In the evening hours of April 27, 2011, a violent and long-tracked multi-vortex tornado impacted several communities along a path through northern

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

and southeast

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

, including

Ringgold, Georgia Ringgold is a city in and the county seat of Catoosa County, Georgia, United States. Its population was 3,414 at the 2020 census. It is part of the Chattanooga metropolitan area. History Ringgold was founded in 1846 and incorporated as a city i ...

Apison, Tennessee Apison is an unincorporated community and census-designated place (CDP) in Hamilton County, Tennessee, United States. It is a rural area east of the city of Chattanooga Chattanooga ( ) is a city in Hamilton County, Tennessee, United State ...

and

Cleveland, Tennessee Cleveland is the county seat of, and largest city in, Bradley County, Tennessee. The population was 47,356 at the 2020 United States census, 2020 census. It is the principal city of the Cleveland metropolitan area, Tennessee (consisting of Bradle ...

. The tornado, which was on the ground for 52 minutes and became known as the Ringgold–Apison tornado or The Monster, killed over twenty people while having windspeeds that were estimated to have been as high as . The tornado was part of the largest outbreak of tornadoes in recorded history, and was the deadliest to hit Georgia during the outbreak. The tornado touched down in rural

Catoosa County, Georgia Catoosa County is a county in the Northwest region of the U.S. state of Georgia. According to the 2020 census, the population was 67,872. The county seat is Ringgold. The county was created on December 5, 1853. The meaning of the Cherokee la ...

near Rock Spring, where it slowly intensified and damaged trees before crossing

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and entering into Ringgold, where it damaged several commercial buildings and later residential homes. Nine people were killed in Ringgold as the tornado devastated the town at EF3 intensity, and hundreds of buildings were destroyed before the tornado crossed into

Hamilton County, Tennessee Hamilton County is a County (United States), county located in the U.S. state of Tennessee. It is located in the southern part of East Tennessee on the border with Georgia (U.S. state), Georgia. As of the 2020 United States census, 2020 census, ...

before impacting Apison, where eight people were killed and EF4 damage was inflicted to several homes.

Meteorological synopsis

Setup

The environmental conditions leading up to the 2011 Super Outbreak were among the "most conducive to violent tornadoes ever documented". On April 25, a vigorous upper-level

shortwave trough A shortwave or shortwave trough is an embedded kink in the trough / ridge pattern. Its length scale is much smaller than that of and is embedded within longwaves, which are responsible for the largest scale (synoptic scale) weather systems. Sho ...

moved into the Southern Plains states. Ample instability, low-level moisture, and

wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...

all fueled a significant

tornado outbreak A tornado outbreak is the occurrence of multiple tornadoes spawned by the same Synoptic scale meteorology, synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least ...

from

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

; at least 64 tornadoes touched down on this day. An

area of low pressure In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with inclem ...

consolidated over Texas on April 26 and traveled east while the aforementioned shortwave trough traversed the

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

and

Ohio River The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi Riv ...

valleys. Another 50 tornadoes touched down on this day. The multi-day outbreak culminated on April 27 with the most violent day of tornadic activity since the

1974 Super Outbreak The 1974 Super Outbreak was one of the most intense tornado outbreaks on record, occurring on April 3–4, 1974, across much of the United States. It was one of the deadliest tornado outbreaks in U.S. history. It was also the most violent t ...

. Multiple episodes of tornadic activity ensued with two waves of

mesoscale convective system A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale conv ...

s in the morning hours followed by a widespread outbreak of

supercell A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms (su ...

s from

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

during the afternoon into the evening. Tornadic activity on April 27 was precipitated by a 995

mbar The bar is a metric unit of pressure defined as 100,000 Pa (100 kPa), though not part of the International System of Units (SI). A pressure of 1 bar is slightly less than the current average atmospheric pressure on Earth at sea ...

(

hPa The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an S ...

; 29.39

inHg Inch of mercury (inHg, ″Hg, or in) is a non- SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. It is the pressure exerted by a column of mercury in h ...

) surface low situated over

Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...

and a deep, negatively tilted (aligned northwest to southeast) trough over

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

and

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

. A strong southwesterly surface jet intersected these systems at a 60° angle, an ageostrophic flow that led to

storm-relative helicity {{Short pages monitor