6 AUGUST 1993 SOUTHEAST VIRGINIA TORNADO
THE PETERSBURG, VIRGINIA F4 TORNADO
Report written by
Barbara McNaught, Warning Coordination Meteorologist
at the NWS Baltimore-Washington Forecast Office
Laura Cook, Meteorologist-in-Charge
at the NWS Norfolk Weather Office
and Central Wills, Officer-in-Charge
at the NWS Richmond Weather Office
Tornadoes are not considered a common event in Virginia and many of the
Commonwealth's people will tell you that they do not even consider
tornadoes a threat. August 6, 1993 broke that myth and shocked many with
the reality of destruction that tornadoes bring. Prior to 1993, Virginia
averaged six tornadoes a year. Records kept since 1950 showed 263 total
tornadoes reported in the state, 21 fatalities, and 192 injuries. There
have been 56 fatalities since 1916. The most active year for tornadoes was
1975 with 22 and the most active day was October 13, 1983 with 10
These statistics should help place in context the August 6, 1993
outbreak. Many records were broken. Eighteen tornadoes occurred on that
day smashing the old record of ten. This brought the total for the year to
25 breaking the old record of 22 only eight months into the year. The
Petersburg Tornado was rated an F-4 on the Fujita Damage Scale (see table
1) with estimated winds peaking near 210 mph. This is the strongest
recorded tornado in Virginia since 1950. It was the costliest tornado with
an estimated 47 million dollars in damages. The total estimated damage
from the outbreak was 52.5 million dollars. Twenty-one Virginia
jurisdictions were affected by tornado impacts.
This was not the deadliest tornado outbreak for
Virginia. That occurred May 2, 1929 when five tornadoes killed 21 people
and injured 70. In 1929, it was a relatively unpopulated state and there
may have been more tornadoes that day that went unreported. By comparison,
the August 6 tornadoes killed four and injured 259 people. The tornado
that struck Petersburg injured as many people as all the tornadoes
combined for the past 40 years in Virginia. While not the deadliest, it was
the worst tornado as far as total citizens in the commonwealth affected.
We can thank the rapid response of emergency services and medical
personnel for saving lives and minimizing the potential death toll from
After the Petersburg tornado, some people talked about how unusual it
was for a tornado to strike that area of Virginia. While it was an unusual
event, it was not a first. Petersburg was struck by an F-2 tornado on June
21, 1970 and an F-3 tornado on May 8, 1984. While no deaths or injuries
occurred, there was significant damage. Nearby counties such as
Chesterfield, Dinwiddie, Prince George, and Charles City have recorded
nine, four, four, and five tornadoes respectively since 1950. Chesterfield
has been one of the hotter tornado spots in Virginia's history.
Scale (F-scale) of Tornado Winds and Damage
||Examples of Damage
||# in Va
|Light damage. Tree branches
snapped; rotten trees down; TV antennas and signs damaged.
||Moderate damage. Roofs peeled off;
windows broken; trees snapped; trailers moved or overturned.
||Considerable damage. Roofs torn
off; weak structures and trailers demolished; trees uprooted; cars
blown off road.
||Severe damage. Roofs and some walls
torn off well constructed houses; some rural buildings demolished;
cars lifted and tumbled.
||Devastating damage. Houses leveled
leaving piles of debris; cars thrown some distance.
||Incredible damage. Well-built
houses lifted clear off foundation and carried a considerable
distance and disintegrated.
Tornado 1 Lunenburg-Nottoway-Dinwiddie-Chesterfield
First touch down of the day occurred near the town
of Kenbridge in Lunenburg County at 12:43 pm. Roofs were blown off a
briquet plant and a furniture company. The tornado moved northeast into
Nottoway County. Estimated damage to Luneburg County was 300,000 dollars.
