1999 Dover–Hennessey tornado
F4 Tornado in Dover, OK
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In the evening hours of May 3, 1999, a violent high-end F4 tornado struck the town of Dover, Oklahoma, causing US$2.5M (1999 USD) in damages,[1] with the northern part of town taking a direct hit, damaging and destroying about one-third of the homes and buildings in town.[2][1] Occurring as part of a larger tornado outbreak occurring over the region, it was on the ground for 28 minutes, traveling approximately 15 miles (24 km) and had a peak width of 880 yards (800 m), resulting in the death of 1 resident and over 11 injuries.[3]
Counter-clockwise from the top: The tornado near the town of Dover; A Doppler weather radar velocity screenshot of the mesocyclone that produced the tornado over the city of Dover; A map of all Kingfisher County tornadoes since 1950 (note Dover in the center) | |
| Meteorological history | |
|---|---|
| Formed | May 3, 1999, 9:10 p.m. CDT (UTC−05:00) |
| Dissipated | May 3, 1999, 9:38 p.m. CDT (UTC−05:00) |
| Duration | 28 minutes |
| F4 tornado | |
| on the Fujita scale | |
| Max width | 880 yards (0.50 mi; 0.80 km) |
| Path length | 15 miles (24 km) |
| Highest winds | 207–260 mph (333–418 km/h) |
| Overall effects | |
| Fatalities | 1 |
| Injuries | 11 |
| Damage | $2.5 million (1999 USD) |
| Areas affected | Kingfisher County, Oklahoma, especially Dover and parts of Hennessey, Oklahoma |
Part of the 1999 Great Plains tornado outbreak and tornadoes of 1999 | |
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The tornado formed at 9:10 p.m. Central Daylight Time (CDT) in the middle of Kingfisher County, about 4 miles south-southwest of Dover,[1][4] causing minor damages, though slowly growing in width.[2][1] Shortly before crossing a nearby river, it rapidly grew in width to its peak width,[2] and upon reaching Dover, massive devastation occurred on the northern part of the town, with many mobile homes wiped off the ground.[1] After the tornado had fully passed Dover, it continued northeast, where it was tracked headed for east of Hennesey. During the tornado's move northeast and final stages, a smaller, short-lived tornado formed beside it, causing F1 damage.[1][2] Then, after about 28 minutes of being on the ground, the tornado dissipated. During its lifetime, it caused 11 injuries, one death, and the destruction of 34 structures.[1]
Meteorological synopsis
The Dover tornado was part of a much larger outbreak which produced 71 tornadoes across five states throughout the Central Plains on May 3 alone, along with an additional 25 that touched down a day later in some of the areas affected by the previous day's activity (some of which were spawned by supercells that developed on the evening of May 3), stretching eastward to the Mississippi River Valley. The most prolific tornadic activity associated with the May 3 outbreak – and the multi-day outbreak as a whole – occurred in Oklahoma; 14 of the 66 tornadoes that occurred within the state that afternoon and evening produced damage consistent with the Fujita scale's "strong" (F2–F3) and "violent" (F4–F5) categories, which, in addition to the areas struck by the Bridge Creek–Moore tornado family, affected towns such as Mulhall, Cimarron City, Dover, Choctaw and Stroud.[5]
Setup
The outbreak was caused by a vigorous upper-level trough that moved into the Central and Southern Plains states on the morning of May 3. That morning, low stratus clouds overspread much of Oklahoma, with clear skies along and west of a dry line located from Gage to Childress, Texas. Air temperatures at 7:00 a.m. Central Daylight Time ranged in the mid to upper 60s °F (upper 10s to near 20 °C) across the region, while dew point values ranged in the low to mid 60s °F (mid to upper 10s °C).[6] The Storm Prediction Center (SPC) in Norman, Oklahoma, a division of the National Weather Service, initially issued a slight risk of severe thunderstorms early that morning stretching from the Kansas-Nebraska border to parts of southern Texas, with an intended threat of large hail, damaging winds and tornadoes.[7] By late morning, the low cloud cover began to dissipate in advance of the dry line, but during the afternoon high cirrus clouds overspread the region, resulting in filtered sunshine in some areas that caused atmospheric destabilization. The sunshine and heating, combined with abundant low-level moisture, combined to produce a very unstable air mass. Upper air balloon soundings observed strong directional wind shear, cooling temperatures at high atmospheric levels, and the increased potential of CAPE values potentially exceeding 4000 J/kg, levels that are considered favorable for supercells and tornadoes.[8]
Forecast and initiation
As observations and forecasts began to indicate an increasing likelihood of widespread severe weather conditions even more favorable for strong tornadoes, the SPC issued a moderate risk of severe weather at 11:15 a.m. CDT for portions of Kansas, Oklahoma and Texas along and near the Interstate 40 corridor.[9]
... N CENTRAL TX/OK/SRN KS ...
