Tornadoes · United States · South Dakota · 2007

EF0 tornado, St Francis, South Dakota, August 3, 2007

This EF0 tornado ran 0.0 miles across Todd County on August 3, 2007, touching down at 5:30 PM CDT and reaching 10 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 3, 2007
Touchdown
5:30 PM CDT (22:30 UTC)
Path length
0.0 miles (0.0 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
County
Todd County
Touchdown point
42.990, -100.841
Lift-off point
42.990, -100.841
Record number
0708031630-01

What the Weather Service recorded

A tornadic thunderstorm clipped far southern Todd County, producing a tornado southeast of St. Francis. Heavy rain also flooded several county roads in southern Todd County and backed up storm drains in St. Francis.

A deputy sheriff observed a small tornado briefly touch down 12-15 miles west of Highway 83 just north of the Nebraska state line.

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

The warnings

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.

The county was under a tornado watch, issued at 20:21 UTC and running to 01:15 UTC.

Issued (UTC)ExpiredProductOffice
20:21 UTC01:15 UTCTornado WatchLBF
20:23 UTC21:00 UTCTornado WarningLBF
22:24 UTC22:42 UTCSevere Thunderstorm WarningLBF
22:46 UTC23:45 UTCTornado WarningLBF
23:43 UTC00:15 UTCTornado WarningLBF
00:14 UTC00:45 UTCSevere Thunderstorm WarningLBF

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 20:07 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.

Rapid City, SD (KUNR), 12:00Z

10.5 hours before the tornado, 204 km from the path. August 3, 2007.

Skew-T log-pSkew-T log-p diagram, Rapid City, SD at 12:00Z on 2007-08-03Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 70 joules per kilogram, CIN -100, lifted condensation level 1035 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, Rapid City, SD at 12:00Z on 2007-08-03The 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 -12 square meters per square second, 0 to 6 km bulk shear 17 knots.19395878Sfc1 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
70 J/kg
Mixed-layer CIN
-100 J/kg
Surface CAPE
779 J/kg
Mixed-layer LCL
1035 m above ground
0-6 km bulk shear
17 kt
0-1 km bulk shear
6 kt
0-1 km storm-relative helicity
-12 m²/s²
0-3 km storm-relative helicity
83 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0
0-3 km lapse rate
5.5 K/km

Open this sounding in Storm Lab

Rapid City, SD (KUNR), 00:00Z

1.5 hours after it, 204 km from the path. August 4, 2007.

Skew-T log-pSkew-T log-p diagram, Rapid City, SD at 00:00Z on 2007-08-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1506 joules per kilogram, CIN -27, lifted condensation level 1382 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, Rapid City, SD at 00:00Z on 2007-08-04The 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 26 square meters per square second, 0 to 6 km bulk shear 34 knots.19395878Sfc1 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
1506 J/kg
Mixed-layer CIN
-27 J/kg
Surface CAPE
1879 J/kg
Mixed-layer LCL
1382 m above ground
0-6 km bulk shear
34 kt
0-1 km bulk shear
8 kt
0-1 km storm-relative helicity
26 m²/s²
0-3 km storm-relative helicity
80 m²/s²
Significant tornado parameter
0.2
Supercell composite
2.0
0-3 km lapse rate
7.2 K/km

Open this sounding in Storm Lab

The surface observations

Valentine (VTN), 28 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:52 UTC8068160° 14 kt1014.2
21:52 UTC8266180° 20 kt251013.5
22:08 UTC80.666.2170° 12 kt191012.9TS
22:52 UTC8166160° 15 kt201011.9TS
23:50 UTC75.266.2350° 10 kt201012.5TS
23:52 UTC7367350° 9 kt201012.2TS
00:28 UTC73.468330° 9 kt1013.2+TSRA

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

The radar

The North Platte radar (KLNX), 117 km away, was scanning. The volume nearest the touchdown began at 22:30 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
22:07 UTCFUNNEL CLOUD1 Se Spring CreekTodd, SDSPOTTERS REPORTED FUNNEL CLOUD 1.5 MILES SOUTHEAST OF SPRING CREEK AREA.
22:34 UTCTORNADO11 Se Saint FrancisTodd, SDSPOTTERS REPORTED TORNADO ON THE GROUND WITH VISIBLE DEBREE CLOUD.
23:00 UTCFLOOD16 S MissionTodd, SDWATER FLOODING OVER COUNTY ROAD 105 16 MILES SOUTH OF MISSION.
23:15 UTCFLOOD2 S Saint FrancisTodd, SDCOUNTY ROAD 504 2 MILES SOUTH OF SAINT FRANCIS WASHED OUT.
23:15 UTCFLOODSaint FrancisTodd, SDSTORM DRAINS BACKED UP IN TOWN.
23:27 UTCFUNNEL CLOUD9 N ValentineTodd, SDSEVERAL FUNNEL CLOUDS REPORTED.

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

This ground now

The live radar over the trackEvery 2007 tornado in South DakotaEvery tornado in South Dakota since 1950Warnings in force in South Dakota nowThe forecast where you are

The other tornadoes of August 3, 2007

2 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 36:02 PM MDTEF0Cherry, NE0.110
August 38:30 PM CDTEF0Wheeler, NE0.110

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.