Tornadoes touch down near Fair Play and
Pendleton, South Carolina, on 8 April 2010.
Patrick D. Moore
NOAA/National Weather Service
A tornado touched down just north of Fair Play, South Carolina, on 8 April 2010, partially removing the roof of this home. Image by Tony Sturey, NWS.
Author's Note: The following report has not been subjected to the scientific peer review process.
During the afternoon and evening of Thursday, 8 April 2010, severe
thunderstorms developed ahead of a cold front over north Georgia and
moved across Upstate South Carolina and the western Piedmont of North
Carolina. The strongest of the storms were part of a short, quasi-
linear convective system (QLCS, or squall line). The QLCS produced
two tornadoes in Oconee County and Anderson County, South Carolina.
The first tornado occurred near Fair Play, South Carolina, at about
501 pm EDT (Eastern Daylight Time), or 2101 UTC (Universal Time
Coordinated). Part of a roof was blown off a manufactured home and
numerous trees were snapped or uprooted. The damage was rated at EF0
intensity on the Enhanced Fujita Scale. At about 526 pm EDT (2126 UTC),
another tornado touched down near Pendleton, South Carolina. The
second tornado was stronger than the first and produced a path of
damage about two miles long. Several barns and horse stables sustained
roof damage, several out-buildings were destroyed, and numerous trees
were snapped or uprooted. The damage from the second tornado was rated
at EF1 intensity. The same system produced damaging wind gusts over
northern Anderson County and west central Greenville County, South
Carolina, before it weakened. Other reports of damage were received
from Cleveland, Lincoln, Iredell, and Davie counties in North Carolina.
[Note: All times in this report from this point forward are expressed
in Universal Time Coordinated (UTC), which is EDT plus four hours. To
convert from UTC to EDT, subtract four hours from the UTC time.]
Click here to view a list of severe weather reports for 8 April 2010.
Figure 1. Preliminary reports of tornadoes, wind damage, and hail
received during the 24 hours ending at 1200 UTC on 8 April 2010. Click
on image to enlarge.
The Fair Play tornado appeared to be associated with a break in the
QLCS similar to what has been observed with tornadic QLCS events in
the western Carolinas, such as the Bessemer City, North Carolina,
tornado (January 2006) or the Liberty and Moore, South Carolina,
tornadoes (January 2007). The studies linked above dealt with QLCS
tornadoes in a high shear - low CAPE (HSLC) environment in the cool
season. The pre-storm environment on 8 April was characterized by
high shear and storm-relative helicity (SRH), low lifting condensation
level (LCL), and enough convective available potential energy (CAPE,
a measure of buoyancy of air parcels) to support the development of
supercell thunderstorms. What set the Fair Play storm apart was the
relatively high CAPE compared to other QLCS tornadoes associated
with line-breaks. Another interesting low reflectivity feature was
noted wrapping around the leading edge of the QLCS prior to the
development of the tornado.
2. Synoptic Features
For several days leading up to the event, forecasters at the National
Weather Service Greenville-Spartanburg (GSP) office expected conditions
to be favorable for at least isolated severe thunderstorms to the east
of the Appalachians on 8 April. The Day 2 Convective Outlook issued by
the Storm Prediction Center (SPC) at 1730 UTC on 7 April featured a
Slight Risk of severe thunderstorms over the Piedmont of the Carolinas.
The Slight Risk was expanded to cover even more of the western Carolinas
when the Day 1 Convective Outlook was issued at 0547 UTC on 8 April.
At 1200 UTC on 8 April, the 500 mb analysis featured a deep trough over
the middle of the country with a low center over Wisconsin (Fig. 2). A
deep southwest flow aloft was spread over the Southeast and Carolinas
between the upper ridge over the western Atlantic and the upper trough
axis that extended from the upper low south along the Mississippi River
to the northwest Gulf of Mexico. A short wave trough was located over
the Arklatex region with a belt of stronger winds in excess of 60 kt
ahead of the short wave from east Texas to the Ohio Valley. The eastward
movement of the short wave was expected to help spread the stronger
winds over the Carolinas later in the day.