LOW LEVEL JET WILL MAINTAIN SIGNIFICANT INFLOW OF LOW LEVEL MOISTURE WITH SURFACE DEWPOINTS AROUND 65F. CLEARING SKIES EVIDENT ON VISIBLE IMAGES WILL FURTHER CONTRIBUTE TO STRONG DESTABILIZATION OVER REGION WITH LATE AFTERNOON MUCAPES FORECASTED FROM 3500 TO 4500 J/KG OVER MDT RISK AREA. AS SHORT WAVE APPROACHES WRN OK/TX BORDER…LIFTING WILL DEEPEN NEAR/ALONG DRYLINE WITH THUNDERSTORMS INCREASING AS THEY MOVE EWD INTO INSTABILITY AXIS. 50 KT MID LEVEL SWLY FLOW SPREADING OVER LOW LEVEL JET AXIS WILL PROVIDE SUFFICIENT SHEAR FOR A FEW STRONG OR VIOLENT TORNADIC SUPERCELLS GIVEN THE ABUNDANT LOW LEVEL MOISTURE AND THE HIGH INSTABILITY.
— NWS Storm Prediction Center (SPC), May 3, 1999 1630 UTC Day 1 Convective Outlook
At 3:49 p.m. CDT, the SPC, having gathered enough data to surmise that there was a credible threat of a significant severe weather outbreak occurring within the next few hours, amended its Day 1 Convective Outlook to place the western nine-tenths of the main body of Oklahoma, central and south-central Kansas and the northern two-thirds of Texas under a high severe weather risk, denoting a higher than normal probability of strong (F2+) tornadoes within the risk area.[10] About 40 minutes after the revised outlook's issuance, at 4:30 p.m. CDT, the SPC issued a tornado watch for western and central Oklahoma, effective from 4:45 p.m. until 10:00 p.m. CDT that evening, for the threat of tornadoes, hail up to three inches (7.6 cm) in diameter, wind gusts to 80 mph (130 km/h) and intense lightning. As that happened, the first thunderstorm cell of the unfolding event had already formed over southwestern Oklahoma.[8][11]
Tornado summary
Thunderstorm formation
The supercell thunderstorm that produced the Dover tornado, designated "E", formed south-southwest of Blaine County, Oklahoma.[3] It began to grow in strength as it promptly tracked northeast, with rotation being detected early in life.[3] Then, thunderstorm "E" produced a squall line ranging from Geary, Oklahoma, to Hennessey, Oklahoma not long afterwards, with rotation prominently strengthening, before becoming hightly tornadic, having produced various mesocyclones and tornadoes, such as an F3 tornado that had struck a well-built home. Soon after the F3, the thunderstorm had recycled and produced another mesocyclone, tracking for an hour.[3]
The supercell produced 7 tornadoes and hail from 1.75 to 2.75 inches (4.4 cm to 6.9 cm) in diameter.[12]
Tornado formation
The long-tracked mesocyclone rapidly strengthened, with a Mesocyclone Strength Index (MSI) value of 7,477 measured.[13] Then at 9:10 p.m. CDT, shortly after the strong F3 that hit Altona, Oklahoma,[4] the 6th tornado of thunderstorm "E" touched down a mile west of Route 81, 4 miles south-southwest of Dover, Oklahoma in central Kingfisher County.[3][1] It tracked north, not damaging any major structures, though was intensifying.[14] In this phase, the tornado inflicted F1 damage mainly against outbuildings, trees, and telephone poles.[1][2] It then began to grow in size as it followed along Route 81, and started to shift east towards the Cimarron River, where Dover was ahead.[2]
Dover
Approaching the Cimarron river, the tornado began to rapidly grow to its maximum width of 880 yards (0.50 mi; 0.80 km) and shifted towards the town's direction rapidly.[2][4] As it neared Dover, it rapidly began to strengthen.[2] After spotting the tornado vortex signature on Doppler weather radar velocity, the Kingfisher County Emergency Management director commanded local law enforcements of Dover,[14] such as fire department and police forces, to traverse the streets with their sirens to warn all residents of the town of Dover to take shelter, as the town did not have a tornado siren.[14][15] Ten to twenty minutes after the warnings, the tornado had arrived, passing through the western part of town.