The tornado began as an F-0 on the Fujita damage scale with a path width
In Nottoway County the tornado strengthened to an
F-1 were it leveled a barn, trees and some outbuildings on Route 46 near
the west edge of Fort Pickett Military Reservation. A house along Route 46
also sustained some damage. Total damages in Nottoway County were
estimated at 100,000 dollars. The tornado width was 100-150 yards.
crossed into Dinwiddie County on the Fort Pickett Military Reservation
where it did minimal damage. The tornado crossed route 643 near the
northeast corner of Fort Pickett and continued northeast across rural land
to the town of Ford. By this point it had strengthened to an F-2. It
struck a well-constructed house on route 622 in the town of Ford at 1:12
pm. The second level of the house was sheared off along with some of the
wall. There were also windows gone on the first level. A 97 year old widow
road out the storm in the first floor hallway closet. Near the house, a
wooden shed, telephone poles, and large trees were leveled. The tornado
tracked northeast to near the Chesterfield County line. It lifted near
route 611 and 623. Average width was 150-175 yards. Total damage was
About 5 miles to the northeast in Chesterfield
County, the tornado again touched down with damage along Route 628, 634
and 692 for about 3.5 miles. The damage is rated F-0.
Total path length through the 4 counties was about 38 miles. Total damages
are estimated at 720,500 dollars. Total life time of the tornado on the
ground was about 40 minutes.
Tornado 2 Petersburg-Colonial
devastating tornado of the day touched down in the independent city of
Petersburg at approximately 1:30 pm. This tornado rapidly grew in size and
strength as it moved two miles northeast into the commercial historic
district of Petersburg. Here, damage showed a path width of 300 yards.
Much of this damage was of an F-2 magnitude, however, within this path
were smaller paths (about 30 yards wide) of more concentrated F-4 damage
(winds estimated near 210 mph). Because of this pattern, the tornado has
been designated an F-4 multi-vortex tornado. The vortex of a large tornado
can sometimes break down into smaller tornadoes which rotate around a
central core. This is called a multi-vortex tornado.
Amazingly, no one was killed in Petersburg. Old
Towne Petersburg had withstood Union troop barrages in 1864-65 during the
Civil War. Most of the buildings date back to the mid 1800s. A fire in
1815 destroyed the original Old Towne which was established in the 17th
century. The train station that was demolished was the oldest standing
train station in Virginia. Fifty-eight buildings were badly damaged or
The end unit of a row of three-story brick
buildings was completely demolished so that all that remained was a
portion of the first level back and side walls. This was a
well-constructed building with the brick walls at least three bricks
thick. In another row of two- and three-story attached buildings, a middle
unit was demolished. This was also a three-story brick building. About
three feet of the first level front wall remained and most of the first
level back wall remained. The rest was gone along with the attached
sidewalls of the adjacent units second and third levels. In the first
floor was a restaurant. Thirty people were in this building, yet no one
About 100 feet or so to the right of the
restaurant was the historic train station which was completely collapsed.
This was a one or two story brick structure that had a large spanning roof
making it more susceptible than the other units mentioned to being
destroyed. A couple units to the left of the restaurant was a unit that
had a solid brick wall with no windows. The wall was four bricks thick. A
large hole about 2 to 3 feet in diameter had been punched through the
wall. This was likely caused by an airborne missile generated by the
tornado, perhaps a beam from the buildings roof. Behind this building was
another row of buildings. A collapsed wall was observed to have been made
of cinder blocks with steel reinforcement rods and a layer of bricks on
F-4 tornado winds were determined based on the
construction, design and damage to the above mentioned buildings. Also of
interest was a caboose located behind a building near the train station.
The caboose had been anchored into ground and setting on a short piece on
rail. The tornado moved the caboose about 20 feet off the track ripping
the anchors from the ground. The caboose was moved in an opposite
direction to the path of the tornado.
From Old Towne, the tornado moved across to the
historic black neighborhood of Pocahontas Island at about 1:35 pm. Here it
destroyed or heavily damaged 47 of the 57 homes on the island. Most of
these homes were wood-framed houses. A 200 year old church was totally
destroyed, however, a bible, open on a podium, was untouched. Damage was
rated at an F-3 with a path width of 250 yards. Total damage to Petersburg
and Pocahontas Island was estimated at 15 million dollars. Forty people
were injured and over 100 buildings heavily damaged or destroyed, but
there were no deaths.
From Pocahontas Island, the tornado crossed the
river entering Colonial Heights and crossing Interstate 95 to the
Southpark shopping area. Amazingly, no vehicles where struck on this
normally very busy highway. Here, it went on to damage several large
stores including a K-Mart, a waterbed store, a strip mall (Southgate
Square) and then the Wal-Mart. Windows were blown out, some walls and
roofs collapsed at the stores. Some remaining walls were splattered and
pitted with debris. The tornado had narrowed to about 200 yards wide by
this point (as described by eyewitnesses) and was weakening, but it still
retained its multi-vortex characteristics when it struck the Wal-Mart.
