In the evening hours of Friday, May 4, 2007, amid a severe weather outbreak across the central United States, a massive and violent tornado moved through Kiowa County in southwest Kansas, before impacting the city of Greensburg and causing widespread devastation. The tornado, known as the Greensburg tornado,. "Roughly nine minutes later, the EF-5 tornado thereafter known as the Greensburg Tornado (2007), would enter its eponymous town from the southwest." tracked through the area, killing 10 to 13 people and injuring 63. The tornado was the first to be rated EF5on the Enhanced Fujita scale after the retirement of the original Fujita scale in the United States on February 1, 2007.
The tornado touched down south of Greensburg at around 9:03 p.m. CDT, moving to the north while continuing to widen. It eventually entered Kiowa County, crossing U.S. Route 183, before reaching a peak width of to the south of Greensburg, entering the city after making a northwest turn. The tornado dissipated northwest of Greensburg after being on the ground for just over an hour.
Approximately 95% percent of the city was damaged or destroyed, with some form of damage to 662 structures, and monetary losses of $250million (2007USD). Kiowa County, in which Greensburg is located, was declared a federal disaster area in the immediate aftermath. Rebuilding efforts were intensive, and several major federal government agencies collaborated with state agencies to help restore the city with the goal of making it a "green town" using a long-term community recovery (LTCR) plan. The plan included requiring all buildings in Greensburg to gain Leadership in Energy and Environmental Design Platinum (LEED platinum) certification, the highest rating a building can achieve in the LEED program by utilizing sustainable design in energy, along with installing wind turbines in the city. The Kiowa County Memorial Hospital, which was destroyed by the tornado, was the first hospital in the United States to achieve carbon neutrality following its rebuilding in 2010.
The tornado greatly affected the economy and population of Greensburg. The city has difficulty attracting residents due to the cost of homes in the area, although it has become a point of interest among eco-tourists visiting to see the "green town" built by the Federal Emergency Management Agency's LTCR plan.
Climatological background
Tornadoes are common in the state of Kansas, with an average of 87 tornadoes touching down per year. Kansas sees the second-highest number of tornadoes within its state-boundaries in an average year, behind only Texas, which sees 124 on average. Kansas is located in the center of Tornado Alley, the region of the United States in which the most tornadoes occur. Cold and dry air from the Rocky Mountains and the West Coast of the United States drops into Tornado Alley, while moist subtropical air is pulled inward from the Gulf of Mexico. The cold air pushes under the warm and moist air, pushing it upward; this updraft leads to the development of thunderstorms capable of producing strong tornadoes.
Kansas has experienced seven F5 or EF5 tornadoes since 1950, the highest number recorded in any U.S. state. Research conducted by meteorologist and tornado historian Thomas P. Grazulis concluded that F5-rated tornadoes have struck Kansas since 1895. Kansas has had an estimated 4.4 tornadoes per since 1950, the third-highest frequency in the nation, after Oklahoma and Florida.
Meteorological synopses
Forecasting
The Storm Prediction Center (SPC), the agency responsible for outlining convective outlooks for weather in the United States, first hinted at a severe weather event on April 30, when a large area was denoted across much of the Great Plains where severe weather would be possible from May 3–7. The Day 3 convective outlook introduced a "slight" risk across western Kansas, Nebraska, and a small portion of northern Oklahoma. It was exclaimed in the outlook that "new TSTM development will be likely along dryline with activity becoming supercellular as ascent spreads NEWD with four corners impulse". The Day 2 convective outlook maintained the "slight" risk, while introducing a 30% probability of significant severe weather across the Great Plains, including western Kansas.
The Day 1 convective outlook added a "moderate" risk for much of Kansas and southern Nebraska. The risk was driven by a 15% "hatched" tornado risk, 30% wind risk, and a large 45% hail risk. The outlook noted that "while degree of instability suggests that large hail will be a primary concern...locally-damaging winds and isolated tornadoes can also be expected. Greatest tornado threat appears to extend from central KS NNWWD toward SWRN NEB...where backed low-level flow is supporting the greatest low-level shear."
At 5:15 p.m. a tornado watch was issued by the SPC including much of northern Texas, Oklahoma and southern Kansas.The watch was accompanied by a 50% chance of two or more tornadoes within the watch area and a 30% chance that a tornado in the watch area would be of EF2+ intensity.
