During the afternoon hours of April 27, 2011, an extremely powerful and fast-moving EF5 multi-vortex tornado, known commonly as the Philadelphia, Mississippi tornado or the Philadelphia EF5, touched down in eastern

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 ...

causing catastrophic damage to the northern outskirts of the town of

Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...

. Part of the historic

2011 Super Outbreak The 2011 Super Outbreak was the largest, costliest, and one of the deadliest tornado outbreaks ever recorded, taking place in the Southern, Midwestern, and Northeastern United States from April 25 to 28, 2011, leaving catastrophic destruc ...

, the largest

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 ...

on record, this was the first of four EF5 tornadoes to touch down that day and the first such storm in Mississippi since the 1966 Candlestick Park tornado. While on the ground for 30 minutes, it traveled along a path through four counties, leaving behind three deaths, eight injuries, and $1.1 million in damage. The

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 ...

thunderstorm that produced this tornado formed around 1:00 pm. CDT south of

Jackson, Mississippi Jackson is the List of capitals in the United States, capital and List of municipalities in Mississippi, most populous city of the U.S. state of Mississippi. The city sits on the Pearl River (Mississippi–Louisiana), Pearl River and is locate ...

. Traveling briskly to the northeast, it became

severe Severity or Severely may refer to: * ''Severity'' (video game), a canceled video game * "Severely" (song), by South Korean band F.T. Island See also

* * {{disambig ...

within 25 minutes and potentially tornadic by 1:36 p.m. CDT. A tornado finally touched down at 2:30 p.m. CDT just east of the

Philadelphia Municipal Airport Philadelphia Municipal Airport is a public use airport in Neshoba County, Mississippi, United States. It is owned by the City of Philadelphia and located two nautical miles (4 km) northwest of its central business district. This airp ...

. It quickly intensified and began producing EF5 damage by 2:38 pm. CDT; extreme ground scouring, up to deep in places, occurred in northeastern Neshoba County. After crossing into Kemper County, the tornado obliterated a mobile home, killing all three inside. It reached EF5 strength a second time near the Kemper–Winston county line where extreme ground scouring again took place and pavement was scoured from roads. Extensive tree damage took place elsewhere along the track and it ultimately dissipated at 3:00 p.m. CDT about north of Mashulaville.

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

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 ...

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 ...

; 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

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

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