Figure 2. Objective analysis of 500 mb geopotential height (black
contours), temperature (red dashed contours), and wind barbs at 1200 UTC
on 8 April 2010. Click on image to enlarge.
The stronger winds were also apparent on the 700 mb analysis (Fig. 3)
from central Mississippi to middle Tennessee and southwest Ohio. At
850 mb (Fig. 4), a cold front aloft was suggested from middle Tennessee
to southern Louisiana by the wind at Birmingham, Alabama, which was
backed relative to the southwest flow elsewhere across the Southeast.
This backing of the wind at 850 mb was expected to increase the potential
for rotating updrafts over the Piedmont as the cold front aloft
approached from the west later in the day.
Figure 3. Objective analysis of 700 mb geopotential height (black
contours), temperature (red and blue dashed contours), dewpoint (green
contours), and wind barbs at 1200 UTC on 8 April 2010. Click on image
Figure 4. Objective analysis of 850 mb geopotential height (black
contours), temperature (red and blue dashed contours), dewpoint (green
contours), and wind barbs at 1200 UTC on 28 March 2010. Click on image
At the surface, a cold front stretched from middle Tennessee to southeast
Louisiana (Fig. 5). The convective mode was expected to be linear later
in the day because of the mainly unidirectional winds aloft and the deep
layer shear vector nearly parallel to the cold front, as outlined in the
Day 1 Convective Outlook issued by the SPC at 1257 UTC. A broken line of
convection across eastern Tennessee and northwest Georgia (Fig. 6), with
a trailing region of stratiform rain ahead of the cold front, was expected
to gradually weaken and dissipate during the morning hours. In fact, the
convection weakened through the early afternoon as expected, and left
considerable cloudiness across the western Carolinas that slowed the
destabilization of the air mass east of the mountains. However, severe
thunderstorms, remained a possibility as the low level jet moved across
the Carolinas during the time of peak heating. The Slight Risk was
unchanged on the Day 1 Convective Outlook updated at 1750 UTC.
Figure 5. HPC Surface fronts and pressure analysis at 1200 UTC on
8 April 2010. Click on image to enlarge.
Figure 6. Composite reflectivity mosaic centered on GSP at 1300 UTC on
8 April 2010. Click on image to enlarge.
At 1800 UTC, the cold front reached from east Tennessee and across the
northwest tip of Georgia to eastern Alabama (Fig. 7). Water vapor
satellite imagery showed the leading edge of dry air at mid levels moving
across Alabama (Fig. 8), indicative of stronger winds and subsidence
behind the cold front. Between 1800 UTC and 1900 UTC, a new line of
convection developed near Atlanta, Georgia, which continued to strengthen
as it moved across north Georgia (Fig. 9).
Figure 7. HPC surface fronts and pressure analysis central east sector
at 1800 UTC on 8 April 2010. Click on image to enlarge.
Figure 8. GOES-12 water vapor satellite imagery at 1745 UTC on 8 April
2010. Brightness temperatures are given by the color scale on the
bottom of the image, with red and black corresponding to drier air at
mid levels. Click on image to enlarge.
Figure 9. As in Fig. 6, except at 1957 UTC on 8 April 2010. Click on
image to enlarge.
Click here to view a 17 frame Java loop of GOES-12 water vapor channel
satellite imagery from 1145 UTC on 8 April to 0345 UTC on 9 April.
Click here to view a 10 frame Java loop of a regional reflectivity mosaic
from 1158 UTC to 2100 UTC on 8 April.