The tornado was as wide as the Wal-Mart was long.
It moved across the length of the store. A small vortex within the tornado
struck the front of the store to the right of the main entrance area
slicing a 20 yard wide path through the cinder-block wall and store roof.
(This was from a vector direction of 230 degrees converging into the main
path of the tornado). The vortex gives the storm a rating at the lower end
of an F-3 with winds up to 175 mph. Damage outside the small vortex was
Three people were killed near the store front and
another 198 injured. The deaths were to three women, 40, 48 and 56 years
of age. In the parking lot between the Wal-Mart and Southgate Square, 500
cars were removed, all with windows blown out and many completely totaled
having been tossed about and flipped over. Of the 185 people brought to
area hospitals from Petersburg and Colonial Heights, only 23 had to be
admitted. This is considered a typical percentage for disasters. Total
damage in Colonial Heights was estimated at 29.5 million dollars.
Form the Wal-Mart, the tornado crossed the
Appomattox River again, this time entering Prince George County. About a
mile from the Wal-Mart at about 1:40 pm, it struck Tarmac Virginia, Inc.,
a sand and gravel pit company located on Puddledock Road. The second floor
of the cinder block building collapsed. Several employees had sought cover
there. One 28 year old man was crushed and killed between the cinder
blocks and a large electrical panel that fell. Several cars and trucks
were overturned. Large conveyor belts were twisted and overturned. One
employee spotted the tornado and radioed a warning to others which likely
saved some lives. Three employees evacuated a small shed just before it
was totally destroyed.
The tornado path width was 125 yards. It was a
strong F-2 with winds estimated near 150 mph. Damage at the Tarmac site
was estimated at three-quarters of a million dollars. The remaining damage
across Prince George County was primarily to trees.
The tornado crossed Interstate 295 damaging a tall
brick barrier wall and headed for the independent city of Hopewell. Here
it sliced through the northern section. Hardest hit was the Riverside Park
Apartment Complex were it took off several roofs. The tornado caused minor
damage to an additional 49 homes, major damage to 13 homes and destroyed
two. It struck Hopewell around 1:45 pm. The tornado was rated an F-1 with
a width of 75 to 100 yards. Damages were estimated at 2.2 million dollars.
Eight people were injured.
The tornado weakened to an F-0 as it crossed Route
10 near the bridge and moved out over the confluence of the Appomattox and
James Rivers. It dissipated before entering Charles City County. Total
path length through three independent cities and one county was about 12
miles. Total damages were estimated at 47.5 million dollars. Total life
time of the tornado on the ground was 15 to 20 minutes.
Tornado 3 Chesterfield-Henrico-New Kent
Within close proximity time- and distance-wise to
the Petersburg tornado, another tornado touched down to the north in
Chesterfield County. This tornado formed from the same storm that produced
the Dinwiddie County tornado.
The tornado touched down and crossed Route 10
moving northeast into the Rivers Bend subdivision at about 1:40 pm. It
produced widespread tree damage and only minor roof and window damage to
the new well-constructed homes in the neighborhood. The tornado was rated
an F-1 with a width of about 200 yards (most concentrated area of damage).
The damage path to trees was actually about a half mile wide and it is
estimated that the entire meso-cyclone (low pressure center of a
thunderstorm complex) was on the ground. Strong inflow into the storm
caused minor tree damage as wide as a mile across.
The tornado moved from Rivers Bend to strike the
Virina-Enon Bridge on Interstate-295. The tornado sucked up water from the
James River and was described as a rotating wall of water striking the
bridge. It knocked over two tractor-trailer trucks on the bridge and
flipped over two smaller trucks. Another tractor-trailer truck then
collided with the first two. Five people were injured.
The tornado weakened to an F-0 as it moved
northeast across Henrico County causing tree damage. The storm's path
width had narrowed to 75 to 100 yards. It finally dissipated in New Kent
County in the vicinity of Route 60 and 640. Total Path length was about 14
miles. No damage estimates were obtained for this tornado.
Tornado 4 - Charles City-New Kent
About 8 miles northeast of the Petersburg tornado
track, another tornado touched down. This was likely produced by the same
thunderstorm. Credible sources indicated material from the Wal-Mart could
be found in the southwest portion of Charles City County (some 15 miles
from the store). In Charles City County, along Route 650 and 609, tree
damage begins. The time was estimated between 2:00 and 2:05 pm.
