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2011 Cordova–Blountsville tornado

EF4 tornado that struck central Alabama in 2011

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Through Mississippi and Pascal (unit)

The tornado first moved through northeast Pickens County, where it strengthened while impacting structures at EF0 and EF1 intensity, moving past several smaller towns. As the tornado moved into Cordova it reached EF3 intensity and heavily damaged the town. The tornado continued to strengthen as it moved across Alabama, reaching EF4 intensity as it passed northwest of Sumiton. The tornado retained this intensity as it caused sporadic damage across rural Alabama, destroying numerous homes and debarking trees. It dissipated south of Red Hill, after being on the ground for over two hours.

The tornado was the second tornado of at least EF3 intensity to hit Cordova on April 27, and the town was devastated by both. Four people were killed in the downtown Cordova, and several businesses and homes were obliterated by the tornado as it moved through the area.

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 moved into the Southern Plains states. Ample instability, low-level moisture, and wind shear all fueled a significant tornado outbreak from Texas to Tennessee; at least 64 tornadoes touched down on this day. An area of low pressure consolidated over Texas on April 26 and traveled east while the aforementioned shortwave trough traversed the Mississippi and Ohio River 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. Multiple episodes of tornadic activity ensued with two waves of mesoscale convective systems in the morning hours followed by a widespread outbreak of supercells from Mississippi to North Carolina during the afternoon into the evening.

Tornadic activity on April 27 was precipitated by a 995 mbar (hPa; 29.39 inHg) surface low situated over Kentucky and a deep, negatively tilted (aligned northwest to southeast) trough over Arkansas and Louisiana. A strong southwesterly surface jet intersected these systems at a 60° angle, an ageostrophic flow that led to storm-relative helicity values in excess of 500 m2s−2—indicative of extreme wind shear and a very high potential for rotating updrafts within supercells. Ample moisture from the Gulf of Mexico was brought north across the Deep South, leading to daytime high temperatures of 77 to 81 °F (25 to 27 °C) and dewpoints of 66 to 72 °F (19 to 22 °C). Furthermore, convective available potential energy (CAPE) values reached 2,500–3,000 J/kg−1.

Forecast

On the morning of April 27, a strong cold front with several areas of embedded low pressure extended from the Texas Hill Country northeastward towards the Arklatex and the Ozarks, and later into the lower Ohio Valley. Warm moist air was in place due to strong southerly flow ahead of the front over Mississippi, Alabama, and Tennessee. An upper level disturbance sparked a broad area of showers and thunderstorms as it moved across the frontal boundary on the previous evening. The eastern edge of the line of showers and storms continued to move eastward, in concert with the upper disturbance, reaching the northwest Alabama border around 2:00 a.m. CDT.

This produced the last and most violent round of severe weather, which began around 2:30 p.m. CDT for northern Alabama as supercells began to line up to the southwest of the area. During the early afternoon hours, the potential for destructive tornadoes was highlighted by the Storm Prediction Center's upgrade to a high risk for severe weather around 1:00 p.m. CDT. This prompted a particularly dangerous situation (PDS) tornado watch, which was issued for northern Alabama and portions of southern Tennessee at 1:45 p.m. CDT. The bulletin that accompanied the watch read:

THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF: MUCH OF ALABAMA, NORTHWEST GEORGIA, SOUTHEAST MISSISSIPPI, SOUTHERN MIDDLE TENNESSEE, EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 145 PM UNTIL 1000 PM CDT.

...THIS IS A PARTICULARLY DANGEROUS SITUATION...

DESTRUCTIVE TORNADOES...LARGE HAIL TO 4 INCHES IN DIAMETER. THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

The potential for tornadoes ramped up from noon through 9:00 p.m. CDT. During this period, much of Alabama experienced numerous supercell thunderstorms that produced violent tornadoes, including five EF4s tornadoes, one being the Central Alabama tornado.

Cordova EF3 tornado

Prior to the Central Alabama tornado, a large EF3 tornado crossed areas that would be hit hours later, including Cordova. The tornado touched down near Fairview, where it would reach EF3 intensity as it destroyed a home to the south of Cedar Lake. The tornado continued to move in a northward direction, inflicting EF1 damage to trees as it moved to the east of Pleasant Field. After passing to the west of Drifton, the tornado moved northward, tracking directly into downtown Cordova. The tornado damaged numerous brick buildings in the area and uprooted several trees before lifting a short distance north of the town.

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