Storm Events Database

Event Details

Event Hail
Magnitude 1.75 in.
State IOWA
County/Area SAC
WFO DMX
Report Source Trained Spotter
NCDC Data Source CSV
Begin Date 2011-04-09 19:48:00.0 CST-6
Begin Location 1S SCHALLER
Begin Lat/Lon 42.48/-95.3
End Date 2011-04-09 19:48:00.0 CST-6
Deaths Direct/Indirect 0/0 (fatality details below, when available...)
Injuries Direct/Indirect 0/0
Property Damage 15.00K
Crop Damage 0.00K
Episode Narrative A very dynamic weather pattern set up over the central U.S. during the day on the 9th. A deep trough formed aloft over the southeast U.S. with a strong southwest flow setting up over Iowa at all levels. During the afternoon and evening, the low level jet increased steadily and reached 50 to 70 kts by midnight. Considerable moisture advection took place with surface dewpoints rising into the low to middle 60s by evening. A strong warm front lifted north into Iowa during the afternoon. By the early evening hours it extended from west central Iowa into the east central and southeast counties of the state. This front served as a focusing mechanism for thunderstorm development. A strong elevated mixed layer was in place over the state during the afternoon of the 9th. This kept convection from developing until the evening hours. The freezing level was quite high for mid April, around 13,000 feet. By early evening, at the initiation of storm development, the atmosphere had become very unstable. Lifted indices were in the -9 to -12 C range with elevated CAPE feeding into the state in the 3000 to 5000 J/kg range. The atmosphere was very sheared with effective shear of 60 to 65 kts. As the moisture increased, precipitable water values increased to between 0.8 and 1.1 inches. There was considerable downdraft CAPE available, with 1100 J/kg available. CAPE in the -10 to -30 C layer of the atmosphere was between 500 and 1000 J/kg. The effective helicity in the low layers of the atmosphere was around 800 J/Kg. The LCL was around 1250 meters. Thunderstorms developed along the warm frontal boundary during the very late afternoon and evening hours. The storms formed more as discrete supercells rather than forming into a line. The strongest supercells moved through Onawa County along the northern Crawford County line into Sac County. Another strong supercell moved through Kossuth County. In addition to the tornadoes that occurred, there were scattered reports of hail ranging from golf ball to baseball size with the storms. There were a few reports of wind damage, however most of the damage that occurred was tornadic in nature. On the north edge of the storms, what appeared to be a gravity wave lifted northeast along the back side of the line. It produced a wind gust of near 60 MPH for a short period of time in Emmet County. Several tornadoes touched down across western into northwest Iowa. In Sac County, an EF3 tornado touched down with peak winds of 140 MPH. The path length was about 13 miles long and reached a mile in width at its widest. The tornado began north of Odebolt and ended about 6 miles northwest of Early. Damage was done to a farmstead and one home was totally destroyed. Shortly before that, a tornado touched down in Crawford County from northwest of Ricketts to to about 4 miles northeast of Schleswig. Damage was done to farmsteads along its path. Another tornado touched down in Sac County northwest of Odeboldt and tracked to just northeast of Early. This tornado had winds of 132 MPH, EF2 strength, with a half mile wide peak width. It was on the ground for about 13 miles. In what was the longest tornado track of the day, about 30 miles in length, a tornado touched down just west of Nemaha and tracked to about 3 1/2 miles southwest of Havelock through Sac, Buena Vista, and Pocahontas Counties. The tornado was EF3 in strength and had a peak width of 2 to 3 miles. Major damage occurred along the route with hog buildings destroyed, several farmsteads damaged or destroyed, and residential damage reported. A turkey containment was destroyed, with the building completely removed. Numerous hogs died in the tornado was well. There were at least 4 satellite tornadoes associated with this long track tornado. Two of the satellite tornadoes were a cyclonic/anticyclonic pair as they pushed north into Pocahontas County. Another tornado, related to the same parent cell, tracked southeast and crossed paths with the long track tornado in Pocahontas County. This tornado had peak winds of 170 MPH and was rated EF4. Several farmsteads were destroyed by the tornado. The path width was nearly 600 yards wide. Yet another tornado touched down in Sac County northwest of Nemaha, and tracked to about 9 miles northeast of Nemaha. It was on the ground for about 12 miles and had a peak width of 1/2 mile. Damage was done to farms and a hog confinement building. In Kossuth County, a tornado touched down briefly south of Algona and was on the ground for about a mile. It was 200 yards wide and was EF1 strength with 90 MPH winds. A smaller tornado touched down briefly southwest of Algona in Kossuth County. Damage occurred to a hog confinement building and to power lines. Following the NWS storm survey, there were two other tracks of EF-0 strength tornadoes discovered. One occurred in farm fields of Sac County, north-northwest of Odebolt. The path was about a mile long and 200 yards wide at its widest, with peak winds estimated at 65 MPH. The tornado had an erratic track which actually looped back on itself. Another tornado touched down in farm fields in Pocahontas County. It was also an EF-0 tornado with a path length of about 2.5 miles and maximum width of 250 yards. Winds with the tornado were around 100 MPH. Governor Terry Branstad proclaimed a State Disaster Declaration for Buena Vista, Sac, Calhoun, and Pocahontas Counties.
Event Narrative Trees and power lines were also downed.


