Tornadoes · United States · South Dakota · 2015

EF0 tornado, Storla, South Dakota, August 9, 2015

This EF0 tornado ran 0.3 miles across Aurora County on August 9, 2015, touching down at 3:35 PM CDT and reaching 50 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 9, 2015
Touchdown
3:35 PM CDT (20:35 UTC)
Lifted
3:36 PM CDT (20:36 UTC)
On the ground
1 minutes
Path length
0.3 miles (0.5 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Aurora County
Touchdown point
43.810, -98.440
Lift-off point
43.807, -98.435
Record number
1508091435-01

What the Weather Service recorded

Widespread severe storms spread from north of Interstate 90 to south during the afternoon and evening of August 9th. Numerous reports of large hail and damaging winds were received, and there was one brief tornado.

A brief tornado, a landspout, caused no reported damage.

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

The warnings

2 minutes of warning. NWS FSD issued a tornado warning for this county at 20:33 UTC, 2 minutes before the tornado touched down, in force until 21:00 UTC.

The county was under a severe thunderstorm watch, issued at 18:45 UTC and running to 23:47 UTC.

Issued (UTC)ExpiredProductOffice
18:45 UTC23:47 UTCSevere Thunderstorm WatchFSD
20:24 UTC21:00 UTCSevere Thunderstorm WarningFSD
20:33 UTC21:00 UTCTornado WarningFSD
20:57 UTC21:30 UTCSevere Thunderstorm WarningFSD

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 20:01 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.

Aberdeen, SD (KABR), 12:00Z

8.6 hours before the tornado, 121 km from the path. August 9, 2015.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 12:00Z on 2015-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 57 joules per kilogram, CIN -195, lifted condensation level 1506 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, Aberdeen, SD at 12:00Z on 2015-08-09The 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 17 square meters per square second, 0 to 6 km bulk shear 35 knots.1939587897Sfc1 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
57 J/kg
Mixed-layer CIN
-195 J/kg
Surface CAPE
147 J/kg
Mixed-layer LCL
1506 m above ground
0-6 km bulk shear
35 kt
0-1 km bulk shear
12 kt
0-1 km storm-relative helicity
17 m²/s²
0-3 km storm-relative helicity
85 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.0 K/km

Open this sounding in Storm Lab

Aberdeen, SD (KABR), 00:00Z

3.4 hours after it, 121 km from the path. August 10, 2015.

Skew-T log-pSkew-T log-p diagram, Aberdeen, SD at 00:00Z on 2015-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 18 joules per kilogram, CIN -139, lifted condensation level 1272 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, Aberdeen, SD at 00:00Z on 2015-08-10The 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 97 square meters per square second, 0 to 6 km bulk shear 37 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
18 J/kg
Mixed-layer CIN
-139 J/kg
Surface CAPE
1345 J/kg
Mixed-layer LCL
1272 m above ground
0-6 km bulk shear
37 kt
0-1 km bulk shear
13 kt
0-1 km storm-relative helicity
97 m²/s²
0-3 km storm-relative helicity
245 m²/s²
Significant tornado parameter
-0.0
Supercell composite
-1.0
0-3 km lapse rate
6.5 K/km

Open this sounding in Storm Lab

The surface observations

Mitchell (MHE), 32 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
18:53 UTC807150° 6 kt1013.9-RA
19:18 UTC807190° 3 kt1013.5VCTS
19:33 UTC807180° 5 kt1013.2
19:44 UTC797280° 3 kt1013.2VCTS
19:53 UTC797290° 4 kt1012.9VCTS
20:06 UTC8371110° 3 kt1012.5
20:53 UTC85700° 0 kt1012.2
21:00 UTC8570 3 kt1012.2VCTS
21:24 UTC8369140° 5 kt1012.5TS
21:49 UTC73.469.8310° 29 kt381013.5+TSRA BR
21:53 UTC6966320° 29 kt411013.9+TSRA FG
21:57 UTC6764300° 30 kt531015.2+TSRA FG
22:04 UTC676660° 17 kt531013.2+TSRA FG
22:09 UTC686790° 9 kt221012.9+TSRA FG
22:15 UTC696850° 12 kt1012.9-TSRA BR
22:19 UTC7068140° 8 kt1012.9-TSRA

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

The radar

The Sioux Falls radar (KFSD), 140 km away, was scanning. The volume nearest the touchdown began at 20:33 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
20:30 UTCHAIL 1.58 W Wessington SpringsJerauld, SD
20:32 UTCHAIL 1.758 Wsw Wessington SpringsJerauld, SD
20:35 UTCTORNADO7 Nne PlankintonAurora, SDLANDSPOUT BRIEFLY TOUCHED DOWN
20:45 UTCTSTM WND DMG8 S Wessington SpringsJerauld, SDTHREE TO FOUR INCH DIAMETER TREES AND LIMBS DOWN
20:50 UTCHAIL 19 Sw Wessington SpringsJerauld, SD
20:52 UTCHAIL 18 S Wessington SpringsJerauld, SD
21:13 UTCHAIL 1.510 Ssw WoonsocketAurora, SDSMOOTH QUARTER TO JAGGED PING PONG
21:53 UTCHAIL 19 Nw Wessington SpringsJerauld, SDCORN SHREDDED BY HAIL AND WIND...TIME ESTIMATED FROM RADAR
21:55 UTCTSTM WND GST 613 N MitchellDavison, SD
22:30 UTCHAIL 11 Ese LaneJerauld, SDTIME ESTIMATED FROM RADAR
22:30 UTCHAIL 1.251 E FultonHanson, SD
22:39 UTCHAIL 1.51 Ssw WoonsocketSanborn, SDSOCIAL MEDIA REPORT...TIME ESTIMATED FROM RADAR
22:42 UTCTSTM WND GST 604 S WoonsocketSanborn, SDTIME ESTIMATED FROM RADAR
23:00 UTCHAIL 13 E EthanHanson, SDSOCIAL MEDIA REPORT

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

This ground now

The live radar over the trackEvery 2015 tornado in South DakotaEvery tornado in South Dakota since 1950Warnings in force in South Dakota nowThe forecast where you are

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.