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2011 Shoal Creek Valley–Ohatchee tornado

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2011 Shoal Creek Valley–Ohatchee tornado
The large and violent tornado crossing through the Coosa River
Meteorological history
FormedApril 27, 2011, 6:28 p.m. CDT (UTC−05:00)
DissipatedApril 27, 2011, 9:15 p.m. EDT (UTC–05:00)
Duration1 hour, 47 minutes
EF4 tornado
on the Enhanced Fujita scale
Highest winds180 mph (290 km/h)
Overall effects
Fatalities22
Injuries85
Damage$366,755,000 (2011 US$)
Areas affectedMargaret, Ohatchee, Piedmont, Alabama
Part of the 2011 Super Outbreak and Tornadoes of 2011

The 2011 Shoal Creek Valley–Ohatchee tornado occurred during the evening hours of April 27, 2011, when a large and violent EF4 tornado devastated the northern portion of Ohatchee and the beachside homes on the Coosa River and many other communities in Eastern Alabama. This tornado was one of the fifteen violent tornadoes to happen during the extremely active 2011 Super Outbreak, which is the largest and costliest tornado outbreak in United States history. The long-track wedge tornado touched down a few miles northeast of Trussville and traveled 97 miles from Alabama to Georgia. Throughout its track, the tornado widened to its maximum peak width of 1,760 yards (1609 m) and peaked with an estimated wind speed of 180 mph (290 km/h); the tornado caused 22 fatalities and injured 85 people and did $367 million in damage.

Meteorological setup

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A high risk outlined for most of Alabama and parts of Mississippi, Tenneseee, and Georgia.

On April 23, the Storm Prediction Center (SPC) began monitoring the potential for a substantial severe weather outbreak in the extended range.[1] As a shortwave trough tracked across portions of the Mid-South and southeastern United States, moderate instability and strong wind shear ahead of a trailing cold front was expected to promote the development of supercell thunderstorms capable of producing tornadoes, large hail, and damaging winds.[2] Two days before the event, on April 25, the SPC issued a moderate risk of severe weather encompassing portions of central and eastern Kentucky, middle and eastern Tennessee, northeast Mississippi, central and northern Alabama, and northwest Georgia. Due to the combination of rich low-level moisture, strong shear, and focused large-scale ascent, there was relatively high confidence across the outlined area for strong tornadoes – a tornado rated EF2 or higher on the Enhanced Fujita scale – and widespread damaging winds.[3] By the morning of April 27, the SPC upgraded to a high risk of severe weather,[4] noting that a dangerous tornado outbreak capable of producing several violent – EF4 tornado or stronger on the Enhanced Fujita scale – and long-track tornadoes was expected.[5][6]

Shortly before noon, the probability of tornadoes within 25 miles of a location was increased even further to 45%, a level exceeding even typical high-risk standards, for an area including Tuscaloosa. The forecast continued to emphasize the risk of strong/violent and very damaging tornadoes, as confidence increased even further regarding the risk of an extreme, high-end tornado outbreak. Throughout the afternoon hours, in the wake of two earlier mesoscale convective systems, the air mass across western and northern portions of Alabama began to quickly destabilize, with mixed layer convective available potential energy (CAPE) estimated in the 2500–4000 j/kg range and low-level dew points of 70–72 °F (21–22 °C) surging northward from Louisiana. Meanwhile, the wind shear environment became substantially more favorable as an 80–100 kn mid-level jet ejected eastward into the region.[5] At 1:45 p.m. CDT (18:45 UTC), a Particularly Dangerous Situation (PDS) tornado watch was issued for much of Alabama, northwest Georgia, southeast Mississippi, and southern middle Tennessee, with a >95% probability of at least two tornadoes and one or more strong tornadoes.[7]

Tornado summary

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Alabama

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Remains of a home in Shoal Creek Valley

After the Tuscaloosa–Birmingham tornado dissipated northwest of Birmingham at 6:14 p.m. CDT, the supercell responsible for the tornado quickly recycled. The National Weather Service's Birmingham office issued a tornado warning at 6:18 p.m., citing the parent storm's danger and capability to produce another tornado.[8] The Shoal Creek Valley-Ohatchee tornado developed northeast of Trussville at 6:28 p.m.[9][10] In its initial EF0 phase, the tornado uprooted and snapped multiple hardwood and softwood trees.[11][12] The tornado crossed into western St. Clair County and intensified slightly as it passed immediately north of Odenville, producing EF1-level damage.[9]

Severe damage seen near the Coosa River

The tornado continued east-northeast, passing over the Beaver Creek Mountains and entering Shoal Creek Valley. Turning northeastward, the storm followed the valley's topography and its ground track more-or-less paralleled St. Clair County Road 22. Several homes with brick facades suffered major damage.[11] [9] At 7:05 p.m. CDT, the National Weather Service office in Birmingham issued a tornado emergency for northern St. Clair, northwestern Calhoun and southern Etowah counties.[13] The tornado rapidly strengthened after it crossed St. Clair County Road 26, producing EF4 damage to site-built homes, mobile homes and trees. As it approached the Coosa River, the tornado expanded to its maximum width, approximately one mile (1.6km). Crossing the river, the tornado exited St. Clair County, leaving behind $200 million in damages, 14 deaths and 20 injuries.[9][14]