The tornado broadsided a mobile home rolling it on
its side and destroying it. The home had been anchored at all four
corners. The anchors were set three feet into the ground. The tornado
continued across Cool Hill Road. Another anchored mobile home was rolled
three times and completely demolished. The remaining damage to Charles
City County was trees. Estimated damages were 115,000 dollars.
The tornado moved into New Kent County, crossed
over highway 60 and dissipated. Damage to New Kent was to trees. Path
width was 50 yards. The total path length was 6.5 miles. It was rated an
Tornado 5 - New Kent
Another tornado touched down in New Kent County.
It was slightly to the right of the previous tornado and was, again,
likely produced by the same storm. Damage began south of Interstate 64 and
just west of Route 628. This was a wooded area. The tornado tracked
north-northeast crossing I-64 at mile marker 217. The tornado track turned
a little more to the northeast and then back to the north-northeast as it
dissipated in the vicinity of Route 623 a little over a mile east of the
New Kent County Court House. The total tornado path length was 4.75 miles.
No dollar damage estimate.
Almost all of the damage in the county was to
downed trees. Homes in the area did not sustain any wind damage. The path
was largely inaccessible by foot and so most of the damage assessment was
done by aerial survey by the county emergency services director. The
initial touchdown width was 30 yards. At I-64 the tornado had widened to
about 150 yards and F-1 intensity. The damage pattern was complicated by
additional areas where tree damage widen to nearly half a mile. At first
glance, it seemed this could be described by the storm also producing a
micro burst. However, no other micro burst damage was found to have
occurred from thunderstorms that day. Upon viewing pictures of the tree
damage more closely, trees were not lain in a straight line pattern, but
in a broader cyclonic pattern. Therefore, it is theorized that again the
whole meso cyclone (rotating core of the thunderstorm complex) briefly
Tornado 6 - Southampton
At about 2:20
pm, a cooperative observer sighted a tornado about 4 miles west of
Courtland. At that time it was seen throwing trees into his barn. Trees
were uprooted and a shed was destroyed. The tornado moved over open fields
with little else in its path to damage. The tornado was a F-0 to a low F-1
with a path length of about a mile. Estimated path width is 75 yards.
Tornado 7 - Sussex
At 2:27 pm a State Trooper sighted a tornado
northwest of the town of Sussex. Trees were knocked down. At about 2:32 pm
a tornado was sighted near the town of Waverly. The tornado crossed Route
40 just south of the town and moved east-northeast through a residential
section. Most of the damage was to trees. Numerous pine trees were broken
off at rooftop level. Some hardwoods were blown over with their roots
exposed. A couple of houses had chimneys knocked off. One home had a small
branch driven into its siding. All trees were blown to the left of the
path of the storm indicating tornadic circulation. It crossed U.S. Route
460 and destroyed a peanut warehouse. The peanut warehouse was a metal
building without much in the way of supports.
The tornado was classified as an F-1 when it moved
through Waverly. The length of the damage path through Waverly was about 4
miles. The total path length from the State Trooper sighting through
Waverly was 14 miles, but much of this area is remote and it is uncertain
how much of the time the tornado was on the ground. The path width through
Waverly was 100 yards. No damage estimates were obtained.
Tornado 8 - Surry
A tornado touched down near the intersection of
Route 601 and 614 in the southwest part of the county. It was likely the
same storm that struck Waverly. The tornado moved to the northeast across
Route 615. The track was about 2.5 miles long and 150 yards wide. Numerous
trees were broken off about 15 feet up. A chimney was knocked off a
two-story house. Metal roofing was torn off a shed and outbuildings were
damaged. Near Route 615, two houses and two cars were damaged and several
trees uprooted. Tornado began as an F-0 and possibly reached the low end
of an F-1 near Route 615.
Tornado 9 - Surry
The storm produced another tornado struck near the
town of Surry. An apartment building on Route 626 west of Surry was
damaged. The roof over three units was blown off and an in-wall was pulled
away from the frame. A lot of siding was also pulled off. One car had its
windows shattered. The tornado moved northeast causing moderate damage to
trees along Route 641 just west of Route 31. Trees were also reported down
near Scotland Wharf Ferry Terminal. The tornado was seen around 3:00 pm
headed across the James River toward James City County.
