A severe thunderstorm outbreak affected portions of the Southern Plains and Central Mississippi Valley from the evening of October 20th through the morning of October 21st. The outbreak produced several tornadoes including an EF-3 affecting the Dallas, Texas area as well as another EF-1 crossing parts of Memphis, Tennessee. Clustered reports of damaging straight-line winds and significant hail were also reported. Extensive damage to property, vehicles and infrastructure has been reported for affected areas of Dallas. Downed trees and powerlines with variable property damage have also been reported on a more widespread basis. Affected states include Texas, Oklahoma, Missouri, Arkansas, Tennessee and Louisiana. At least four fatalities have been reported, according to media reports.
Local Storm Reports October 20-21. Source: NOAA/SPC
Physical Discussion
On Sunday October 20, a robust environment developed to enable severe thunderstorms over portions of the Southern Plains and Central Mississippi Valley. The environment included very moist, unstable air along with changing wind speed and direction with height, to enable rotating thunderstorm updrafts. Thunderstorms were initiated in this environment ahead of an upper-level disturbance and related surface system crossing the area. The best focus for thunderstorm initiation occurred during the evening of October 20th through the morning of the 21st. Thunderstorms initiated in the form of discrete supercells which began to organize into linear segments as the event progressed, with a shift from a primary tornado and hail threat the evening of the 20th to more of a straight-line wind threat by the morning of the 21st.
Severe thunderstorm activity produced reports of tornadoes, as well as clustered reports of damaging straight-line (nontornadic) wind gusts and significant hail from the Southern Plains to the Central Mississippi Valley. Specifics can be found at the U.S. Storm Prediction Center. Confirmed tornadoes reported by local National Weather Service offices include an EF-3 in Dallas along with an EF-1 in Rowlett. An EF-1 tornado was also confirmed in Christian and Webster Counties, Missouri, along with another EF-1 affecting Memphis, Tennessee.
Confirmed tornado tracks in the Dallas area. Source: NOAA/Damage Assessment Toolkit.
This outbreak is consistent with a secondary peak in severe thunderstorm activity that we typically see during the mid to late autumn months. This occurs as the boundary between warm, tropical air and cold, polar air begins to amplify and drift further south during the autumn months, consistent with a strengthening jet stream and storm track. Severe thunderstorm activity often follows storm progression along this boundary.
Impacts
At least four fatalities have been reported by media, along with several injuries. Impacts were reported in Texas, Arkansas, Tennessee, Oklahoma, Louisiana and Missouri. Light to moderate property damage was reported in affected areas, with more severe to complete damage for those sites affected by significant tornado activity. Reports of downed trees and powerlines along with power outages and transportation disruption were also widespread.
Texas
Tornado activity in the Dallas metro area has rendered significant to complete damage to affected homes and businesses according to media reports. Numerous buildings have collapsed or suffered extensive damage to roofs or exterior walls. Reports indicate that seven people escaped a structure that collapsed in northwest Dallas. In the meantime all occupants managed to escape a collapsed convenience store. Parts of an apartment complex were also completely destroyed at Glenrio Lane and Ricksaw Drive. Extensive damage was also reported at a local radio station as well as Fire Station 41 where roof collapse was reported. A Home Depot store in the area also suffered extensive damage to the roof and exterior walls, with evidence also of some deformation of steel support beams; employees were dismissed early and the store was reported vacant at the time the tornado hit. Remarkably, no fatalities have been reported to date for the area despite reports of some non-serious injuries. Dozens of affected residents were expected to shelter at a local leisure complex near Love Field Airport (which also suffered some damage). A curfew was also placed in effect for the most severely affected areas.
The storms brought extensive reports of downed trees and powerlines along with power outages affecting at least 100,000. Natural gas leaks were also reported in the most severely affected areas. The tornadoes crossed two major interstates, and significant transportation disruption was reported due to roadways blocked by debris or floodwaters. Meanwhile the DFW Airport reported flight delays and ramp closures during the event.
The Walnut Creek Elementary School, Cary Middle School and Thomas Jefferson High School all suffered significant to complete damage, and at least two of these schools are expected to be a complete loss, according to officials; at least 2,300 students will be attending classes at other schools as a result.
Impacts were also reported in Midlothian and Richardson where a number of homes were heavily damaged.
Tennessee
Severe thunderstorm activity also affected the Memphis Metro area Monday morning where numerous tornado warnings were issued. The Cottonwood Apartments southeast of Downtown Memphis sustained significant damage with complete removal of the roof. Downed trees and powerlines were reported over widespread areas along with variable property damage including the Parkway Village area. At least 30,000 lost power during the storm. Meanwhile aircraft were evacuated due to tornado warnings at Memphis International Airport and occupants were asked to shelter in airport restrooms as a precaution. Minor damage was reported at the airport.
Meanwhile downed trees and powerlines were reported in Germantown.
Arkansas
In Benton County, an apparent tornado removed the roof from a business and also damaged homes. Power poles were snapped and trees were uprooted in the area. Local officials in the area confirmed at least one fatality due to a tree that fell on a home. Meanwhile in Poinsett County, a few houses and buildings were completely destroyed including a gas station. Several injuries were reported. Damage was reported to a convenience store, an elementary school and several outbuildings in the area. Reports also indicate that a tractor trailer was overturned on nearby I-55.
Oklahoma
Reports from media and the SPC indicate extensive reports of downed trees and powerlines along with variable property damage, especially to farm structures and outbuildings. Several large trees fell onto a mobile home near Valliant, and media reports indicate at least one fatality as a result. Wind damage was also reported in Asher.
Louisiana
Tornado and wind activity produced reports of variable wind damage along with downed trees and powerlines. Near Geismer, at least one person was injured by falling bricks. An attic fire was also started due to downed powerlines near Bossier City.
Missouri
Media and SPC reports indicate downed trees in affected areas from wind and tornado activity. In Christian County, reports indicate numerous downed trees along with a power pole bent in half and variable property damage. A mobile home was also blown off its foundation near Willow Springs as a result of damaging straight-line winds.
Sources: U.S. National Weather Service, U.S. Storm Prediction Center, The Weather Channel, Associated Press, Reuters.
