Tornado outbreak of April 9–11, 2011

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Tornado outbreak of April 9–11, 2011
April 9, 2010 Mapleton, Iowa tornado damage.jpg
Damage from the Mapleton, Iowa tornado
TypeTornado outbreak
DurationApril 9 – April 11, 2011
Tornadoes
confirmed		49
Max. rating1EF4 tornado
Duration of
tornado outbreak2		48 hours, 6 minutes
CasualtiesNone
Damage$2.2 billion
1Most severe tornado damage; see Enhanced Fujita scale
2Time from first tornado to last tornado

The tornado outbreak of April 9–11, 2011 was one of several tornado outbreaks in the U.S. to take place during the record month of April 2011. Producing 49 tornadoes across the Midwest and Southeast, 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 of these storms was an EF4 tornado that touched down south of Pocahontas, Iowa on April 9. Between 0256 and 0257 UTC (9:56 and 9:57 pm CDT) that day, five tornadoes were on the ground simultaneously in Pocahontas County, Iowa, all of which were from one supercell thunderstorm.

Throughout Iowa, damage from the storms is estimated at $78.6 million, much of which likely took place in and around Mapleton.[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]

At the same time, a progressive upper-level trough moved east out of the Rocky Mountains and over the Midwest. Owing to early morning thunderstorms, moisture levels in the central Great Plains increased; however, capping in the region would limit daytime activity before atmospheric instability allowed for severe weather. forecast models indicated that the low-level jetstream would produce significant wind shear, aiding in the formation of possible tornadic supercell thunderstorms, and CAPE (convective available potential energy) values could exceed 3,000 j/kg. In light of this, the Storm Prediction Center (SPC) stated a moderate risk of severe weather for areas around the Minnesota-Iowa border. A slight risk was also defined for a broader region surrounding the moderate as well as a narrow line extending southward to Texas.[5] A warm front began developing along the southeastern side of the low pressure area as it moved over The Dakotas.[6]

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 2250 UTC (5:50 pm 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. By 0021 UTC (7:21 pm CDT), a small tornado touched down roughly 2 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 1 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]

Cottonville, Wisconsin EF2 tornado damage, one year later

Tracking northeastward, the supercell moved into Ida County, another tornado touched down around 0115 UTC (8:15 pm CDT) to the west of Arthur.[9] This storm remained on the ground for 5 to 10 minutes, during which it damaged a few structures, before dissipating 2 miles (3.2 km) northwest of Arthur.[10] Around 0120 UTC (8:20 pm CDT), the cell entered Sac County and the first in a series of multiple tornadoes touched down northwest of Odebolt. Over the following three hours, 13 tornadoes touched down across several counties. Around 0208 UTC (9:08 pm CST), a 1.5 mi (2.4 km) wide, EF3 tornado touched down southwest of Pocahontas. Remaining on the ground for over an hour, this tornado meandered along a 30 mi (48 km) path, producing several satellite tornadoes.[11]

Officials blocked off the town and Governor Terry 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 PDS Tornado Watch was issued for parts of Minnesota, Michigan, and Iowa, as well as most of Wisconsin. With 16 confirmed tornadoes in Wisconsin, the outbreak ranks 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]

Confirmed tornadoes[]

Confirmed tornadoes by Enhanced Fujita rating
EFU EF0 EF1 EF2 EF3 EF4 EF5 Total
0 12 25 7 4 1 0 49

April 9 event[]

