F0 tornado, Brookville to Polo, Illinois, May 12, 1999

1. F040 to 72 mphthis tornado

   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 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. 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

F0

Date

May 12, 1999

Touchdown

3:45 PM CDT (20:45 UTC)

Path length

1.0 miles (1.6 km)

Path width

20 yards (18 m)

Deaths

0

Injuries

0

County

Ogle County

Touchdown point

42.050, -89.650

Lift-off point

42.020, -89.620

Record number

271

A series of strong slow moving thunderstorms hit western Ogle County. Funnel clouds or weak landspout tornadoes were reported southeast of Brookville and northwest of Polo. As many a 4 were spotted. There was no damage. Golf ball size hail was reported south of Forreston. The storms dumped heavy rain over parts of western Ogle County from mid afternoon well into the evening hours. Doppler radar indicated as much as 6 and a half inches of rain fell in a couple hours. The heavy rain caused flooding of low areas and creeks. Highway 64 was closed due to high water. The most serious flooding was along Pine Creek. The flooded creek washed out 3 sections of Lowell Park Road and two bridges. A car was stranded by rising flood waters on a bridge on Lowell Park Road. The driver had to be rescued by a tractor. Flooding of Pine Creek caused damage to White Pines State Park. A bridge was washed out. Flood waters swept about 30 picnic tables away. Two homes across the road from the park were flooded. The deck of one house was washed away.

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.

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 General Thunderstorms Risk. The outlook in force was issued at 19:33 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), 33 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), 91 km away, was scanning. The volume nearest the touchdown began at 20:42 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.

The live radar over the trackEvery 1999 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

4 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.