3. Pre-Storm Environment
The environment across northeast Georgia and western South Carolina
ahead of the convection moving across north Georgia at 2000 UTC was
characterized by high shear and a modest amount of buoyancy. The
shear in the surface to 1 km layer was at least 40 kt across most of
Upstate South Carolina (Fig. 10a). Shear values of 40 kt or greater
in the layer from the surface to 2.5 km are thought to be sufficient
to the production of low-level mesovortices in a QLCS as suggested by
the modeling studies of Weisman and Trapp (2003). The lowest 100 mb
mean lifting condensation level (LCL) was on the order of 500 to
750 m (Fig. 10b). The combination of a relatively high 0-1 km shear
of 40 kt and relatively low LCL of 750 m suggested a relatively high
probability that a tornado would occur (Brooks and Craven, 2002).
The effective storm relative helicity (SRH) was on the order of
200–300 m2 s-2 (Fig. 10c), which was indicative of a high potential for
tornadic supercells. Values of CAPE for the most unstable air parcels
were on the order of 500–1000 J kg-1 (Fig. 10d). Although the CAPE was
modest, the high values of effective SRH and effective bulk wind shear
(Fig. 10e) yielded a supercell composite parameter value between 2 and
4 (Fig. 10f), which was indicative of a high potential for right-moving
Figure 10. SPC objective mesoanalysis at 2000 UTC on 8 April 2010
showing (a) surface - 1 km shear (kt; blue contours) and shear vector
(kt; barbs), (b) 100 mb mean parcel LCL height (m AGL; green and brown
contours, color fill above 2000 m), (c) effective SRH (m2s-2; blue
contours), effective inflow base (m AGL; color fill), and storm motion
(kt; barbs), (d) most unstable CAPE (J kg-1; brown contours) and lifted
parcel level (m AGL, black contours and color fill), (e) effective bulk
shear (kt; blue contours and color fill), and (f) supercell composite
parameter for the effective layer (blue contours) and Bunkers storm
motion (kt; barbs). The area of interest, Oconee County (O), Pickens
County (P), and Anderson County (A), South Carolina, is shaded light
blue. Click on each image to enlarge.
The less-than-optimal thermodynamic environment was thought to be a
limiting factor, but the favorable shear would support isolated
tornadoes and wind damage, as stated by the SPC in a mesoscale
discussion issued at 2000 UTC. The continued development of a line
of thunderstorms toward more favorable buoyancy motivated the SPC to
issue a Tornado Watch (#0066) for part of northeast Georgia and all
of Upstate South Carolina at 2031 UTC.
4. Radar Observations
Between 2000 UTC and 2030 UTC, the convection moving across north
Georgia had consolidated into a short QLCS from western Oconee County,
South Carolina, to Barrow County, Georgia. A bowing segment of the
line was located over Franklin County, Georgia. A comparison of 0.5
degree scans from the KGSP radar between 1957 UTC and 2031 UTC showed
evidence of a rear inflow jet impinging upon the upshear side of the
QLCS immediately behind the bowing segment (Fig. 11). A relative
desiccation of reflectivity was noted behind the bowing segment, which
could have been the result of drier air descending from mid-levels
behind the QLCS. The base velocity data showed an area of stronger
inbound echoes immediately behind the bow in western Franklin County.
Figure 11. KGSP radar 0.5 degree (a) base reflectivity and (b) base
velocity at 1958 UTC, and (c) base reflectivity and (d) base velocity
at 2031 UTC. The reflectivity color table is shown on the left bar and
the velocity color table is shown on the right color bar. Note the hole
of no reflectivity over Homer in (c). The diamond shape in (c) and
(d) denotes the location of a radar-detected hail core. Note the region
of higher velocity in the darker green color to the west of the diamond
in (d) corresponding to the concave reflectivity gradient in (c). Click
on image to enlarge.
An interesting feature developed on the southeast flank of the bowing
segment of the QLCS between 2023 UTC and 2036 UTC (Fig. 12). Within a
larger area of stratiform-like precipitation preceding the QLCS, a patch
of low reflectivity appeared over southern Franklin County by 2027 UTC.