List of confirmed tornadoes – Saturday, April 9, 2011[nb 1]
EF# Location County / Parish State Start Coord. Time (UTC) Path length Max width Summary Refs
EF0 Norton Norton (city) VA 36°55′N 82°37′W / 36.92°N 82.62°W / 36.92; -82.62 (Norton (Apr. 9, EF0)) 1945 Unknown Two buildings were damaged and some trees were snapped.
EF0 W of Menifee, Wolfe KY 37°50′N 83°37′W / 37.83°N 83.62°W / 37.83; -83.62 (Valeria (Apr. 9, EF0)) 2000 Unknown Hundreds of trees were damaged in the Daniel Boone National Forest.
EF0 Wolfe KY 37°50′N 83°31′W / 37.84°N 83.51°W / 37.84; -83.51 (Valeria (Apr. 9, EF0)) 2005 0.25 mi (400 m) Brief tornado touchdown with a carport and barn destroyed. Two houses and a vehicle were also damaged.
EF0 Milligan College Carter TN 36°18′N 82°19′W / 36.30°N 82.32°W / 36.30; -82.32 (Milligan College (Apr. 9, EF0)) 2035 1 mi (1.6 km) Several trees were knocked down.
EF1 E of Jonesborough Washington TN 36°17′N 82°26′W / 36.29°N 82.44°W / 36.29; -82.44 (Jonesborough (Apr. 9, EF1)) 2200 3 mi (4.8 km) Three barns were heavily damaged and trees were twisted.
EF1 ENE of Washington TN 36°18′N 82°23′W / 36.30°N 82.38°W / 36.30; -82.38 (McKinley (Apr. 9, EF1)) 2208 1 mi (1.6 km) Several large trees were knocked down.
EF0 N of Unicoi TN 36°02′N 82°32′W / 36.04°N 82.54°W / 36.04; -82.54 (Rocky Fork (Apr. 9, EF0)) 2215 1 mi (1.6 km) Minor tree damage along the path.
EF0 NNE of Shelby Cleveland NC 35°22′N 81°31′W / 35.37°N 81.52°W / 35.37; -81.52 (Shelby (Apr. 9, EF0)) 2250 0.5 mi (0.80 km) Two mobile homes were flipped over, injuring one of the occupants. Several other houses sustained minor damage.
EF3 Mapleton area Monona IA 42°10′N 95°47′W / 42.17°N 95.79°W / 42.17; -95.79 (Mapleton (Apr. 9, EF3)) 0020 3.5 mi (5.6 km) Severe damage in town and a state of emergency was declared as a result of a large wedge tornado. Many houses and businesses were damaged or destroyed, representing about 60% of the town. In total, over 100 houses were destroyed. 14 people were injured.
EF1 NW of Ricketts Crawford IA 42°12′N 95°39′W / 42.20°N 95.65°W / 42.20; -95.65 (Ricketts (Apr. 9, EF1)) 0037 1 mi (1.6 km) Tornado knocked down power lines.
EF2 W of Arthur Ida IA 42°16′N 95°25′W / 42.27°N 95.41°W / 42.27; -95.41 (Arthur (Apr. 9, EF2)) 0115 4 mi (6.4 km) Several buildings, including a farm house, were heavily damaged and trees and power lines were damaged.
EF3 NW of Odebolt Sac IA 42°21′N 95°17′W / 42.35°N 95.28°W / 42.35; -95.28 (Odebolt (Apr. 9, EF3)) 0123 10.14 mi (16.32 km) Large wedge tornado damaged or destroyed several houses.
EF2 NNE of Odebolt Sac IA 42°22′N 95°14′W / 42.37°N 95.23°W / 42.37; -95.23 (Odebolt (Apr. 9, EF2)) 0129 8.34 mi (13.42 km) Numerous houses were damaged or destroyed.
EF0 SSW of Early Sac IA 42°23′N 95°12′W / 42.38°N 95.20°W / 42.38; -95.20 (Early (Apr. 9, EF2)) 0138 0.75 mi (1.21 km) Satellite tornado to the 0129 tornado remained over open country.
EF1 S of Galva Ida IA 42°29′N 95°25′W / 42.48°N 95.42°W / 42.48; -95.42 (Galva (Apr. 9, EF1)) 0142 4 mi (6.4 km) A farmstead was severely damaged with numerous outbuildings destroyed and a home losing its roof. A few other structures, including an ethanol plant, were also damaged.