Mesoscale synopsis
The environment around the convective risk area on May 4 was highly conducive for the development of severe thunderstorms, with a dryline being extant from the Texas panhandle to southwest Kansas.. "At the surface during the early evening hours of 4 May, a dryline extended from extreme southwest Kansas through the eastern Texas panhandle" The first thunderstorms developed along the dryline at 5:30 p.m. near the Texas panhandle, with convection moving northeast as more thunderstorms within a cluster developed and later moved into southern Kansas. From then till around 8:00 p.m. the storms struggled to become supercellular, although a cell within the cluster rapidly strengthened while moving through Clark County, Kansas. The cells combined into one supercell near U.S. Route 183.. "Fifty years later, on May 4, 2007, a cluster of thunderstorms developed near and just north of the Oklahoma-Kansas border south southeast of Dodge City about 7:30pm. During the next hour, the activity consolidated so that, by 8:45pm a large supercell was located southeast of Dodge City along U.S. Highway 183 that was just beginning to produce tornadoes." 60°F dewpoints were being transported into the cell through its inflow region, providing an opportunity for the cell to rapidly strengthened as it tracked northeast. Further observations revealed that the inflow region was housing extreme levels of instability, with convective available potential energy (CAPE) values of 5,100 J/kg being documented.
The first indications of a mesocyclone associated with the cell became present on the KDDC WSR-88D radar site's velocity scan at 7:50 p.m., and 8 minutes later a bounded weak echo region had become visible on the storm's northern flank. Other mesocyclones were also observed on radar, with two notable BWERs within the cell developing; one was associated with the main mesocyclone that produced the Greensburg tornado. At around 8:30 p.m., storm spotters began reporting wall clouds (cloud formations typically occurring at the base of thunderstorms).. "At 8:30pm It was at this approximate time that storm spotters in the area began reporting rotating wall clouds." The first two tornadoes spawned by the cell were photographed at 8:34 p.m., with two more tornadoes occurring within the next 13 minutes.
At 9:25 p.m., a well-defined hook echo, a radar signature often indicative of a mesocyclone within a thunderstorm, was located in southern Kiowa County. This hook echo was accompanied by the Greensburg tornado, which touched down at 9:03p.m. south of Greensburg.. "The tornado that would later strike Greensburg is on the ground under the hook (mesocyclone) and was destroying farm homes at this time."
Tornado summary Formation and track towards Greensburg The rotating supercell that later produced the Greensburg tornado was accompanied by several short-tracked tornadoes.. "It was also during this period that these multiple updrafts, BWERs, and mesocyclones produced brief and short track tornadoes." The Greensburg tornado itself, located on the westernmost side of the mesocyclone, began to rapidly strengthen shortly after touching down at 9:03p.m.. "The tornado gradually grew in size then becoming a broad truncated cone or 'wedge' shaped tornado."
As the main tornado continued through rural areas, oil tanks were destroyed, with oil strewn across pastures and a road. The very large tornado continued to grow in size as it approached the city of Greensburg from the south. The tornado then reached its maximum width of as determined by damage, nearly the size of Greensburg itself. At 9:41p.m., the National Weather Service office in Dodge City issued a tornado emergency for Greensburg, stating that "a violent tornado was on a direct path for portions of Greensburg this is an emergency situation for Greensburg".
Impact in Greensburg
The tornado weakened slightly as it entered residential areas in southern Greensburg, but remained violent, at EF4intensity, as it directly struck Delmer Day Elementary School, completely leveling a section of the building. Continuing north, the tornado completely devastated downtown Greensburg; the Greensburg City Hall and many other businesses suffered visible damage, including Fleener's Furniture Store, Dillon's Grocery Store, and Sutton's True Value Hardware Store. A motel on the west side of the city was severely damaged and vehicles were rolled and lofted by the tornado.. "However, the vast majority of vehicles had been breached by flying debris of which 48 vehicles were rolled, tumbled, or lofted." A Daylight Donuts coffee shop and the local bank were heavily damaged or destroyed by the tornado. Three schools were destroyed and electrical service to the city was cut by the tornado.. "Electrical service to the city was knocked out "
A large grain elevator in the northern part of Greensburg remained standing after being hit by the tornado, one of a few structures to survive the event. The Greensburg meteorite was found and recovered under a wall in the building which had previously housed it. The Greensburg Mennonite Church was also destroyed. Trees throughout the city were completely stripped of all bark, the greatest number of debarked trees being located near houses that sustained EF4damage.. "We found debarked trees adjacent to homes at all EF-scale levels the greatest number of debarked trees occurring near homes with EF-4ratings." EF5 damage was determined to have been inflicted to seven residences throughout Greensburg proper.. See Table 1
A damage survey conducted by Timothy P. Marshall, Joshua Wurman, and several other experts found that a total of 53houses had slid off brick foundations that anchored the homes to the ground.. "We encountered 53 homes that slid off their brick foundations." 194homes sustained EF0damage; many of these homes were located along the outer path of the tornado on the east and west side of the city.. "EF-0 damage occurred to 194 homes. These homes were located on the periphery of the damage track, along the east and west edges of the town." The survey also concluded that damage on the tornado's east side was more severe than damage of that on its west side.. "As expected, the degree of damage to homes was more severe on the east side of the tornado track than on the west side."