EF1 tornado, Forreston to Polo Radio Ranch Arp, Illinois, May 22, 2011

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF1

Date

May 22, 2011

Touchdown

6:28 PM CDT (23:28 UTC)

Lifted

6:31 PM CDT (23:31 UTC)

On the ground

3 minutes

Path length

1.7 miles (2.7 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

Property damage

$50,000

County

Ogle County

Touchdown point

41.974, -89.570

Lift-off point

41.974, -89.538

Record number

1105221728-01

Severe thunderstorms moved across many areas of northern Illinois during the afternoon and evening hours of May 22nd. Heavy rain produced flash flooding in some areas and tornadoes were reported with some of the strongest storms that moved across far northern Illinois during the early evening hours.

A tornado touched down just east of Forreston, on Columbine Road near Illinois Route 72 in Ogle County. The tornado continued to the northeast with a near continuous path into Winnebago County. A mobile home lost part of its roof with walls partially collapsed in Adeline. Another double wide home lost a portion of its roof on Leaf River Road at Myrtle road. A couple of utility poles were also snapped or leaning over. The tornado crossed into Winnebago County on East Montague Road near South Conger Road.

The tornado touched down south of unincorporated Polo, just south of the intersection of Union Road and Judson Road. The roof of a cattle shed was blown off along Judson Road. Several beef cattle were in the shed and one was injured severely enough it had to be euthanized. A power pole on the east side of Union Road was blown down, leaning over the road toward the west. At this point the tornado was rated low end EF1 with winds estimated at 85-90 mph. The tornado widened slightly as it progressed to the east along Judson Road, and uprooted a 20 inch diameter fir tree. At this point the tornado was still at EF1 strength, and there were branches down. The tornado then moved east and its width widened to its maximum 200 yards. There was roof damage to sheet metal roofing on 4 buildings and a wood outbuilding that was left leaning over by the tornado. In this area several 2x4���s were speared into the ground from different directions and insulation was plastered on the east and northeast face of buildings. Another property just to the northeast of this point experienced six 16 inch diameter Norway Spruce trees snapped off, and a new wood power pole was snapped in half. It was here where the tornado reached its maximum intensity with winds at 100 mph. The tornado continued to the east maintaining its intensity (EF1 strength) another quarter mile to the east where a grain bin was ripped off its foundation and a portion of the roof blown off to the north up against a fence. After this the winds weakened as the tornado lifted. A couple of additional grain bins were blown over, small branches snapped off, and shingles blown off roofs. Winds were estimated at 70-80 mph. The tornado lifted at 10506 Judson Road at Bailey Road.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.

The county was under a tornado watch, issued at 19:05 UTC and running to 04:29 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Moderate Risk, with a 0.15 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 20:00 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Sterling Rockfal (SQI), 28 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Quad Cities radar (KDVN), 94 km away, was scanning. The volume nearest the touchdown began at 23:27 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2011 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

47 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.