Upon entering the western part of Dover, the tornado inflicted F3 damage, then intensifying to high-end F4 intensity, with 34 mobile homes, 56 houses, and other various structures were either damaged or blatantly destroyed, including a steel-reinforced concrete home with all of its walls completely swept away.[16][17][1] The tornado had toppled around 100 powerlines, causing a massive power outage for the town.[18] Trees were found either with heavy loss of branches and stripped of all of their bark, or mobile home frames forcefully wrapped around them.[19]
The local elementary school and high school were reportedly heavily damaged by the storm, with the tornado causing $300K (1999 USD) in damages to the schools of Dover.[20][21] A woman chose to not take immedient action after the warnings, and was killed after the storm collapsed her large frame home, marking the first and only fatality of the storm.[1] The tornado also damaged the town's local baseball scoreboard.[22]
In total, around eleven were injured and one was killed. The tornado had caused around $2.5M (1999 USD) in damages, with one-third of the town devastated by the storm.[1][4]
Dissipitation
After its passing over Dover, it continued northeast of the town, crossing Route 81 into open fields. It began to weaken significantly, though it somewhat maintained its width.
At 9:30 p.m. CDT (UTC–05:00), A smaller satellite tornado formed alongside the F4, headed north-northeast towards Hennessey, Oklahoma, though was short-lived and inflicted F1 damage.[1][2] Then, the Dover tornado rapidly weakened, and eventually dissipated 8 minutes later, roping out 4 miles east-southeast of Hennessey.[2][1]
In total, the Dover-Hennessey tornado was tracked for 15 miles, had a maximum width of 0.5 miles (0.8 km), and lasted 28 minutes.[1]
Aftermath
After the storm's passing, on May 4, 1999, at around 5:10 p.m. CDT (UTC–05:00), the National Weather Service in Norman, Oklahoma released a Public information statement on the tornado outbreak, officially rating the Dover tornado F4 on the Fujita scale after damage surveys concluded.[17]
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK 510 PM CST TUE MAY 4 1999
...MORE PRELIMINARY INFORMATION ON THE MAY 3 TORNADO OUTBREAK IN CENTRAL OKLAHOMA...
SURVEYS BY NOAA METEOROLOGISTS CONTINUE THIS AFTERNOON...AND WILL RESUME ON WEDNESDAY...HOWEVER PRELIMINARY SURVEY RESULTS INDICATE THAT A PORTION OF THE TORNADO DAMAGE FROM THE BRIDGE CREEK AREA WEST OF NEWCASTLE...INTO THE EAST LAKE ESTATES DEVELOPMENT IN SOUTHWEST OKLAHOMA CITY IS IN THE F5 CATEGORY. THIS IMPLIES WIND SPEEDS IN EXCESS OF 260 MPH. THIS WAS PART OF THE TRACK PRIOR TO MOORE AND MIDWEST CITY.
ANOTHER VIOLENT TORNADO...RATED F4...OCCURRED AT DOVER IN KINGFISHER COUNTY. A THIRD VIOLENT TORNADO...ALSO RATED F4...OCCURRED THREE MILES EAST OF CRESCENT.
A NUMBER OF OTHER SITES HAVE BEEN SURVEYED...INCLUDING...
SEMINOLE COUNTY...ONE F2 AND TWO F1 TORNADOES FROM ABOUT ONE MILE EAST OF PINK TO THE NORTHWEST SIDE OF SHAWNEE...TO JUST SOUTH OF MEEKER IN LINCOLN COUNTY.