The tornado was rated an F-1. The path length was
about 5 miles. The path width averaged 100 yards. Damage estimates for
Surry County (from both tornado 8 and 9) were 20,000 dollars.
Tornado 10 - James City-York
Fishermen spotted the tornado moving along the
banks of the James River and onto land at approximately 2:50 pm. The
tornado destroyed a recreation building owned by the employees on the BASF
corporation grounds. Debris was scattered through the woods. A bathhouse
was completely gone. Pine trees were snapped off.
The tornado moved into a trailer park at Blow
Flats Road. Five mobile homes were rolled over. It continued into
Innovative Marine Products where a storage trailer was thrown into a large
metal manufacturing building which was flattened. It then moved across
U.S. Highway 60 taking down many trees which blocked the interstate for
hours. The tornado was rated at the high end of an F-1.
The tornado moved into York County and onto the
southern section of the Naval Weapons Station entering a housing area.
Many trees were down damaging the recreation center and a corner of a
housing unit. Here the tornado was rated an F-0. HAM radio reported
through the SKYWARN Network that a funnel spotted near the Naval Station
and Yorktown at 3:07 pm.
Total tornado path length was about 7 to 8 miles.
Path width narrowed from 150 yards as the tornado came off the river to 75
yards near the end of its trail. Damages to James City County were about
750,000 dollars. No dollar estimate of damages were provided by the Naval
Tornado 11 - Isle of
At about 3:00 pm, a tornado was sighted at the
Franklin Airport. This is open area and no damages were reported to county
officials or the National Weather Service (NWS). About 5 miles northeast
of the airport, a man reported observing rotation within the thunderstorm
but he did not see a funnel.
Tornado 12 - Newport
At 3:10 pm, a man on the James River Bridge
reported seeing three funnel clouds over the river. He said two dissipated
and the other became a tornado moving into the woods on the Newport News
side of the river. The tornado moved northeast across Villa Road and
through a Flea Market on Jefferson Avenue. Extensive damage occurred to
expensive homes along Villa Road. Most damage was from trees falling onto
homes. The Flea Market was a poorly constructed metal building. The
tornado blew off the roof and some of the side walls. Pieces of metal
could be seen wrapped around tree tops to the left of the buildings and
for several blocks downwind.
The tornado moved northeast into the City of
Hampton. Damage was slightly less. A portable classroom at Big Bethel High
School was overturned and paneling was stripped off the end. Several air
conditioners were torn off the top of a grocery store near the
intersection of Hampton Roads Center Parkway and Interstate 64.
The tornado was
classified an F-1. The tornado path length was approximately 12 miles. The
tornado's width was 400 yards as it came off the river and it gradually
narrowed to 100 yards as it moved through Hampton. Newport News reported
163 homes damaged, 12 condemned and damage costs at approximately 1.2
million. Approximately 85 homes were damaged in Hampton, 8 condemned and
damage costs were 700,000 dollars. Eight people were injured in Newport
News and two in Hampton. There were no fatalities.
The tornado moved onto Langley Air Force Base
(AFB) mainly moving across open area and runways. Damage occurred to
several F-15s parked at the end of a runway for an air show planned for
the next day. There was also damage to a storage area. Langley AFB weather
observations reported tornado sightings on two separate occasions at least
an hour apart. The damaging tornado described was observed for
approximately 20 minutes. A second tornado path was not found, but may
have occurred over water or rural land or may have been a funnel that did
not touch down.
Tornado 13 - Middlesex
At around 3:00 pm a tornado moved through an area
near Stormont. Trees were snapped off near the landfill. A barn was
damaged along Route 629 and a travel trailer was blown over. The tornado
moved across Route 673 between Christ Church School and Locust Hill.
Estimated damage in Middlesex was 34,000 dollars. The tornado was rated an
F-0 with a path length of about 3 miles and a with of 100 yards.
Tornado 14 - Lancaster
At 3:15 pm, a tornado moved into White Stone from the Rappahonnock River
down Beach Road for about a mile. Residents saw the swirling debris. Trees
were broken off and homes were damaged from the fallen trees. Estimated
damage was 55,000 dollars and the tornado was classified an F-0. The width
of the damage path was 100 yards and it was on the ground for at least a
mile. The tornado was from the same storm that hit Middlesex County and it
may have been the same tornado.