EF3 SW of Pocahontas (1st tornado) Sac, Buena Vista, Pocahontas IA 42°44′N 94°54′W / 42.74°N 94.90°W / 42.74; -94.90 (Pocahontas (Apr. 9, EF3)) 0208 30 mi (48 km) 1.5 mi (2.4 km) Long-track, extremely large wedge tornado, with a damage swath 1.5 miles (2.4 km) wide, leveled several farmhouses and damaged others. Numerous farm buildings were also damaged or destroyed. Tornado remained on the ground for more than an hour. From 0256 to 0357 UTC (9:56 to 10:57 pm CDT), this was one of five tornadoes on the ground in Pocahontas County, three of which were satellite tornadoes to this.
EF0 S of Sulphur Springs Buena Vista IA 42°34′N 95°05′W / 42.57°N 95.08°W / 42.57; -95.08 (Sulphur Springs (Apr. 9, EF0)) 0214 1 mi (1.6 km) Brief tornado touchdown with no damage.
EF1 S of Cherokee Cherokee IA 42°36′N 95°32′W / 42.60°N 95.53°W / 42.60; -95.53 (Cherokee (Apr. 9, EF1)) 0220 5 mi (8.0 km) Several structures sustained significant damage along the path and corn stubble was scoured. A confinement building was also destroyed by the tornado.
EF2 SW of Pocahontas (2nd tornado) Sac, Buena Vista IA 42°32′N 94°57′W / 42.54°N 94.95°W / 42.54; -94.95 (Pocahontas (Apr. 9, EF2)) 0224 1.75 mi (2.82 km) Satellite tornado to the previous storm. Two buildings were heavily damaged.
EF1 ESE of Newell Buena Vista IA 42°35′N 94°56′W / 42.58°N 94.94°W / 42.58; -94.94 (Newell (Apr. 9, EF1)) 0225 1 mi (1.6 km) Several outbuildings and farm buildings were damaged.
EF0 SW of Alta Buena Vista IA 42°38′N 95°20′W / 42.63°N 95.33°W / 42.63; -95.33 (Alta (Apr. 9, EF0)) 0250 Unknown First brief tornado touchdown in the area with no damage.
EF0 WSW of Alta Buena Vista IA 42°39′N 95°21′W / 42.65°N 95.35°W / 42.65; -95.35 (Alta (Apr. 9, EF0)) 0250 Unknown Second brief tornado touchdown in the area with no damage.
EF4 W of Pocahontas (1st tornado) Pocahontas IA 42°43′N 94°50′W / 42.71°N 94.84°W / 42.71; -94.84 (Pocahontas (Apr. 9, EF4)) 0254 3.2 mi (5.1 km) Strongest tornado of the outbreak. One house was flattened by the tornado and swept off its foundation. A combine, estimated at 30,000 pounds (14,000 kg) was tossed roughly 100 yards (91 m) as well and many trees were debarked. [15]
EF1 WSW of Pocahontas (1st tornado) Pocahontas IA 42°41′N 94°48′W / 42.69°N 94.80°W / 42.69; -94.80 (Pocahontas (Apr. 9, EF1)) 0255 1.5 mi (2.4 km) Satellite tornado to the EF4 Pocahontas tornado. On the ground at the same time as the following tornado. Relatively minor damage.
EF1 WSW of Pocahontas (2nd tornado) Pocahontas IA 42°41′N 94°48′W / 42.69°N 94.80°W / 42.69; -94.80 (Pocahontas (Apr. 9, EF1)) 0255 1.6 mi (2.6 km) Satellite tornado to the EF4 Pocahontas tornado. Anticyclonic tornado paired with the previous cyclonic tornado. Relatively minor damage.
EF2 W of Pocahontas (2nd tornado) Pocahontas IA 42°43′N 94°48′W / 42.71°N 94.80°W / 42.71; -94.80 (Pocahontas (Apr. 9, EF2)) 0256 0.9 mi (1.4 km) Third satellite tornado to the EF4 Pocahontas tornado which was later absorbed by that violent wedge. One home was severely damaged.
EF1 W of Pocahontas (3rd tornado) Pocahontas IA 42°44′N 94°44′W / 42.73°N 94.73°W / 42.73; -94.73 (Pocahontas (Apr. 9, EF2)) 0308 2.4 mi (3.9 km) One house was damaged.
EF1 NW of St. Joseph Kossuth IA 42°55′N 94°17′W / 42.92°N 94.28°W / 42.92; -94.28 (St. Joseph (Apr. 9, EF3)) 0419 0.8 mi (1.3 km) A hog barn was damaged, numerous windows blown out and half of a shed collapsed.
Sources: NWS Sioux Falls, NWS Omaha, NWS Des Moines, NCDC Storm Data

