In the evening hours of May 3, 1999, a violent high-end F4 tornado struck the western portion town of Dover, Oklahoma, causing $2.5M (1999 USD) in damages, with about one-third of the homes and buildings in town demolished by the tornado. Occurring as part of a larger tornado outbreak occurring over the region, it was on the ground for 28 minutes, travelled approximately and had a peak width of , and was the cause of 1 death and over 11 injuries.
The tornado touched down at 9:10 p.m. Central Daylight Time (CDT) in the middle of Kingfisher County, about south-southwest of Dover, causing minor damage, though slowly growing in width. Shortly before crossing a nearby river, it rapidly grew in width to its peak width, and upon reaching Dover, massive devastation occurred in the western part of the town, with many mobile homes swept away. After the tornado had fully passed Dover, it continued northeast, where it tracked into open fields near Hennesey. As the tornado neared the end of its path, a smaller, short-lived satellite tornado formed beside it, producing only F1 damage. Then, after about 28 minutes of being on the ground, the tornado dissipated.
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.
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).Meteorological Summary of the Great Plains Tornado Outbreak of May 3-4, 1999 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. 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.
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.
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. 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 in diameter, wind gusts to and intense lightning. As that happened, the first thunderstorm cell of the unfolding event had already formed over southwestern Oklahoma.
Tornado summary
Thunderstorm formation
The supercell thunderstorm that produced the Dover tornado, designated "E", formed south-southwest of Blaine County, Oklahoma. It began to grow in strength as it tracked northeast, with mesocyclones detected early in life. Shortly afterwards, thunderstorm E produced a squall line ranging from Geary, Oklahoma to Hennessey, Oklahoma.
The thunderstorm's mesocyclonical rotation grew to be tornadic, with it producing its first tornado "E1" which was brief and produced F0 damage. The second tornado, "E2" tracked northeast, though inflicted F1 damage. The third tornado, "E3" was a strong tornado that struck the small community Altona, Oklahoma as it produced high-end F3 damage, dissipating west-northwest of Kingfisher, Oklahoma. Tornado "E3" most notably had multiple satellite tornadoes, such as "E4" and "E5". Shortly after tornado "E3" produced, the thunderstorm's mesocyclone had recycled, tracking for an hour before producing the Dover tornado, "E6", then it's satellite, "E7", before the thunderstorm's dissipation.
The supercell overall produced 7 tornadoes and hail in diameter.
Formation and Dover The now recycling thunderstorm's mesocyclone steadily began to become tornadic once again, with a Mesocyclone Strength Index (MSI) value of 7,477 recorded. Then at 9:10 p.m CDT, shortly after tornado "E3" dissipated, The thunderstorm finally produced the 6th tornado, touching down a mile west of Route 81, south-southwest of Dover, Oklahoma at F1 intensity. It tracked northeasternly, not damaging any major structures, though was intensifying. The tornado at this point was producing weak damage at F1 intensity, mainly against outbuildings, trees, and telephone poles. Shortly afterwards, It began to progressively grow in width as it tracked along Route 81, shifting eastward onto a path through the Cimarron River, where Dover was ahead. Approaching the Cimarron river, the tornado began to rapidly grow to its maximum width of and shifted more eastward towards the town as it intensified. After spotting the tornado vortex signature (TVS) on Doppler weather radar velocity, the Kingfisher County Emergency Management director commanded local law enforcements of Dover, 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. Ten to twenty minutes after the warnings, the tornado had arrived, passing through the western part of town.
As the tornado entered the southwestern part of Dover at F3 intensity, 34 mobile homes, 56 houses, and other various structures were either damaged or blatantly swept away. The tornado also completely levelled over 100 powerlines, causing a large-scaled power outage for the town. Trees were also found with either heavy loss of branches, stripped of bark, or mobile home frames forcefully wrapped around them. Residents reported the tornado to have sounded like a freight train or an aircraft's jet engine.
The local elementary school and high school were reportedly heavily damaged by the tornado, with it inflicting $300K (1999 USD) in damages towards the schools of Dover. A woman chose to not take immedient action after the warnings, and was killed after the storm collapsed her large frame home, the first and only fatality of the weather event. The tornado also reportedly damaged the town's local scoreboard reserved for baseball. As the tornado continued northeastward, tracking outside of Dover, the tornado struck a steel-reinforced concrete two-story frame home, completely sweeping its walls away at F4 intensity.
Satellite and dissipitation
After passing Dover, it continued northeast of the town, crossing Route 81 into the open fields. As it moved through northeastern Kingfisher County, it began to slowly weaken in strength, though somewhat maintained its width.
At 9:30 p.m CDT, A smaller satellite tornado began forming alongside the Dover tornado, tracking an opposite direction, moving north-northeast towards Hennessey, Oklahoma. This minor tornado then dissipated just south of Hennesey, only ever producing F1 damage. Afterwards, the Dover tornado began decreasing in size and strength, eventually roping out and dissipating 8 minutes later east-southeast of Hennessey.
In total, the Dover-Hennessey tornado was tracked for , had a maximum width of , caused 11 injuries and 1 fatality, caused $2.5 million (1999 USD) in damages, and lasted 28 minutes.
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 classifying the Dover tornado an F4 rating on the Fujita scale after damage surveys concluded.
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. During debris removal, Dover had replaced their storm warning system by purchasing a tornado siren from the town of Stillwater, Oklahoma. The tornado had uprooted and heavily damaged almost all trees in nearby parks, causing the Oklahoman Forestry Department to heavily replant and landscape. Classes were cancelled until power was restored in the schools.
President Bill Clinton signed a major disaster declaration for eleven Oklahoma counties on May 4, including Kingfisher. 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." The American Red Cross opened ten shelters overnight across central Oklahoma, including one within the Dover Christian Church, housing a total of 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. By May 6, donation centers and phone banks were being established to create funds for victims of the tornadoes.
On May 12, FEMA also declared that seven counties, Canadian, Craig, Grady, Lincoln, Logan, Noble and Oklahoma, were eligible for federal financial assistance. By May 13, roughly $1.6 million in disaster funds had been approved for housing and businesses loans. This quickly rose to more than $5.9 million over the following five days. By May 21, more than 3,000 volunteers from across the country traveled to Oklahoma to help residents recover. 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.