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All events for this episode:

Location County/Zone St. Date Time T.Z. Type Mag Dth Inj PrD CrD
Totals: 0 0 18.827M 0.00K
RICKETTS CRAWFORD CO. IA 04/09/2011 18:37 CST-6 Tornado EF1 0 0 25.00K 0.00K
ODEBOLT SAC CO. IA 04/09/2011 19:23 CST-6 Tornado EF3 0 0 2.000M 0.00K
ODEBOLT SAC CO. IA 04/09/2011 19:29 CST-6 Tornado EF2 0 0 1.000M 0.00K
EARLY SAC CO. IA 04/09/2011 19:38 CST-6 Tornado EF0 0 0 1.00K 0.00K
EARLY SAC CO. IA 04/09/2011 19:41 CST-6 Hail 1.75 in. 0 0 15.00K 0.00K
EARLY SAC CO. IA 04/09/2011 19:48 CST-6 Hail 1.25 in. 0 0 5.00K 0.00K
SCHALLER SAC CO. IA 04/09/2011 19:48 CST-6 Hail 1.75 in. 0 0 15.00K 0.00K
EMMET (ZONE) EMMET (ZONE) IA 04/09/2011 20:00 CST-6 High Wind 52 kts. MG 0 0 5.00K 0.00K
EARLY SAC CO. IA 04/09/2011 20:08 CST-6 Hail 2.00 in. 0 0 15.00K 0.00K
NEMAHA SAC CO. IA 04/09/2011 20:08 CST-6 Tornado EF2 0 0 2.000M 0.00K
NEMAHA SAC CO. IA 04/09/2011 20:24 CST-6 Tornado EF2 0 0 500.00K 0.00K
FONDA POCAHONTAS CO. IA 04/09/2011 20:31 CST-6 Tornado EF3 0 0 10.000M 0.00K
VARINA POCAHONTAS CO. IA 04/09/2011 20:54 CST-6 Tornado EF4 0 0 2.500M 0.00K
VARINA POCAHONTAS CO. IA 04/09/2011 20:55 CST-6 Tornado EF1 0 0 10.00K 0.00K
VARINA POCAHONTAS CO. IA 04/09/2011 20:55 CST-6 Tornado EF1 0 0 10.00K 0.00K
VARINA POCAHONTAS CO. IA 04/09/2011 20:56 CST-6 Tornado EF2 0 0 100.00K 0.00K
WARE POCAHONTAS CO. IA 04/09/2011 21:03 CST-6 Hail 1.00 in. 0 0 2.00K 0.00K
WESTVIEW POCAHONTAS CO. IA 04/09/2011 21:08 CST-6 Tornado EF1 0 0 10.00K 0.00K
POCAHONTAS POCAHONTAS CO. IA 04/09/2011 21:09 CST-6 Hail 1.50 in. 0 0 5.00K 0.00K
TENOLD WORTH CO. IA 04/09/2011 21:30 CST-6 Thunderstorm Wind 61 kts. EG 0 0 300.00K 0.00K
LAURENS POCAHONTAS CO. IA 04/09/2011 21:35 CST-6 Hail 2.75 in. 0 0 75.00K 0.00K
FERTILE WORTH CO. IA 04/09/2011 21:39 CST-6 Thunderstorm Wind 57 kts. EG 0 0 25.00K 0.00K
NORTHWOOD MUNI ARPT WORTH CO. IA 04/09/2011 22:00 CST-6 Hail 0.88 in. 0 0 0.00K 0.00K
ST JOSEPH KOSSUTH CO. IA 04/09/2011 22:19 CST-6 Tornado EF1 0 0 150.00K 0.00K
EMMETSBURG PALO ALTO CO. IA 04/09/2011 22:30 CST-6 Hail 1.00 in. 0 0 3.00K 0.00K
ALGONA KOSSUTH CO. IA 04/09/2011 22:32 CST-6 Hail 2.00 in. 0 0 50.00K 0.00K
SENECA KOSSUTH CO. IA 04/09/2011 22:51 CST-6 Hail 0.88 in. 0 0 0.00K 0.00K
LONE ROCK KOSSUTH CO. IA 04/09/2011 23:10 CST-6 Hail 1.00 in. 0 0 3.00K 0.00K
BANCROFT KOSSUTH CO. IA 04/09/2011 23:21 CST-6 Hail 1.00 in. 0 0 3.00K 0.00K
Totals: 0 0 18.827M 0.00K