April 10 event[]

List of confirmed tornadoes – Sunday, April 10, 2011[nb 1]
EF# Location County / Parish State Start Coord. Time (UTC) Path length Max width Summary Refs
EF1 SW of Augusta Eau Claire WI 44°38′N 91°11′W / 44.64°N 91.18°W / 44.64; -91.18 (Augusta (Apr. 10, EF1)) 2157 1.5 mi (2.4 km) Brief tornado destroyed a garage and damaged two farmsteads and a barn. Earliest tornado to touch down in Eau Claire County during the course of a year on record. Previous earliest was May 10.
EF1 NW of Augusta Eau Claire WI 44°42′N 91°09′W / 44.70°N 91.15°W / 44.70; -91.15 (Augusta (Apr. 10, EF1)) 2204 0.5 mi (0.80 km) Two outbuildings destroyed and three more damaged. Significant tree damage as well.
EF3 Merrill area Marathon, Lincoln WI 45°07′N 89°53′W / 45.11°N 89.88°W / 45.11; -89.88 (Merrill (Apr. 10, EF3)) 2308 21 mi (34 km) Severe damage in the area, especially at and around the where hangars and airplanes were destroyed. Throughout Merrill, 65 houses were damaged or destroyed. One person was thrown 200 ft (61 m) from his home after the tornado destroyed his home and he was seriously injured. One other person was injured. Overall damage was estimated at $10.8 million, most of which took place at an industrial park. [16][17]
EF2 Cottonville area Adams WI 44°02′N 89°54′W / 44.03°N 89.90°W / 44.03; -89.90 (Cottonville (Apr. 10, EF2)) 2312 17 mi (27 km) Numerous houses sustained roof damage and mobile homes were destroyed. Extensive tree damage also occurred along with barns and sheds destroyed. A camping trailer was also overturned and sheet metal was wrapped around trees. Preliminary losses from the tornado reached $2.25 million. [16][18]
EF1 SSW of Necedah Juneau WI 44°00′N 90°05′W / 44.00°N 90.08°W / 44.00; -90.08 (Necedah (Apr. 10, EF1)) 2314 4.5 mi (7.2 km) A mobile home was rolled over and pine trees were snapped.
EF1 SW of Hancock Adams, Waushara WI 44°04′N 89°40′W / 44.06°N 89.67°W / 44.06; -89.67 (Hancock (Apr. 10, EF1)) 2330 12 mi (19 km) Trees and power poles downed. Houses sustained roof damage and irrigation systems were destroyed.
EF1 SE of Parrish Langlade WI 45°24′N 89°24′W / 45.40°N 89.40°W / 45.40; -89.40 (Parrish (Apr. 10, EF1)) 2350 5.3 mi (8.5 km) Extensive tree damage along the path affecting over 1600 acres and one million trees. One cabin was destroyed.
EF1 S of Fremont Waushara, Waupaca, Outagamie WI 44°14′N 88°52′W / 44.23°N 88.86°W / 44.23; -88.86 (Fremont (Apr. 10, EF1)) 0016 30 mi (48 km) Multiple barns were destroyed and highway signs were damaged. The roof was torn off one house in Readfield and the steeple was torn off the church.
EF2 E of Argonne Forest, Florence WI 45°38′N 88°49′W / 45.64°N 88.82°W / 45.64; -88.82 (Argonne (Apr. 10, EF2)) 0030 13 mi (21 km) Extensive tree and power line damage. A roof was torn off of a home and several barns and garages were destroyed as well.
EF1 NE of Poy Sippi Waushara, Winnebago WI 44°10′N 89°00′W / 44.16°N 89.00°W / 44.16; -89.00 (Poy Sippi (Apr. 10, EF1)) 0053 14.9 mi (24.0 km) Intermittent tornado touchdown with barns and buildings damaged. Roof damage to houses occurred and extensive tree damage occurred. Crossed over Lake Poygan into Winnebago County where mobile homes were damaged and flipped.
EF1 W of Armstrong Creek Forest WI 45°39′N 88°30′W / 45.65°N 88.50°W / 45.65; -88.50 (Armstrong Creek (Apr. 10, EF1)) 0103 3 mi (4.8 km) A house was damaged and a garage was destroyed. Many trees were snapped in the area. Barns were also destroyed.
EF0 SE of Berlin Green Lake WI 43°55′N 88°53′W / 43.92°N 88.89°W / 43.92; -88.89 (Berlin (Apr. 10, EF0)) 0127 2 mi (3.2 km) Trees were snapped and a wooden structure was damaged.
EF2 Kaukauna area Outagamie WI 44°16′N 88°16′W / 44.26°N 88.26°W / 44.26; -88.26 (Kaukauna (Apr. 10, EF2)) 0143 1.5 mi (2.4 km) Over 180 houses were damaged in the community, some of them losing roofs. Large trees were uprooted or snapped. A church sustained roof damage and had air conditioning units torn off.
EF1 S of Greenleaf Brown WI 44°16′N 88°05′W / 44.27°N 88.09°W / 44.27; -88.09 (Greenleaf (Apr. 10, EF1)) 0153 1.1 mi (1.8 km) Silos were damaged and a barn roof was ripped off.
EF1 S of Stockbridge Calumet WI 44°03′N 88°17′W / 44.05°N 88.29°W / 44.05; -88.29 (Stockbridge (Apr. 10, EF1)) 0159 1.1 mi (1.8 km) Minor damage to four houses and the roof was torn off of a metal storage building.
EF0 N of Rogersville Webster MO 37°09′N 93°04′W / 37.15°N 93.06°W / 37.15; -93.06 (Rogersville (Apr. 10, EF0)) 0355 7 mi (11 km) Damage to trees and outbuildings.
Sources: NWS Twin Cities, NWS La Crosse, NWS Green Bay, NWS Springfield, NCDC Storm Data