There was some evidence of the low reflectivity area first on the
1.8 degree scan at 2019 UTC, which suggested downward development of
this feature. The low reflectivity area elongated north to south and
moved into the western part of Hart County, Georgia, by 2036 UTC, and
then wrapped around the eastern flank of the QLCS near Fair Play by
2044 UTC. Meanwhile, an inflection point developed along the QLCS
between 2031 UTC and 2044 UTC, and was located between Lavonia and Lake
Hartwell at 2044 UTC.
Figure 12. KGSP 0.5 degree base reflectivity at (a) 2023 UTC,
(b) 2027 UTC, (c) 2031 UTC, (d) 2036 UTC, (e) 2040 UTC, and (f) 2044 UTC.
The reflectivity values are given by the color table in the upper left
corner of each image. The yellow arrow in (c) shows the location of the
weak echo channel and the length of the arrow is 10 miles. Click on
image to enlarge.
Between 2040 UTC and 2052 UTC, the bowing segment of the QLCS surged
forward at approximately 60 kt from northeast Franklin County, across
extreme southern Oconee County, to Townville, South Carolina (Fig. 13
and 14). A break in the line occurred on both the 1.3 degree and
1.8 degree scans by 2052 UTC, which corresponded to a range of elevation
from 7,000 ft to 13,000 ft AGL in the storm. No break was discernable
on the lowest two elevation cuts, although a forward bulge was evident
to the northeast of Fair Play.
Figure 13. KGSP base reflectivity at 2040 UTC on the (a) 0.5 degree,
(b) 0.9 degree, (c) 1.3 degree, and (d) 1.8 degree scans. The reflectivity
color table is given by the table in the upper left corner of each image.
Click on image to enlarge.
Figure 14. As in Fig. 13, except for 2052 UTC. Click on image to enlarge.
Although broad rotation was associated with the bowing segment of the
QLCS, maximum rotational velocity and shear were considered insignificant
on the lowest three elevation scans from the KGSP radar through 2048 UTC
(Fig. 15), as both measures of mesocyclone strength remained in the "weak"
or "minimal" categories. A small jump was noted in rotational velocity
at all three levels at 2052 UTC, but this only brought the rotation into
the "minimal mesocyclone" range, where it remained during the 2057 UTC
volume scan. The shear remained minimal but with an increasing trend
through 2057 UTC as the distance between regions of inbound and outbound
storm relative motion decreased. On the 2101 UTC scan, the maximum
rotational velocity showed another small increase, but the maximum
rotational shear almost doubled to 0.0201 s-1, which was at the threshold
between the "tornado possible" and the "tornado probable" regions of the
Rotational Shear Nomogram. The tornado touched down 0.5 miles north-
northwest of Fair Play at this time. Prior to the tornado, there was no
conclusive evidence to suggest a mesocyclone developing downward from
mid-levels. The rotational shear dropped back to pre-tornado values at
2105 UTC but rotational velocity on the 0.5 degree scan maximized at 31 kt,
which placed the rotation at the threshold of the minimal and moderate
categories on the mesocyclone nomogram. By this time, the tornado had
Figure 15. Maximum rotational velocity (a) and rotational shear (b) observed
on the lowest three elevation scans from the KGSP radar from 2031 UTC to
2151 UTC. The velocity and shear data are organized according to the Fair
Play storm (solid lines on the left) or the Pendleton storm (dashed lines
on the right). The pink colored vertical bars represent the time of the
Fair Play tornado (2101 UTC) and the Pendleton tornado (2126 UTC to
2129 UTC). Click on image to enlarge.
A large coherent area of outbound storm relative motion was present by
2052 UTC over southwest Oconee County, but the inbound portion of the
circulation was not as well organized (Fig. 16). Most of the inbound
targets were along and ahead of the southeast flank of the QLCS with a
smaller area east of Lavonia, Georgia. By 2057 UTC, the circulation
had the appearance of tightening because of a patch of inbound targets
drawing closer to the outbound region. At 2101 UTC, when the tornado
was on the ground, a very small inbound area (two range gates) was
adjacent to the larger outbound portion of the rotational signature.