Several vehicles were blown off the road into the
ditch near Ottoman but there was no other damage reported in that area nor
tornadoes sighted. It was therefore credited to strong thunderstorm winds.
Ottoman is located to the north of both this path and that of the
Tornado 15 - Northampton
At 3:50 pm, a tornado was sighted by several park
personnel from Kiptopeke State Park. The tornado moved through trees
breaking them off at about 15 feet up for about 100+ yards then moved over
a cliff and tracked another 700 yards making a path about half a mile
long. A second funnel was sighted over the water.
At least 105 trees were damaged or destroyed.
Picnic tables were thrown. A 20 foot ornamental boat was thrown 120 feet.
A construction trailer and another trailer were overturned. Damages ranged
to 30,000 dollars. Park officials had received NWS warnings at 3:30 pm of
the tornado threat and warned campers. Tornado was rated at the low end of
an F-1. Path width was 150 yards. This tornado likely resulted from the
same storm that struck Newport News, Hampton and Langley AFB.
Tornado 16 - Suffolk
At approximately 3:30 pm, residents hear a tornado
and saw trash and debris swirling up in their yards. Four homes were
damaged. Several trees were knocked down. Two homes under construction
were knocked off their foundation by several feet. Most of the area that
the tornado passed over was open land. This storm was rated the low end of
an F-1 with a path length of 2 miles with a width of 75 yards.
Tornado 17 - Chesapeake
Around 4:00 pm, a tornado moved through the Great Bridge area of
Cheasa-peake. It first struck along Hanbury Road near Great Bridge High
School just west of Route 168 and moved east through Etheridge Manor and
Etheridge Woods neighbor-hoods. Many residents were not at home. Those
that were heard a sound like a freight train; a few thought they saw the
funnel cloud. At least 35 homes were damaged.
The area east of
Route 168 appeared to have sustained the most damage. A brick two-car
garage was flattened, several roofs were at least partially gone and
numerous houses had the attic portion of the walls on the windward side of
their house blown out. Most of the remaining damage along the path was due
to trees being broken off and falling on houses. All downed trees and the
garage were blown to the left of the direction of the path of the tornado.
Most of the trees in this area were pine and were broken off near the
The tornado was classified an F-2 and caused an
estimated 1.8 million dollars in damage. No injuries or deaths occurred.
The path length was 2.5 miles and its width was 200 yards.
Tornado 18 - Virginia
This tornado was produced by the same storm that
produced the Chesapeake tornado. A tornado/waterspout was sighted moving
east across the bay toward the southern end of Sandbridge. At around 4:45
pm a roof was reported blown off a house at Sandpiper and Whitecap Lane in
the Sandbridge area. Two roofs were also damaged and a few trees were
broken off. Damage was minimal since this is a narrow strip of land with
only two streets along it. The tornado crossed the barrier island on a
perpendicular (or easterly) trajectory. There were few homes and few trees
with mostly beach and water in this area. A State Trooper and a few
residents spotted the tornado. The tornado was rated at the lower end of
an F-1 and the path length can only be estimated at 1.5 miles with a width
of only 50 yards.
The Meteorology Behind the Storms
An excellent overview of the meteorological
setting on 6 August 1993 was prepared by Robert Johns, the Lead Forecaster
on duty at the time at the NWS National Severe Storm Forecast Center (NSSFC)
in Kansas City. In his write-up of NSSFC actions that day, he described of
how unusual an event this was. For an outbreak or family of tornadoes to
occur in Virginia or North Carolina in mid summer, is extremely rare.
Tornadoes associated with tropical cyclones (such as hurricanes) has
occurred on a few occasions. However, records show that there has never
been a significant outbreak of tornadoes associated with an extratropical
weather system in July or August such as this one was. This type of event
typically occurs in this part of the country in late April or May or
during the fall months.
NSSFC highlighted the potential for severe weather
in their guidance to NWS forecasts offices the day prior to the outbreak.
There are three key ingredients that indicate the potential for severe
1. Instability - instability is the tendency for
the atmosphere to want to overturn. Warm, moist air near the surface will
rise and colder, drier air aloft will sink. The more unstable the air
mass, the stronger a thunderstorm's updraft will be. The stronger the
updraft, the more likely it is that the storm will produce large hail and
2. Vertical wind shear - vertical wind shear is
simply the change of wind direction and speed with height. Preferably,
winds will increase with height. This helps to strengthen a storms updraft
and tilt it downwind. A tilted updraft allows the rain to fall downwind.