April 11 event[]

Main article: Tornado outbreak of April 9–11, 2011
List of confirmed tornadoes – Monday, April 11, 2011[nb 1]
EF# Location County / Parish State Start Coord. Time (UTC) Path length Max width Summary Refs
EF1 NNW of Rio Vista Johnson TX 32°16′N 97°26′W / 32.27°N 97.43°W / 32.27; -97.43 (Rio Vista (Apr. 11, EF1)) 0609 1.5 mi (2.4 km) Five houses were damaged, one of them heavily and a wall was torn from a pharmacy. Mobile homes were also damaged and barns were destroyed.
EF1 Alvarado Johnson TX 32°24′N 97°13′W / 32.40°N 97.22°W / 32.40; -97.22 (Alvarado (Apr. 11, EF1)) 0622 200 yd (180 m) Five commercial buildings were damaged and mobile homes were flipped. Two people were injured.
EF1 Forney area Kaufman TX 32°35′N 96°19′W / 32.58°N 96.32°W / 32.58; -96.32 (Forney (Apr. 11, EF1)) 0713 0.5 mi (800 m) Several houses sustained roof damage and a truck stop sign was blown over.
EF1 S of Cash Hunt TX 32°59′N 96°08′W / 32.98°N 96.13°W / 32.98; -96.13 (Cash (Apr. 11, EF1)) 0734 7 mi (11 km) Two houses were heavily damaged and numerous other houses sustained lesser damage. Damage to trees and sheds as well.
EF1 Vestavia Hills Jefferson AL 33°27′N 86°47′W / 33.45°N 86.78°W / 33.45; -86.78 (Vestavia Hills (Apr. 11, EF1)) 0027 0.4 mi (640 m) Brief tornado embedded in larger microburst. One house was heavily damaged and numerous trees were snapped.\
Sources: NWS Fort Worth, NWS Birmingham, NCDC Storm Data

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.[19] Roughly 3,200 insurance claims worth $12 million were later made in the city.[20] 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.[21]

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.[22][23] 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.[21]

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.[21]

Aftermath[]

Within days of the tornadoes in Iowa, excavators were brought in to clear debris and tear down homes that were damaged beyond repair.[24] On May 5, nearly a month after the outbreak, President Barack 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.[25] This declaration is set to remain in effect until May 1, 2012.[26] 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.[27]

Notes[]

  1. ^ Jump up to: a b c All 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.