The maximum outbound storm relative motion increased 66% between 2057 UTC
and 2105 UTC (from 26 kt to 43 kt) over southern Oconee County on the
0.5 degree scan. Reflectivity images gave only subtle clues prior to
the tornado, mainly limited to a weak echo channel oriented along
Interstate 85 in southern Oconee County punching into the rear flank of
the QLCS (Fig. 17). The break in the QLCS was not apparent on the
0.5 degree elevation scan until 2105 UTC, by which time the tornado had
Figure 16. KGSP storm relative motion on the 0.5 degree scan at
(a) 2052 UTC, (b) 2057 UTC, (c) 2101 UTC, and (d) 2105 UTC. The color
table in the upper left corner of each image shows the magnitude of the
component of motion toward or away from the radar along the radial. In
general, green shades represent motion toward the radar and red shades
show motion away from the radar. The dashed purple line is the border
between South Carolina and Georgia. The blue line is Interstate 85.
County boundaries are shown in grey. The location labeled “Home”
denotes the approximate location where the Fair Play tornado touched
down at 2105 UTC. Click on image to enlarge.
Figure 17. KGSP base reflectivity on the 0.5 degree scan at (a) 2052 UTC,
(b) 2057 UTC, (c) 2101 UTC, and (d) 2105 UTC. The color table in the
upper left corner of each image gives the reflectivity value. The dashed
purple line is the border between South Carolina and Georgia. The blue
line is Interstate 85. County boundaries are shown in grey. The location
marked “Home” is the approximate location where the Fair Play tornado
touched down at 2101 UTC. Click on image to enlarge.
Reflectivity data gave no meaningful clues as to the development of the
second tornado. The apparent break in the QLCS filled in by 2114 UTC.
Broad rotation continued across the QLCS in the vicinity of Townville,
South Carolina, at 2109 UTC and 2113 UTC (Fig. 18). The rotation became
better organized between 2113 UTC and 2122 UTC as the couplet moved
across the area between Pendleton and Sandy Springs. Maximum rotational
velocity increased steadily and the distance between maximum inbound and
outbound decreased (Fig. 15). Rotational shear peaked at 0.037 s-1 (in
the "tornado likely" category) on the 0.9 degree scan at 2126 UTC as the
gate-to-gate difference between inbound and outbound storm relative motion
peaked. The Pendleton tornado touched down at this time. The tornado
remained on the ground through approximately 2129 UTC, after which
rotational velocity and shear diminished.
Figure 18. KGSP storm relative motion on the 0.5 degree scan at
(a) 2109 UTC, (b) 2113 UTC, (c) 2118 UTC, (d) 2122 UTC, (e) 2126 UTC,
and (f) 2130 UTC. The location marked "Home" is the location where the
Pendleton tornado touched down at approximately 2126 UTC. The polygon
boundary for Tornado Warning #0015 is shown as the broken light blue line.
County boundaries are shown in light gray. Click on image to enlarge.
Click here to view a 25 frame Java loop of KGSP 0.5 degree base reflectivity
from 2002 UTC to 2143 UTC on 8 April.
Click here to view a 25 frame Java loop of KGSP 0.5 degree storm relative
motion from 2002 UTC to 2143 UTC on 8 April.
Clues that a tornado was imminent were subtle up until the radar volume
scan during which the Fair Play tornado touched down. Evidence suggested
the Fair Play tornado was preceded by a rear inflow jet which caused the
QLCS to bow forward and a weak echo channel that wrapped around an
inflection point on the convective line. The tornado was accompanied by
a break in the QLCS whereby the tornado formed at the southern end of the
trailing line segment. Similar radar signatures have been associated with
QLCS tornadoes in HSLC environments (Lee and Jones 1998; McAvoy et al. 2000;
Lane and Moore 2006). However, the break in the line was not evident on
the 0.5 degree elevation scan until the volume scan after the tornado had
already lifted. The maximum rotational shear did not reach the threshold
for tornado warning issuance (greater than 0.020 s-1) until the tornado was
already on the ground.