The drag from the falling rain and the rain-cooled air forms a downdraft.
Because the storm is tilted, the updraft can maintain itself and the
thunderstorm is able to continue to mature. A change in wind direction
with height in a clockwise pattern encourages the initiation of rotation
in the storms updraft and also increases the storms ability to grow and
3. Lift - lift is the mechanism that will trigger
the development of thunderstorms. A strong lifting mechanism will help
intensify and focus the storms.
A low pressure center or a front is an example of
a lift mechanism.
The NWS computer models were forecasting an
unstable air mass and strong southerly winds off the surface over
Southeast Virginia for August 6. A warmfront and approaching low pressure
center would help provide the lift. The forecasting question is "will
all the ingredients come together, to what extent, and where?"
Obvious by the events of August 6, all the
ingredients did come together. A warmfront moved north of Richmond.
Widespread rain was occurring north of here while the area to the south
was destabilizing. Temperatures climbed through the seventies as the sun
peaked out from behind clouds. The air remained quite humid. Pressures
fell as a low was developing along the front over Southwest Virginia and
an upper level short-wave (disturbance) approached. Surfaces winds turned
southeast to east at 10 to 20 mph ahead of this area and yet winds at 5000
feet were from the south-southwest at 50 to 55 mph providing the ideal
vertical windshear needed for tornado development.
National Weather Service Products and
The National Weather Service (NWS) highlighted the
potential for severe weather over southeastern Virginia early that day in
a special weather statement detailing the thunderstorm potential for the
state. Virginia State Emergency Operations Center was briefed via phone
and NAWAS late that morning on the potential for the development of severe
thunderstorms and tornadoes that afternoon in Southeast Virginia. At 12:45
pm EDT, a Tornado Watch for Southeast Virginia and Northeast North
Carolina was issued. The first warning was issued for the
Petersburg-Colonial Heights-Hopewell area at 1:35 pm based on a sighting
of the Petersburg tornado along with weak radar indications from the NWS
WSR-74 radar in Volens, Virginia.
Fifteen of the 18 tornadoes occurred within the
Tornado Watch area with two more occurring very close by. Tornado Watches
always state "in and near the watch area". Approximately 13 of
the 18 tornadoes had warnings issued prior to touch down. Considering the
difficulty of identifying these storms from radar data and the initial
lack of eyewitness spotter reports to the National Weather Service, these
statistics are very good. Prior to the installation of the WSR-88D in
Sterling, few tornadoes in Virginia have been warned for prior to
touchdown. It was unfortunate on this day that the worst tornado occurred
so early in the event.
National Weather Service Radars
The National Weather Service (NWS) WSR-88D Doppler
Radar in Sterling, Virginia was too far from the storms to detect the
velocities within the thunderstorms and determine that they were rotating
and developing tornadoes. This was partially due to the widespread area of
rain between Sterling and Richmond. The Sterling radar was detecting
reflectivity (large cloud droplets and rain) from these storms. However,
Petersburg, for instance, is approximately 100 miles from Sterling. The
lowest radar beams is angled at 0.5 degrees above the horizon meaning that
as you move away from Sterling, the height of the beam increases. Add the
curvature of the earth and by the time the beam reaches the storms near
Petersburg, it is about 13,000 feet high. These storms only extended to 25
to 30 thousand feet so that the Sterling radar was only detecting the
upper most portion of the storms. This made detection of typical severe
weather and tornadic signatures very difficult.
The NWS WSR-74C in Volens, Virginia and NWS
WSR-74S at Patuxent, Maryland showed little in the way of typical radar
signatures for severe weather and tornadoes early in the event. Our
understanding and interpretation of these signatures may change some based
on this event. As the outbreak progressed and the thunderstorms moved
east, the storms began to take on a more classic look. A combination of
data from the older radars, the Sterling Doppler Radar and lightning data
was used for determining where to issue warnings as the event progressed.
Based on experience in detecting low top rotating
storms and tornadoes in northern Virginia with the Sterling radar, it is
safe to say that had the WSR-88D in Wakefield, Virginia been completed,
these storms would have been detected for what they were early in the
event with potentially warnings being issued up to 30 minutes prior to the
event. One exception was the storm that struck Petersburg. This was a new
storm growing very rapidly as it approached the City. It is believed that
at best there would have been a 15 minute warning time for downtown
Petersburg with a WSR-88D operational in Wakefield and a radar
meteorologist quick to recognize the storm for what it was. Additionally,
some of that 15 minutes would have been lost in the dissemination and
communication process of the warning before reaching the public.
