F2 tornado, Gridley to Pontiac, Illinois, May 23, 2004

1. F040 to 72 mph

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

2. F173 to 112 mph

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

3. F2113 to 157 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. F3158 to 206 mph

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

5. F4207 to 260 mph

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

6. F5261 to 318 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

F2

Date

May 23, 2004

Touchdown

8:20 PM CDT (01:20 UTC)

Path length

13.1 miles (21.1 km)

Path width

240 yards (219 m)

Deaths

0

Injuries

0

Counties

McLean and Livingston counties

Touchdown point

40.720, -88.850

Lift-off point

40.870, -88.770

Record number

1157

A tornado touched down 3 miles southeast of Gridley damaging several farm buildings. It then traveled to the northeast increasing in intensity 1.5 miles south southwest of Meadows causing moderate damage to several more farm buildings. The tornado continued to intensify reaching F2 intensity right before it crossed over into Livingston County. There were no buildings on the McLean County side of the road but the survey team determined that the damage to the buildings on the Livingston County side of the road was of F2 intensity. The tornado then traveled into Livingston County (NWS Chicago's warning area). No injuries were reported.

A tornado moved into Livingston County from McLean County, 1.7 miles northwest of Chenoa. A farm house was unroofed and a double-wide mobile home, outbuildings and grain bins were destroyed. The tornado ended 8 miles southwest of Pontiac or 2.5 miles southwest of Ocoya. At its strongest point, the tornado was 240 yards wide, with wind speeds between 130 and 140 mph. For additional information on this tornado, see Storm Data for ILLINOIS, Central.

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

29 minutes of warning. NWS ILX issued a tornado warning for this county at 00:51 UTC, 29 minutes before the tornado touched down, in force until 01:45 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 01:02 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.

The Lincoln radar (KILX), 84 km away, was scanning. The volume nearest the touchdown began at 01:21 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 2004 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

9 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.