1Most severe tornado damage; see Enhanced Fujita scale 2Time from first tornado to last tornado
One of several tornado outbreaks in the United States to take place during the record month of April 2011, 49 tornadoes were produced across the Midwest and Southeast from April 9–11. Widespread damage took place; however, no fatalities resulted from the event due to timely warnings. In Wisconsin, 16 tornadoes touched down, ranking this outbreak as the state's largest April event on record as well as one of the largest single-day events during the course of any year. The strongest tornado of the outbreak was an EF4 tornado that touched down west of Pocahontas, Iowa on April 9, a short-lived satellite to a long-track EF3 tornado. Between 0256 and 0258 UTC (9:56 and 9:58 p.m. CDT) that day, five tornadoes were on the ground simultaneously in Pocahontas County, Iowa, all of which were from one supercell thunderstorm. Other tornadoes impacted parts of eastern Kentucky and Tennessee on April 9, hours before the event in Iowa.
Throughout Iowa, damage from the storms was estimated at $78.6 million, much of which likely took place in and around Mapleton, which was struck by an EF3 tornado on April 9.[1] In addition to the tornadoes, Texas experienced a widespread straight-line wind and hail event, leaving $100 million in damage. Overall, losses from the storm system reached $2.2 billion, making it the third of a record sixteen billion dollar disasters in 2011.[2]
Meteorological synopsis
A large storm system with an associated frontal boundary moved northward and eastward across the central United States beginning on April 8. While initial severe weather was limited, a lone supercell broke out ahead of a mesoscale convective system in Pulaski County, Virginia on the eastern end of the warm front that evening. Two tornadoes were confirmed, one of which was an EF2 that caused severe damage in Pulaski, Virginia. Numerous houses were damaged and eight people were injured.[3] An outbreak began across the United States during the afternoon of April 9; supercells developed along the warm front and tracked through parts of Kentucky, Tennessee, Virginia, and North Carolina, generating softball sized hail and eight more tornadoes.[4]
Picture of an EF2 tornado west of Arthur, Iowa on April 9.
During the evening hours of April 9, the SPC issued a tornado watch for western and northern Iowa, eastern Nebraska and southeast South Dakota. Conditions within this region were favorable for the development of multiple tornadic storms and there was a 70 percent chance of multiple touchdowns.[7] Around 22:50 UTC (5:50 p.m. CDT), a strong thunderstorm developed over Burt/Cuming Counties in northeastern Nebraska. This cell slowly tracked east-northeastward and developed into a supercell as it moved into Monona County, Iowa. At 00:20 UTC (7:20 p.m. CDT), a small tornado touched down roughly two miles (3.2 km) southwest of Mapleton. Within minutes, this storm quickly grew and intensified as it moved closer to the city. The tornado passed directly over the city at low-end EF3 strength. Turning northward, the tornado dissipated about one mile (1.6 km) north of Mapleton. A separate EF2 tornado struck the town of Early, where considerable damage occurred to homes and businesses.[8]
Tracking northeastward, the supercell moved into Ida County, another tornado touched down around 01:20 UTC (8:20 p.m. CDT) to the west of Arthur.[9] This storm remained on the ground for eight minutes, during which it damaged a few structures, before dissipating two miles (3.2 km) northwest of Arthur.[10] Around the same time, the cell entered Sac County and the first in a series of multiple tornadoes touched down northwest of Odebolt. Over the following three hours, 14 tornadoes touched down across Sac, Buena Vista, and Pocahontas counties. At 02:08 UTC (9:08 p.m. CST), a 1.5-mile (2.4 km) wide EF3 tornado touched down in northern Sac County. Remaining on the ground for an hour, this tornado meandered along a 30-mile (48 km) path, producing several satellite tornadoes, including a short-lived EF4 tornado west of Pocahontas.[11]
Officials blocked off the town and GovernorTerry Branstad issued a disaster proclamation for the town. Early estimates indicated that 60% of the town was damaged and 20% was nearly flattened. Despite the damage, only three people sustained minor injuries.[12]