The best method for increasing the accuracy and
timeliness of severe storm warnings is to have trained severe weather
spotters and emergency services personnel reporting directly to the
National Weather Service Offices severe storm sightings and damage
reports. Remember, a "Tornado Warning means that a tornado has been
sighted or is strongly indicated by radar." Forty-five minutes prior
to a tornado touching down in Petersburg was tornado damage near
Kenbridge. However, this information did not reach the weather service
until much later in the day. The tornado was sighted by people and even a
police officer, but it was not until 1:33 pm that a report of a tornado
sighted in Petersburg was relayed to the National Weather Service Richmond
Office. The meteorologist at Richmond was ready when the call came in and
a warning was immediately issued. However, for many, it was too late.
Another difficult feature of these storms for
issuing accurate warnings using radar was the storm's tremendous tilt.
What this means is that where the storm appeared on radar and where the
tornado was touching the ground was a difference of a few miles. On August
6, the storms were strongly tilting to the north. The Sterling radar
showed the storm that was producing a tornado in Dinwiddie County to
actually be over Chesterfield County.
Without spotter reports telling the specific
location of a tornado on the ground, this discrepancy with the radar
location may not be realized and a warning may be issued for the wrong
county or a city such as Petersburg may not be included in the warning
since the storm would appear to be passing north of the city. Spotter
reports and damage reports to the National Weather Service will continue
to be critical to accurate warning information even after the installation
of WSR-88D doppler radars around the state.
Once the new WSR-88D radars and new forecast
facilities are completed in the state, the NWS ability to detect and
provide early warnings will continue to improve. However, issuing a
warning is only one step in the warning process. It must also be
communicated and then properly responded to. In communications, there is a
need for an improved Emergency Broadcast System (EBS) that will alert
people who do not happen to be listening to local television or radio at
that moment. The Federal Communications Commission is working on such a
system. While Petersburg was equipped with sirens, sirens have been shown
to be ineffective in this part of the country due to the rarity that they
would be used for such an event, the frequency of malfunctions, and the
fact that some people in buildings will not hear the sirens. For that
reason, sirens in the Washington, D.C. Metropolitan Area have been taken
Even if Petersburg and Colonial Heights had had 10
to 15 minutes warning that a tornado was approaching, many people,
probably including those in Wal-Mart, would not have received the warning
and if they had, what would their reactions have been?
Despite recent severe weather awareness campaigns,
more work is needed to teach the public proper safety actions upon seeing
a tornado or receiving a warning of a tornado's approach. The actions of
Wal-Mart to move people toward the front of the store (the most vulnerable
area due to glass and doors) when the storm approached may have proven
fatal. Not only do schools need severe weather emergency plans to direct
the student body to safety, but hospitals, nursing homes, shopping malls
and businesses should all have such plans that teach those with
responsibility over others the proper actions to take in emergencies.
Some of the information used was obtained from
newspaper accountings including the Richmond Times-Dispatch, Sunday August
8, 1993, articles written by staff writers M.W. Goodwyn and Wendy Wagner,
and Beverly Orndorff. Assistance on damage surveys came from Jim Belville,
Meteorologist-in-Charge of NWS Washington, D.C. Forecast Office; Peter
Wolfe, Charlie Chillag and David Lipson of the NWS Richmond Weather
Office; Scott Stevens of the NWS Norfolk Weather Office; Roy Brit; and
John Bernier, Meteorologist with Richmond News Channel 8 for video. Robert
Johns' report from NSSFC, "Tornado Outbreak of 6 August 1993"
was used for some of the meteorological background. Steve Zubrick, Science
Operations Officer at NWS Washington Forecast Office, for helping me proof
and finalize the report and for being a Wordperfect 5.1 wiz and importing
my graphics files.
A special thanks goes to Virginia Department of
Emergency Services and the National Guard for assistance in conducting
aerial and ground level damage surveys. Also a special thanks goes to the
local emergency management officials in the independent cities and
counties impacted by the storms for their cooperation and assistance in
acquiring damage details and cost estimates and providing access to
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September 09, 2004