EF2 tornado, Merrimac to Warnock, Illinois, April 30, 2010

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 mph

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

3. EF2111 to 135 mphthis tornado

   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

EF2

Date

April 30, 2010

Touchdown

8:50 PM CDT (01:50 UTC)

Lifted

8:57 PM CDT (01:57 UTC)

On the ground

7 minutes

Path length

7.2 miles (11.6 km)

Path width

350 yards (320 m)

Deaths

0

Injuries

0

County

Monroe County

Touchdown point

38.350, -90.350

Lift-off point

38.419, -90.248

Record number

1004301950-01

Storms developed ahead of a strong cold front during the afternoon and evening hours. Numerous reports of severe weather were received including large hail, damaging winds and tornadoes.

A tornado touched down about a mile and a quarter south southeast of Kimmswick on the Illinois side of the Mississippi River. It travelled to the northeast for about 7 miles before lifting and dissipating. Several large trees were blown down just west the levee in a two and a half mile area along the path. The greatest degree of damage occurred on County Road 200E just south of the intersection with Merrimac Road. The roof of a two story home was approximately 80 percent removed. A second roof to a porch was totally removed and blown to the north northeast. Window and siding damage was also observed. Several trees and large limbs at the back of this home were severely damaged and helped to show a large convergent damage pattern. Two other homes west of the first home sustained varying degrees of damage. Roof, window and siding damage was common on these two homes. A large hanger at Jacobs Field, northeast of the home damage, sustained varying degrees of damage. Large sections of the hanger's metal roof were blown a quarter to half a mile to the north northeast. The tornado continued to damage small to medium sized machine sheds and caused minor damage to a few homes along the rest of its path. No injuries were reported.

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

29 minutes of warning. NWS LSX issued a tornado warning for this county at 01:21 UTC, 29 minutes before the tornado touched down, in force until 02:00 UTC.

The county was under a tornado watch, issued at 19:40 UTC and running to 02:03 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 00:58 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.

Cahokia/St Louis (CPS), 24 km from the path, in the two hours either side.

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

The St Louis radar (KLSX), 48 km away, was scanning. The volume nearest the touchdown began at 01:48 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 2010 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

24 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.