On April 10, another moderate risk was issued. A PDSTornado Watch was issued for parts of Minnesota, Michigan, and Iowa, as well as most of Wisconsin. With 16 confirmed tornadoes in Wisconsin, the outbreak ranked as the largest single-day event in April in the state. Severe damage occurred in the towns of Merrill, Kaukauna, and Cottonville.[13] On the evening of April 10, a number of tornado watches and warning were issued stretching from southern Oklahoma to Sault. Ste. Marie, Michigan as well as central Ontario which became Canada's first tornado watch of the season. Thunderstorm watches and warnings were also reported as far away as northern and northwestern Ontario.[14]
A well-constructed barn lifted and moved, a well-anchored carport was destroyed, and many large trees were twisted or uprooted. Two houses and a vehicle were also damaged.[16]
Two mobile homes were flipped over, injuring three of the occupants in one. Several houses sustained minor structural damage, and other mobile homes received mainly minor underskirting and roof damage. The roof was blown off a vehicle shed, and trees were downed.[19]
A large tornado caused severe damage in Mapleton. Over 100 homes and businesses were damaged or destroyed, representing about 60% of the town. Most garages and other small structures were destroyed, large trees were uprooted, and windows were blown out of vehicles. Fourteen people were injured. A state of emergency was declared as a result of the tornado.[23]
This tornado occurred between Arthur and Ida Grove, where two grain bins and two outbuildings on a farmstead were either heavily damaged or destroyed, and a house and garage sustained shingle damage. Several trees were downed, and power poles and lines were damaged.[25]
A large wedge tornado damaged or destroyed several houses and downed power lines. It initially moved northeast toward Early before making a sharp turn north-northwest to just east of Schaller. This tornado occurred simultaneously to and just west of the following tornado.[26][27]
This tornado formed as a satellite to the previous tornado. It executed a brief loop and then moved due north before dissipating. It remained primarily over open country.[26][29]
A farmstead was severely damaged, with numerous outbuildings destroyed and a home losing its roof. Outbuildings at another farmstead were damaged, as was an outbuilding at an ethanol plant. At least five power poles were snapped, and trees were downed as well.[30]
A very large, long-tracked wedge tornado leveled several farmhouses and damaged several others. Numerous farm buildings, silos, farm equipment, and livestock shelters were also damaged or destroyed. Numerous power poles and lines were blown down, along with many trees. The tornado remained on the ground for an hour and reached a maximum width of 1.5 miles (2.4 km) in Pocahontas County. It was associated with six satellite tornadoes, including two simultaneous in Buena Vista County and four simultaneous in Pocahontas County, with five tornadoes on the ground at one time from 02:56–02:58 UTC. This tornado took a very erratic path, turning eastward and northward along a northeasterly track, producing an unusual and varying debris field; the track ended just west-southwest of Havelock.[26][31]
Several outbuildings were damaged or destroyed on two farmsteads, a camper was flipped into a garage, causing damage to both, a large anchored empty tank was flipped, and several buildings in a livestock confinement area were heavily damaged. A house sustained roof damage and broken windows, a grain bin was blown into a semi truck, and a semi trailer was flipped onto another grain bin. Several trees were snapped or uprooted, corn stubble was scoured, and power poles and lines were damage.[33]
This was the first satellite tornado to the long-track EF3 tornado that began at 02:08 UTC. The tornado moved due east before hooking to the north-northwest into Buena Vista County and dissipating. Farm buildings were heavily damaged, and trees were downed.[26][34]
The strongest tornado of the outbreak, rated low-end EF4, was an intense satellite tornado that occurred on the west flank of the large EF3 wedge tornado that began at 02:08 UTC. The tornado moved to the east-southeast, absorbing the 02:56 UTC EF2 tornado that formed as another satellite. One house was flattened and swept off its foundation by this tornado. A combine, estimated at 30,000 pounds (14,000 kg), sitting in a machine shed was tossed roughly 100 yards (91 m), and many trees were debarked.[26][38][39]
