EF1 Tornado — Taylor, Iowa

2011-05-11 · near Lenox, Taylor, Iowa

Event narrative

This was the second tornado to move through Lenox on this day. This tornado formed on the southwest edge of town and moved due north into town along State Highway 49. It removed a roof from an old house and produced tree damage along its path. Shortly after removing the roof, the tornado began moving to the northwest and continued on this path prior to dissipating northwest of town. Maximum winds around 95 mph.

Wider weather episode

A very warm and humid airmass was in place over Iowa on the 11th. During the previous two days, strong capping was in place across the state. A cold front began to move into the state on the 11th as upper level heights and temperatures began to fall. The front stalled however, and the atmosphere became unstable due to the cooling aloft. The freezing level was relatively low on the 11th as it fell to under 12,000 feet. Most unstable CAPE was in the 1500 to 2500 J/kg range by the afternoon as lifted indices fell to -4 to -7 C. The atmosphere exhibited weak shear with 25 kts or less of effective shear during the afternoon. The potential was there for high winds, as well as hail, with downdraft CAPE in the 500-900 J/kg range, and CAPE in the -10 to -30 C layer of the atmosphere between 100 and 400 J/kg. Helicity values in the 0-1 km layer increased sharply over southwest Iowa and were between 100 and 200 by mid to late afternoon. In addition, considerable moisture pooling took place with precipitable water values increasing to 1.3 to 1.6 inches over the southwest half of Iowa by evening. The LCL level was quite high initially, around 1500 meters, but lowered to between 500 and 1000 meters by mid to late afternoon as continued convection moistened the atmosphere. An initial round of thunderstorms moved through the state during the morning of the 11th. Thunderstorms continued to develop intermittently over southwest Iowa during the late morning into the afternoon. The thunderstorms became more organized by mid to late afternoon as an upper level disturbance moved into the state from the south. Thunderstorms became stronger and produced several tornadoes in Adams and Taylor Counties. There were two brief touchdowns reported that caused no damage. One was in Taylor County near Sharpsburg, the other near Kent in Adams County. Two tornadoes moved through the town of Lenox in Taylor County. The first tornado touched down in south central Lenox along South Maple Street, between West Platte Street and West Iowa Street Before moving north in a curving path until it reached Walnut Street. The tornado then moved generally due north, along Walnut Street, eventually dissipating about one block north of West Van Buren Street around 1540 CST. The damage path was generally diffuse with tree damage and shingles removed from buildings. The greatest damage occurred along North Main Street, where two brick buildings received roof and upper facade damage. A second tornado moved into Lenox a short time later. The tornado touched down in the southwest part of Lenox near the intersection of State Highway 49 and West Platte Street, only a couple blocks southwest of the touchdown location of tornado number 1. The tornado traveled northward along State Highway 49, with the greatest damage occurring shortly after touchdown along Highway 49 between West Iowa Street and West Illinois Street. In that area, one house sustained damage to a second story dormer. Also in that area, a manufactured home on a foundation had approximately one half of its roof removed. The tornado then continued north along State Highway 49 generally causing tree damage and shingles to be removed from roofs. Eventually the tornado turned northwest just north of West Temple Street where an older home which housed a business had its roof removed. Shingle and tree damage continued as the tornado tracked northwest before finally exiting Lenox along Van Buren Street west of North Spear Street. The tornado continued over open fields before dissipating about

one half mile northwest of Lenox around 1548 CST. There was considerable damage done in the town of Lenox over a 35 square block area. Damage was in the millions of dollars. Reports indicated that at least 45% of the homes in the city of 1407 people were damaged by the tornadoes. One hundred and sixty trees were downed as well. The next day, Governor Terry Branstad proclaimed a Disaster Declaration for Taylor County. In addition to the tornadoes, there were numerous reports of high winds and hail. Most of the hail was around an inch in diameter with the largest report being around 2 inches in diameter in Adams County. After the storms began to weaken and move out of southwest Iowa, they produced high winds with several reports of 60 to 65 MPH winds. Heavy rainfall of 2 to 4 inches occurred in parts of southwest and south central Iowa with rainfall rates exceeding 2 inches per hour. Flash flooding occurred in Union, Adams, and Taylor Counties. Numerous roads were flooded and became impassible, along with a few state highways. Soil erosion was severe, especially in Taylor County. The heavy rainfall occurred during the worst possible time, right after planting. The soil had been freshly plowed and much of it was loose. Damage from soil erosion was many times more costly than the damage caused by the tornadoes. As the storms moved through the Johnston area, lightning struck outside of a house. The lightning entered the house via an invisible dog fence, causing a small fire inside of the house as the control unit was set on fire. Lightning struck a house in Creston. The lightning started fire, resulting in $40,000 in damage.

View location on OpenStreetMap → (40.8784, -94.5653)

Source: NOAA Storm Events Database, event_id 290637. Narrative written by the NWS forecast office that issued the report.