1)

Analyzed values across central and eastern North Carolina were less then 0.5. The limiting factor which resulted in a reduced STP likely was the sbCAPE which was analyzed at the time to be around 500 J kg-1 or less while the mlLCL was around 500 m, the SRH1 was around 100 m2 s-2, and the sbCIN was near zero.
(Click on the image below to enlarge)

Analyzed Lifting Condensation Level (red, blue, and green) from SPC at 21 UTC on Friday, March 27, 2009
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 from between 500 to 750 meters.
(Click on the image below to enlarge)

NWS composite radar reflectivity imagery from 21 UTC on Friday, March 27, 2009.
The composite reflectivity imagery is from the approximate time in which the analysis imagery above is valid.

Composite Reflectivity Imagery from 21 UTC on Friday, March 27, 2009 - click to enlarge

KRAX Radar Loops

Overview of the entire event with images from every volume scan between from 2028 UTC through 2355 UTC on March 27, 2009.
Java loop of KRAX reflectivity imagery from 0403 UTC through 1128 UTC on March 27, 2009.
Note - this loop includes 100 frames

The KRAX reflectivity image below is from 2144 UTC or 544 PM EDT on Friday, March 27, 2009 as two low topped supercells were moving across Cumberland and Sampson Counties.

Regional Radar Loop

A Java loop of regional reflectivity imagery from 1801 UTC through 2351 UTC on March 27, 2009 is available here. Note - this loop includes 34 frames.

The regional reflectivity image below is from 2028 UTC on March 27, 2009. This was about 40 minutes before the first tornado touchdown in southwestern Cumberland County.

Regional reflectivity image - click to load loop

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

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Lessons Learned

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.

Forecasters used various situational awareness tools to stay abreast of the unfolding event. Information from law enforcement and emergency managers was supplemented by viewing local news media reports on a television monitor in the operations area.

Coordination between the NWS office in Wilmington, NC and the Raleigh, NC office was excellent. After receiving a report of a funnel cloud with a storm that was approaching the NWS Raleigh forecast area, a staff member at the Wilmington office called the Raleigh office and shared the report. A few moments later, around the time when the Raleigh office was creating the Tornado Warning for Cumberland County, the NWS office in Wilmington called Raleigh again and passed a long a report of possible damage with the same storm. The initial call from Wilmington raised an already elevated degree of situational awareness; the second call provided additional confidence to issue other warnings. The information from Wilmington was appreciated and indicative of the teamwork NWS offices use to fulfill the NWS mission to protect life and property.

Forecasters coordinated with SPC on at least two occasions, once initiated by NWS Raleigh at around 420 PM and the other by SPC a short time later. NWS Raleigh requested that one of the mesoanalysis sectors be moved from the Central U.S. to a location centered over southern North Carolina. A little later, SPC called to coordinate the prospects of a TOR Watch, and it was jointly decided that we would not issue one since 1) the threat was already ongoing and 2) the threat was expected to be limited in both time and space. Namely, the storms would soon (a couple of hours) cross into the surface based stable air north of the boundary, and mid level warm advection would reduce lapse rates aloft and minimize buoyancy.

The storm motion with the tornadic thunderstorms was around 220 at around 22 kts. A detailed meso-analysis indicated that a developing surface boundary extended northeastward to the west of but somewhat parallel to Interstate 95. As noted in Funk (2002), if supercell translates parallel to the boundary, then tornadogenesis is especially likely.

Interstate mile marker plots were very helpful when many incoming reports along I-95 mentioned mile markers. This helped locate where damage had occurred and also helped foresee where the tornado might cross the interstate again.

References

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

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. Tornado video courtesy of Brad Losh.

Case study team -
Phillip Badgett
Jeff Orrock
Barrett Smith
Michael Strickler
Jonathan Blaes

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