EF0 tornado, Athens to Sweet Water, Illinois, April 15, 2011

1. EF065 to 85 mphthis tornado

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

2. EF186 to 110 mph

   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

EF0

Date

April 15, 2011

Touchdown

6:22 PM CDT (23:22 UTC)

Lifted

6:25 PM CDT (23:25 UTC)

On the ground

3 minutes

Path length

1.2 miles (2.0 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$10,000

County

Menard County

Touchdown point

39.970, -89.710

Lift-off point

39.988, -89.716

Record number

1104151722-01

25 damage points were recorded along this path by NWS ILX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 105 mph.

• Guttering and fascia ripped off. Cracked window.
• .20 feet of fence blown over.
• Outbuilding walls blown down. Full semi trailer tipped over.
• .Porch blown off of house and blown over/around house to the west side.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

A vigorous upper-level disturbance interacting with an approaching cold front triggered severe thunderstorms across central and southeast Illinois during the afternoon and evening of April 15th. The airmass ahead of the front was moderately unstable and highly sheared. As a result, several supercell thunderstorms developed along and west of the I-55 corridor. The storms produced numerous funnel clouds and three confirmed tornadoes. Hail up to 2 inches in diameter was observed as well. The storms eventually congealed into a linear structure and weakened as they pushed into east-central and southeast Illinois during the mid to late evening.

A tornado touched down in a field 1 mile northeast of Athens at 622 PM CDT. It moved north-northwest...damaging a window, siding, and gutters on a house before dissipating 2 miles north-northeast of Athens at 624 PM CDT.

A tornado touched down in a field 3 miles northeast of Athens at 625 PM CDT. It tracked northward...damaging the roof of a house, destroying a small garage, and damaging several automobiles. Further north, the tornado knocked two trees down onto a house, doing severe damage to its roof and interior walls. It then tipped over a semi-trailer and damaged several trees before dissipating 4.8 miles north-northeast of Athens at 631 PM CDT.

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

40 minutes of warning. NWS ILX issued a tornado warning for this county at 22:42 UTC, 40 minutes before the tornado touched down, in force until 23:30 UTC.

The county was under a tornado watch, issued at 17:50 UTC and running to 00:44 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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:56 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.

Springfield (SPI), 15 km from the path, in the two hours either side.

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

The Lincoln radar (KILX), 37 km away, was scanning. The volume nearest the touchdown began at 23:20 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

74 more were confirmed in the United States that day.

All 75 of them

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.