Tornadoes · United States · Missouri · 2012

EF0 tornado, Saint Charles County, Missouri, August 31, 2012

This EF0 tornado ran 0.4 miles across Saint Charles County on August 31, 2012, touching down at 5:34 PM CDT and reaching 120 yards wide. It killed nobody.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  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.

The record

Rating
EF0
Date
August 31, 2012
Touchdown
5:34 PM CDT (22:34 UTC)
Lifted
5:35 PM CDT (22:35 UTC)
On the ground
1 minutes
Path length
0.4 miles (0.6 km)
Path width
120 yards (110 m)
Deaths
0
Injuries
0
County
Saint Charles County
Touchdown point
38.818, -90.667
Lift-off point
38.823, -90.670
Record number
1208311634-01

The warnings

0 minutes of warning. NWS LSX issued a tornado warning for this county at 22:34 UTC, 0 minutes before the tornado touched down, in force until 22:45 UTC.

The county was under a tornado watch, issued at 18:58 UTC and running to 00:22 UTC.

Issued (UTC)ExpiredProductOffice
18:58 UTC00:22 UTCTornado WatchLSX
19:48 UTC20:05 UTCTornado WarningLSX
22:34 UTC22:45 UTCTornado WarningLSX

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 forecast that day

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 19:58 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 air that afternoon

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.

Lincoln, IL (KILX), 12:00Z

10.6 hours before the tornado, 231 km from the path. August 31, 2012.

Skew-T log-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2012-08-31Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 947 joules per kilogram, CIN -143, lifted condensation level 1049 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Lincoln, IL at 12:00Z on 2012-08-31The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -60 square meters per square second, 0 to 6 km bulk shear 20 knots.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
947 J/kg
Mixed-layer CIN
-143 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1049 m above ground
0-6 km bulk shear
20 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
-60 m²/s²
0-3 km storm-relative helicity
-45 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.3
0-3 km lapse rate
2.7 K/km

Open this sounding in Storm Lab

Lincoln, IL (KILX), 00:00Z

1.4 hours after it, 231 km from the path. September 1, 2012.

Skew-T log-pSkew-T log-p diagram, Lincoln, IL at 00:00Z on 2012-09-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1227 joules per kilogram, CIN -5, lifted condensation level 718 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Lincoln, IL at 00:00Z on 2012-09-01The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 59 square meters per square second, 0 to 6 km bulk shear 28 knots.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
1227 J/kg
Mixed-layer CIN
-5 J/kg
Surface CAPE
922 J/kg
Mixed-layer LCL
718 m above ground
0-6 km bulk shear
28 kt
0-1 km bulk shear
20 kt
0-1 km storm-relative helicity
59 m²/s²
0-3 km storm-relative helicity
52 m²/s²
Significant tornado parameter
0.1
Supercell composite
0.6
0-3 km lapse rate
5.4 K/km

Open this sounding in Storm Lab

The surface observations

St. Louis/Spirit (SUS), 18 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:54 UTC797580° 10 kt1012.9-RA
21:54 UTC797590° 5 kt1011.5RA BR
21:59 UTC78.875.20° 0 kt1011.5+RA BR
22:10 UTC78.875.2220° 10 kt141012.2+RA FG
22:16 UTC7773.4200° 8 kt141012.2RA BR
22:23 UTC78.873.4180° 9 kt161012.2TSRA BR
22:32 UTC7773.4150° 7 kt151012.5RA BR
22:54 UTC7673120° 7 kt1012.5RA BR
23:54 UTC7572110° 6 kt1012.2

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

The radar

The St Louis radar (KLSX), 14 km away, was scanning. The volume nearest the touchdown began at 22:36 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
20:00 UTCHEAVY RAIN 1.336 Ene MarthasvilleSt. Charles, MORAINFALL SINCE 7 AM.
22:31 UTCTORNADO3 Ne O'FallonSt. Charles, MOWOODEN SHED DESTROYED. SOCCER GOAL THROWN INTO TREE LINE. WINDOW BLOWN OUT. ALL DAMAGE AT FORT ZUMWALT NORTH HIGH SCHOOL.
22:32 UTCTORNADO2 Ne O'FallonSt. Charles, MOFEW MEDIUM SIZED TREES UPROOTED. SOCCER POSTS TIPPED THROWN.
22:32 UTCTORNADO3 Ne O'FallonSt. Charles, MOFEW MEDIUM SIZED TREES UPROOTED. SOCCER POSTS TIPPED THROWN AT TR HUGHES HIGHWAY 79.
23:39 UTCFLOODSt. LouisSt. Louis City, MO4-5 INCHES OF STANDING WATER ON SKINKER NEAR FOREST PARK PARKWAY.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2012 tornado in MissouriEvery tornado in Missouri since 1950Warnings in force in Missouri nowThe forecast where you are

The other tornadoes of August 31, 2012

5 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 312:36 PM CDTEF0Jersey, IL0.240
August 312:50 PM CDTEF0Madison, IL0.250
August 313:27 PM CDTEF0Greene, IL1.460
August 315:12 PM CDTEF1Morgan, IL0.3751$230,000
August 315:32 PM CDTEF0Morgan, IL0.210

What this means

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.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.