The environment on 8 April contained more CAPE and more SRH than what was
present in the "broken-S" QLCS tornado events documented in the studies
above. In fact, the environment on 8 April appeared more supportive of a
QLCS with embedded supercellular elements and perhaps discrete right-moving
supercells. One of the few tools the warning forecaster has for the issuance
of a successful tornado warning in a "broken-S" situation is an awareness
of the HSLC environment that usually accompanies such events. Situational
awareness among the warning team of the possibility of a "broken-S" signature
was relatively low because the forecast area was not in the typical HSLC
environment. A QLCS with embedded bows and supercells was the expected mode
An interesting reflectivity feature developed on the southeast flank of
the QLCS approximately 35 minutes before the Fair Play tornado. A patch
of lower reflectivity appeared to descend and elongate in the direction
of the wind in the stratiform rain area ahead of the QLCS. The lower
reflectivity patch proceeded to wrap around the eastern flank of the QLCS
about 10 – 15 minutes before tornadogenesis. This feature had not been
noticed in similar QLCS tornado events in the past. The QLCS on 8 April
had characteristics similar to the "leading stratiform" mode of mesoscale
convective system outlined by Parker and Johnson (2000). It would be
interesting to re-investigate previous "broken-S" events in light of
Parker and Johnson (2000) to determine the organizational mode of the
QLCS and see if any were of the leading stratiform variety and if a
similar feature was present.
Pictures of the damage from the Pendleton Tornado
Pictures of the damage observed from the Pendleton tornado on 8 April 2010.
Click on image to enlarge.
Brooks, H. E., and J. P. Craven, 2002: A database of proximity soundings
for significant severe weather. Preprints, 21st Conf. on Severe
Local Storms, San Antonio, TX, Amer. Meteor. Soc.
Lane, J. D., and P. D. Moore, 2006: Observations of a non-supercell
tornadic thunderstorm from a Terminal Doppler Weather Radar.
Preprints, 23rd Conf. on Severe Local Storms, St. Louis, MO, Amer.
Lee, L. G., and W. A. Jones, 1998: Characteristics of WSR-88D velocity
and reflectivity patterns associated with a cold season non-supercell
tornado in upstate South Carolina. Preprints, 19th Conf. on Severe
Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 151-154.
McAvoy, B. P., W. A. Jones, and P. D. Moore, 2000: Investigation of an
unusual storm structure associated with weak to occasionally strong
tornadoes over the Eastern United States. Preprints, 20th Conf. on
Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 182-185.
Parker, M. D, and R. H. Johnson, 2000: Organizational modes of midlatitude
mesoscale convective systems. Mon. Wea. Rev., 128, 3413-3436.
Weisman, M. L., and R. J. Trapp, 2003: Low-level mesovortices with squall
lines and bow echoes. Part I: Overview and dependence on environmental
shear. Mon. Wea. Rev., 131, 2779-2803.
The damage survey for the Fair Play and Pendleton tornadoes was
conducted by Tony Sturey and Justin Lane (NWS). The local storm
report map and upper air analyses were obtained from the Storm
Prediction Center. The mesoscale objective analysis was prepared
by the SPC and obtained from the archive at the NWS office in Omaha,
Nebraska. The surface fronts and pressure analyses were obtained
from the Hydrometeorological Prediction Center. The satellite
imagery and radar mosaic imagery was obtained from the University
Corporation for Atmospheric Research. Some of the radar graphics
were created using the GRLevel2 Analyst software. The plots of
maximum rotational velocity and shear were created using Microsoft
Excel. The tornado track map was made using Delorme Street Atlas
USA 2009 Plus.