This satellite tornado to the long-track EF3 wedge tornado was on the ground at the same time as the following tornado. Relatively minor damage occurred. Both tornadoes moved generally northward just to the southeast of the 02:08 parent EF3 tornado and the 02:56 UTC EF2 satellite.[26][40]
This satellite tornado to the long-track EF3 wedge tornado was an anticyclonic tornado paired with the previous cyclonic tornado. Relatively minor damage occurred. Both tornadoes moved generally northward just to the southeast of the 02:08 parent EF3 tornado and the 02:56 UTC EF2 satellite.[26][41]
This satellite tornado to the long-track EF3 wedge tornado took a curved path northward on the west side of the parent tornado and was quickly absorbed by the eastward moving EF4 satellite. One home was severely damaged.[26][42]
One house was damaged as the tornado remained over mostly open fields. This tornado occurred east of the track of the 02:08 UTC EF3 wedge tornado that had just dissipated to the northwest.[26][43]
Two farmsteads were impacted, with many trees downed. At one, a garage was destroyed, and a barn was heavily damaged as well. This was the earliest tornado to touch down in Eau Claire County on record; the previous earliest was May 10.[45]
Severe damage occurred on the north side of Merrill, especially at and around the Merrill Municipal Airport, where hangars and airplanes were destroyed. Throughout Merrill, 65 houses and 12 businesses were damaged or destroyed, with several homes losing nearly all exterior and some interior walls. One person was thrown 200 feet (61 m) after the tornado destroyed his home; he sustained serious injuries. Another person sustained minor injuries. An industrial park sustained heavy damage, and a few other homes and barns were damaged outside of Merrill. Many trees were downed along the path as well.[47][48][49]
Numerous houses sustained roof and structural damage, and mobile homes were either heavily damaged or destroyed, along with barns and sheds. A camping trailer was also overturned and sheet metal was wrapped around trees. A lake association building was completely destroyed, a cement silo was knocked over, vehicles were flipped, and numerous center-pivot irrigation systems were twisted or destroyed. Numerous trees were downed along the path.[47][50][51]
Several houses sustained roof damage, the roof was torn off a mobile home, and several center-pivot irrigation systems were destroyed. Trees and power poles were downed as well.[53]
This tornado produced extensive tree damage along the path, affecting over 1,600 acres (6.5 km2) and knocking down or damaging over one million trees. One cabin was destroyed by falling trees.[54]
Multiple barns and other farm buildings were heavily damaged or destroyed, and highway signs were damaged. The roof was torn off a house in Readfield, and the steeple was torn off a church. Many trees were snapped or uprooted along the path.[55]
Hundreds of trees were snapped or uprooted, some of which fell on cabins. A roof was torn off of a home, several barns and garages were destroyed, and power lines were downed as well.[56]
Near Poy Sippi, a house was damaged, and a barn was destroyed. Along the north shore of Lake Poygan, another barn was flattened. Near Boom Bay in Winnebago County, two homes lost portions of their roofs, while several other houses sustained minor damage. Two small mobile homes were rolled as well. Many trees were snapped or uprooted along the path.[57]
Lawn furniture was sucked from under a porch and thrown against a fence, an outdoor spa was damaged, and a wooden structure received light damage. Trees and tree branches were snapped as well.[59]
Over 180 houses were impacted in Kaukauna, several of them losing large sections of their roofs. In total, seven homes were destroyed, 24 homes and four businesses sustained major damage, and 160 other homes sustained minor damage. A church sustained roof damage and had air conditioning units torn off, and large trees were snapped or uprooted.[60]
A waterspout moved onshore from Lake Winnebago and damaged two homes. A three-season room on one of the houses was ripped off the structure. It also tore off a section of the roof of a large metal outbuilding and snapped the tops of trees.[62]
Five houses were damaged, one of them heavily, and a wall was torn from a pharmacy. A garage was shifted off its foundation, and several trees were downed.[64]
