Tornadoes · United States · Idaho · 2011

EF0 tornado, Twin Falls, Idaho, March 16, 2011

This EF0 tornado ran 7.4 miles across Twin Falls County on March 16, 2011, touching down at 4:00 PM MDT 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
March 16, 2011
Touchdown
4:00 PM MDT (22:00 UTC)
Lifted
4:10 PM MDT (22:10 UTC)
On the ground
10 minutes
Path length
7.4 miles (11.8 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
County
Twin Falls County
Touchdown point
42.570, -114.666
Lift-off point
42.621, -114.540
Record number
1103161600-01

What the Weather Service recorded

A strong cold front passing through Southwest Idaho kicked off thunderstorms that spawned a brief tornado near Jerome, Idaho. Damaging winds were also reported near Hollister and Filer.

Local law enforcement officials and the public reported a brief touchdown of a tornado near Filer. A trained spotter in Hollister reported a measured wind gust of 61 MPH and a 30 by 40 foot metal building was blown over near Filer.

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.

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 General Thunderstorms Risk. The outlook in force was issued at 19:39 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.

Boise Airport, ID (KBOI), 12:00Z

10.0 hours before the tornado, 169 km from the path. March 16, 2011.

Skew-T log-pSkew-T log-p diagram, Boise Airport, ID at 12:00Z on 2011-03-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -67261, lifted condensation level 941 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Boise Airport, ID at 12:00Z on 2011-03-16The 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 -136 square meters per square second, 0 to 6 km bulk shear 92 knots.1939587897117136Sfc1 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
0 J/kg
Mixed-layer CIN
-67261 J/kg
Surface CAPE
3 J/kg
Mixed-layer LCL
941 m above ground
0-6 km bulk shear
92 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
-136 m²/s²
0-3 km storm-relative helicity
79 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
6.2 K/km

Open this sounding in Storm Lab

Boise Airport, ID (KBOI), 00:00Z

2.0 hours after it, 169 km from the path. March 17, 2011.

Skew-T log-pSkew-T log-p diagram, Boise Airport, ID at 00:00Z on 2011-03-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -93205, lifted condensation level 981 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Boise Airport, ID at 00:00Z on 2011-03-17The 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 34 square meters per square second, 0 to 6 km bulk shear 53 knots.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
-93205 J/kg
Surface CAPE
68 J/kg
Mixed-layer LCL
981 m above ground
0-6 km bulk shear
53 kt
0-1 km bulk shear
34 kt
0-1 km storm-relative helicity
34 m²/s²
0-3 km storm-relative helicity
22 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
7.4 K/km

Open this sounding in Storm Lab

The surface observations

Twin Falls/Joslin (TWF), 16 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:53 UTC5038210° 21 kt291007.8
21:15 UTC39.233.8260° 36 kt481008.8+RA SQ
21:17 UTC37.433.8260° 37 kt481009.1+RA BR SQ
21:25 UTC37.433.8260° 32 kt451009.5RA BR
21:29 UTC37.433.8250° 25 kt391009.1RA BR
21:33 UTC37.435.6250° 27 kt371009.5-RA BR
21:41 UTC39.235.6250° 26 kt321009.5-RA
21:48 UTC4137.4240° 21 kt311009.5
21:53 UTC4338240° 19 kt281009.5
22:20 UTC39.235.6260° 28 kt451010.2-RA
22:49 UTC4133.8250° 27 kt391010.8
22:53 UTC4232250° 22 kt391011.2
23:24 UTC39.233.8270° 24 kt321012.2-RA
23:36 UTC35.633.8280° 28 kt331012.9-SN BR

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

The radar

The Boise radar (KCBX), 166 km away, was scanning. The volume nearest the touchdown began at 21:59 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
21:15 UTCNON-TSTM WND GST 61HollisterTwin Falls, ID
21:15 UTCNON-TSTM WND DMGFilerTwin Falls, ID30 FOOT BY 40 FOOT METAL BUILDING BLOWN OVER.

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

This ground now

The live radar over the trackEvery 2011 tornado in IdahoEvery tornado in Idaho since 1950Warnings in force in Idaho 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.