The tornado was still at EF4 intensity as it crossed into Calhoun County north of Ohatchee. Where the storm crossed Alabama Highway 77, trees were debarked, numerous homes were destroyed, and mobile homes were demolished. As the tornado continued across rural northern Calhoun County, it produced EF3-level damage for several more miles. EF4-level damage was noted south of the Webster Chapel community.[11] The tornado weakened as it crossed a series of low ridges near the Calhoun-Etowah County border west of Piedmont. Damage to mobile and site-built homes indicated EF2 strength. Crossing U.S. Highway 278, the tornado weakened further to EF1 strength as it passed into Cherokee County.

In Calhoun County, the Shoal Creek Valley-Ohatchee tornado caused $126 million in damages, killed nine people and injured 25 others. The storm caused $9.4 million in damages in Etowah County, but no one was killed or hurt.[15][16][17]

After entering rural southwestern Cherokee County, the tornado again intensified, reaching EF2 strength south of Gnatville. The storm crossed Alabama Highway 9 and weakened again as it passed over hilly terrain north of Rock Run. A brief flare-up north of Bauxite produced EF3-level damage to site-built homes at Cherokee County Road 29.[11] Just as rapidly, the tornado weakened to EF1 levels as it exited Alabama. Twenty-five people in Cherokee County were injured, but no one was killed. The storm produced $19 million in damages.[18][11]

Georgia

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Entering Polk County, Georgia, the tornado immediately re-strengthened to mid-range EF2 intensity. It caused major damage to a chicken farm, along with minor-to-major damage to homes and businesses. Seven million dollars in damage were reported, with no deaths or injuries. In Floyd County, the tornado downed trees and power lines and caused light to moderate damage to homes. Four people were injured, and damages were estimated at $5 million. Finally, the tornado entered Bartow County, where it weakened further to EF1 strength, destroyed two chicken houses and brought down multiple trees and power lines. The tornado lifted a few miles southwest of Kingston, leaving no casualties but $250,000 in damages.[19][20][21]

Aftermath

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A class sign for Warrant Office Career College Class 11-17, at Fort Novosel dedicated to the April tornado victims in Shoal Creek Valley.

After the tornadoes of the 27th, Alabama's Surplus Property Division (a subdivision of the Alabama Department of Economic and Community Affairs) provided supplies for devastated communities in Calhoun County and arranged shelters for people who lost their homes in Jefferson and St. Clair counties. The agency also provided ten of thousands of bags of ice, cases of water bottles, meal kits, and boxes of tarpaulins.[22]

See also

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References

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  1. ^ Steve Goss (April 23, 2011). "Day 4-8 Severe Weather Outlook Issued on Apr 23, 2011". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  2. ^ Steve Goss (April 24, 2011). "Day 4-8 Severe Weather Outlook Issued on Apr 24, 2011". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  3. ^ Steve Goss (April 25, 2011). "Apr 25, 2011 0730 UTC Day 3 Severe Thunderstorm Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  4. ^ Ryan Jewell (April 27, 2011). "Apr 27, 2011 1200 UTC Day 1 Convective Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  5. ^ a b Ariel Cohen; Richard Thompson (April 27, 2011). "Apr 27, 2011 1300 UTC Day 1 Convective Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  6. ^ Ariel Cohen (April 27, 2011). "Public Severe Weather Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  7. ^ John Hart (April 27, 2011). "Particularly Dangerous Situation (PDS) Tornado Watch 235". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved December 7, 2013.
  8. ^ "IEM :: Valid Time Event Code (VTEC) App". mesonet.agron.iastate.edu. Retrieved 2024-08-11.
  9. ^ a b c d "Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  10. ^ "Argo-Shoal Creek-Ohatchee-Forney Tornado - April 27, 2011". 2015-04-13. Archived from the original on 2015-04-13. Retrieved 2024-07-29.
  11. ^ a b c d e "ArcGIS Web Application". apps.dat.noaa.gov. Retrieved 2024-07-29.
  12. ^ "EF1 Jefferson County: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  13. ^ "IEM :: Valid Time Event Code (VTEC) App". mesonet.agron.iastate.edu. Retrieved 2024-08-11.
  14. ^ "Argo-Shoal Creek-Ohatchee-Forney Tornado - April 27, 2011". 2015-04-13. Archived from the original on 2015-04-13. Retrieved 2024-07-29.
  15. ^ "EF4 Calhoun: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  16. ^ "EF1 Etowah: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  17. ^ "EF1 Calhoun: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  18. ^ "EF3 Cherokee County: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  19. ^ "EF2 Polk: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  20. ^ "EF2 Floyd: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  21. ^ "EF1 Bartow: Storm Events Database - Event Details | National Centers for Environmental Information". www.ncdc.noaa.gov. Retrieved 2024-07-29.
  22. ^ Tornado Recovery Action Council. "2017 report on 4/27/11" (PDF).
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