LOGAN COUNTY...F3 DAMAGE FROM JUST SOUTH OF CIMARRON CITY TO MULHALL...WITH THE F4 DAMAGE EMBEDDED EAST OF CRESCENT.
KINGFISHER COUNTY...IN ADDITION TO THE F4 AT DOVER...F3 DAMAGE STARTING ABOUT 8 MILES SOUTHWEST OF DOVER. TWO OTHERS...RATED F1...FROM A FEW MILES NORTHEAST OF GEARY INTO SOUTHWEST KINGFISHER COUNTY. ANOTHER...RATED F0...ABOUT 4 MILES LONG...WEST AND NORTHWEST OF OKARCHE.
CADDO AND GRADY COUNTIES... THE START OF AT LEAST TWO TRACKS IN THE VICINITY OF ANADARKO ARE STILL BEING SURVEYED...BUT INITIAL RATINGS ARE IN THE F1 RANGE. THE START OF THE TRACK LEADING INTO BRIDGE CREEK WAS RATED F3 TO F4 FROM WEST TO NORTH OF CHICKASHA.
— The National Weather Service, Norman, OK, 1150 AM CST May 4th 1999 Public information statement
Due to the tornado's destruction of the powerlines, the entire town had no power for two days before they could repower the town with generators.[18] During debris removal, Dover had replaced their storm warning system by buying a tornado siren from the town of Stillwater. The tornado had uprooted and heavily damaged almost all trees in nearby parks, causing the Oklahoman Forestry Department to heavily replant and landscape.[23] After the tornado, The Red Cross had set up a tent within the Dover Christian Church, to aid the injured.[18]
President Bill Clinton signed a major disaster declaration for eleven Oklahoma counties on May 4. In a press statement by the Federal Emergency Management Agency (FEMA), then-director James Lee Witt stated that, "The President is deeply concerned about the tragic loss of life and destruction caused by these devastating storms."[24] The American Red Cross opened ten shelters overnight across central Oklahoma, housing 1,600 people immediately following the disaster. By May 5, this number had lowered to 500. Throughout May 5, several post-disaster teams from FEMA were deployed to the region, including emergency response and preliminary damage assessment units. The U.S. Department of Defense deployed the 249th Engineering Battalion and placed the U.S. Army Corps of Engineers on standby for assistance. Medical and mortuary teams were also sent by the U.S. Department of Health and Human Services.[25] By May 6, donation centers and phone banks were being established to create funds for victims of the tornadoes.[26]
On May 12, FEMA also declared that seven counties, Canadian, Craig, Grady, Lincoln, Logan, Noble and Oklahoma, were eligible for federal financial assistance.[27] By May 13, roughly $1.6 million in disaster funds had been approved for housing and businesses loans.[28] This quickly rose to more than $5.9 million over the following five days.[29] By May 21, more than 3,000 volunteers from across the country traveled to Oklahoma to help residents recover.[30] With a $452,199 grant from FEMA, a 60-day outreach program for victims suffering tornado-related stress was set up to help them cope with trauma.[31]
Applications for federal aid continued through June, with state approvals reaching $54 million on June 3. By this date, the Army Corps of Engineers reported that 964,170 cubic yards (737,160 m3), roughly 58%, of the 1.65 million cubic yards (126 ha-m) of debris had been removed.[32] Assistance for farmers and ranchers who suffered severe losses from the tornadoes was also available by June 3.[33] After more than a month of being open, emergency shelters were set to be closed on June 18.[34] On June 21, an educational road show made by FEMA visited the hardest hit areas in Oklahoma to urge residents to build storm cellars.[35] According to FEMA, more than 9,500 residents applied for federal aid during the allocated period in the wake of the tornadoes. In all, disaster recovery aid for the tornadoes amounted to roughly $67.8 million by the end of July 2.[36]
See also
- List of North American tornadoes and tornado outbreaks
- List of tornadoes in the 1999 Great Plains tornado outbreak − a chronological list of the tornadoes (as compiled in National Weather Service damage surveys and local storm reports) that occurred over the seven-day period of the outbreak from May 2 to 5, 1999
- 1999 Bridge Creek–Moore tornado - a violent F5 tornado that struck areas elsewhere in Oklahoma just hours earlier