References[]

  1. ^ Nancy Gaarder (May 6, 2011). "Aid on way for April storms". Omaha World-Herald. Archived from the original on May 14, 2011. Retrieved May 14, 2011.
  2. ^ "Billion Dollar U.S. Weather/Climate Disasters". National Climatic Data Center. 2011. Retrieved November 12, 2011.
  3. ^ NWS Blacksburg (April 9, 2011). "Multiple tornadoes confirmed on April 8, 2011". National Weather Service. Retrieved April 9, 2011.
  4. ^ "Storm Reports for April 9, 2011". Storm Prediction Center. National Oceanic and Atmospheric Administration. April 11, 2011. Retrieved April 11, 2011.
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ "Tornado Damage In Monona County, Iowa, Including Mapleton". National Weather Service Office in Omaha, Nebraska. National Oceanic and Atmospheric Administration. April 10, 2011. Archived from the original on June 15, 2011. Retrieved May 14, 2011.
  9. ^ Jump up to: a b "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.
  10. ^ "Damage survey for Arthur, Iowa and Cherokee County tornado". National Weather Service Office in Omaha, Nebraska. National Oceanic and Atmospheric Administration. April 21, 2011. Retrieved May 14, 2011.
  11. ^ "Tornado Damage Survey April 9, 2011 -- Pocahontas Tornado Upgraded to EF4". National Weather Service Office in Des Moines, Iowa. National Oceanic and Atmospheric Administration. May 3, 2011. Retrieved May 14, 2011.
  12. ^ Unattributed (April 10, 2011). "Mayor: Over half of Iowa town damaged by tornado". Associated Press. Archived from the original on April 13, 2011. Retrieved April 10, 2011.
  13. ^ John Rondy (April 11, 2011). "Possible seven Wisconsin tornadoes may be record". Reuters. Archived from the original on April 14, 2011. Retrieved April 12, 2011.
  14. ^ Storms cause havoc in Ontario Archived April 25, 2013, at the Wayback Machine - The Weather Network, April 11, 2011
  15. ^ Melanie S. Welte (May 3, 2011). "Strength of tornado in Pocahontas County raised". Chicago Tribune. Archived from the original on May 4, 2011. Retrieved May 4, 2011.
  16. ^ Jump up to: a b Jeff Starck (April 11, 2011). "Merrill tornado damages 65 homes, causes millions in damages". Green Bay Press-Gazette. Archived from the original on April 12, 2011. Retrieved April 12, 2011.
  17. ^ Unattributed (April 12, 2011). "Merrill tornado causes $11M damage, hurls man 200 feet". Green Bay Post-Gazette. Archived from the original on April 13, 2011. Retrieved April 12, 2011.
  18. ^ Adam Wise (April 11, 2011). "Tornado causes more than $2 million in damage". Green Bay Post-Gazette. Archived from the original on April 12, 2011. Retrieved April 12, 2011.
  19. ^ "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.
  20. ^ Paul Gores (May 29, 2011). "Spring storms take toll on insurers". Milwaukee-Wisconsin Journal Sentinel. Retrieved May 31, 2011.
  21. ^ Jump up to: a b c "Hail, Thunderstorm Wind Damage & Thunderstorm Wind Gust events for the U.S." National Weather Service Office in San Diego, California. National Oceanic and Atmospheric Administration. April 2011. Retrieved May 31, 2011.
  22. ^ "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.
  23. ^ Shane Allen (April 13, 2011). "Strong Storms, Tornadoes Cause Estimated $100M in Damages". NBC Dallas-Fort Worth. Retrieved April 14, 2011.
  24. ^ Dolly A. Butz (April 18, 2011). "Feds, state officials tour Mapleton". Quad City Times. Archived from the original on July 3, 2018. Retrieved May 14, 2011.
  25. ^ "President Declares Major Disaster for Iowa". Federal Emergency Management Agency. May 5, 2011. Archived from the original on August 28, 2011. Retrieved May 14, 2011.
  26. ^ "Declaration Detail: M1977". Federal Emergency Management Agency. May 5, 2011. Retrieved May 14, 2011.[permanent dead link]
  27. ^ Unattributed (May 6, 2011). "SBA offers loans for tornado recovery". The Des Moines Register. Archived from the original on May 14, 2011. Retrieved May 14, 2011.
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