F4 Blue Ash tornado, Ohio, April 9, 1999

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 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 mphthis tornado

   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

F4

Date

April 9, 1999

Touchdown

5:12 AM EDT (09:12 UTC)

Path length

10.0 miles (16.1 km)

Path width

270 yards (247 m)

Deaths

4

Injuries

65

Property damage

$85 million

Counties

Hamilton and Warren counties

Touchdown point

39.230, -84.370

Lift-off point

39.300, -84.230

Record number

850

A tornado began with F2 intensity in Blue Ash in the northeast corner of the county. This tornado moved through Montgomery, Symmes Township, and Loveland before entering Warren county. The intensity of the tornado was F2 and F3 at many points along the track, intensifying to a low end F4 while in Montgomery. The width of the tornado ranged from 100 yards to 1/4 mile wide. Four fatalities occurred; two in a home and the other two in vehicles. About 91 homes and apartments were destroyed along with 37 businesses. Additionally, 197 homes and apartments suffered major damage with 477 others also incurring damage. Twenty six businesses had major damage with 18 others also incurring damage.

The deaths

4 direct deaths are recorded for this tornado, each with what Storm Data knows of it.

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

20 minutes of warning. NWS ILN issued a tornado warning for this county at 08:52 UTC, 20 minutes before the tornado touched down, in force until 09:55 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 General Thunderstorms Risk. The outlook in force was issued at 05:55 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 live radar over the trackEvery 1999 tornado in OhioEvery tornado in Ohio since 1950Warnings in force in Ohio nowThe forecast where you are

8 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.