Eight homes, a pipe manufacturing plant, and two metal buildings were damaged in Cash, while four U-Haul trailers were blown across the highway. Several more homes sustain mainly minor roof damage to the northeast of Cash, although one home sustained significant damage to the roof and second story. Northwest of Lone Oak, five mobile homes were damaged or destroyed, and another site-built home sustained significant damage. Trees were downed along the path.[67]
This brief tornado was embedded in a larger microburst. Several homes and other buildings were damaged, mostly by falling trees, and the windows were blown out of a vehicle. Numerous trees were snapped or uprooted as well.[68]
Non-tornadic events
Accompanying the tornadoes, large hail and high winds also impacted parts of the Midwest. Initially, these events associated with the outbreak were confined to Iowa and parts of Nebraska and Minnesota on April 9. In Iowa, hail was measured up to 3.5 in (8.9 cm) in diameter, resulting in some damage to homes and cars.[9] On April 10, a large line of severe storms produced damage from northern Minnesota southward to the Texas-Mexico border. Most damage along this line resulted from straight-line winds; however, Wisconsin, 2 to 2.5 in (5.1 to 6.4 cm) diameter hail in La Crosse broke windows, dented cars and damaged homes.[69] Roughly 3,200 insurance claims worth $12 million were later made in the city.[70] Elsewhere in the state, winds up to 65 mph (105 km/h) downed numerous trees and power lines and in some instances tore roofs of buildings.[71]
In Texas, winds as high as 95 mph (153 km/h) caused extensive damage to homes and businesses, resulting in roughly $100 million in damage.[72][73] Numerous trees were felled across the region and a few structures were destroyed. In Dallas County, a few carports collapsed. Near Venus, 82 mph (132 km/h) winds damaged five homes.[71]
On April 11, a strong derecho brought widespread damage to much of northern Alabama as well as parts of Mississippi, Georgia and Tennessee. Near Brent, Alabama, a wind gust of 110 mph (180 km/h) was recorded 70 ft (21 m) up on a radio tower.[71]
Aftermath
Within days of the tornadoes in Iowa, excavators were brought in to clear debris and tear down homes that were damaged beyond repair.[74] On May 5, nearly a month after the outbreak, PresidentBarack Obama signed a federal disaster declaration for Buena Vista, Cherokee, Ida, Monona, Pocahontas and Sac Counties in Iowa. This allowed for government aid to be sent to the region and aid in recovery efforts.[75] The declaration remained in effect until May 1, 2012.[76] A disaster outreach center was opened on May 6 at the Mapleton City Hall and the American Legion Post in Varina and would remain open through May 26. At these places, residents would be allowed to apply for small business and homeowner loans up to $2 million and $200,000 respectively.[77]
^ abcAll dates are based on the local time zone where the tornado touched down; however, all times are in Coordinated Universal Time and dates are split at midnight CDT for consistency.
^ abcAll damage totals are in 2011 USD unless otherwise stated.
^"Storm Reports for April 9, 2011". Storm Prediction Center. National Oceanic and Atmospheric Administration. April 11, 2011. Retrieved April 11, 2011.
^Mark Darrow and Melissa Hurlbut (April 9, 2011). "Apr 9, 2011 0600 UTC Day 1 Convective Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved April 14, 2011.
^Elizabeth Stoppkotte and John Hales (April 9, 2011). "Apr 9, 2011 1630 UTC Day 1 Convective Outlook". Storm Prediction Center. National Oceanic and Atmospheric Administration. Retrieved April 14, 2011.
^Sarah Corfidi (April 9, 2011). "Tornado Watch 116". Storm Prediction Center. National Oceanic and Atmospheric Administration. Archived from the original on 19 April 2011. Retrieved May 14, 2011.
^ ab"April 9, 2011 Storm Reports". Storm Prediction Center. National Oceanic and Atmospheric Administration. April 19, 2011. Archived from the original on 19 April 2011. Retrieved May 14, 2011.
^"April 10, 2011 Storm Reports". Storm Prediction Center. National Oceanic and Atmospheric Administration. April 20, 2011. Archived from the original on 14 June 2011. Retrieved May 31, 2011.
^"April 10-11, 2011 North Texas Severe Storms". National Weather Service Office in Fort Worth, Texas. National Oceanic and Atmospheric Administration. April 13, 2011. Retrieved May 31, 2011.
