Tornadoes · United States · Montana · 2015

EF0 tornado, Willard, Montana, June 21, 2015

This EF0 tornado ran 1.0 miles across Fallon County on June 21, 2015, touching down at 4:37 PM MDT 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
June 21, 2015
Touchdown
4:37 PM MDT (22:37 UTC)
Lifted
4:42 PM MDT (22:42 UTC)
On the ground
5 minutes
Path length
1.0 miles (1.6 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Fallon County
Touchdown point
46.220, -104.400
Lift-off point
46.220, -104.400
Record number
1506211637-01

What the Weather Service recorded

A strong upper level wave moved across Eastern Montana during the afternoon and evening hours of the 16th. An axis of instability combined with strong and low, deep layer shear and high dewpoints resulted in a very unstable environment. This resulted in several supercell thunderstorms that produced large hail, damaging winds and one confirmed tornado across the eastern portions of the Billings Forecast Area.

A weak tornado was reported between Baker and Ekalaka during the late afternoon hours on the 21st. The tornado was on the ground for around a minute. It began roping out about 4 minutes later and its circulation appeared to fully cut off around 90 seconds after that.

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.

The county was under a tornado watch, issued at 20:24 UTC and running to 04:00 UTC.

Issued (UTC)ExpiredProductOffice
20:24 UTC04:00 UTCTornado WatchBYZ
21:47 UTC22:45 UTCSevere Thunderstorm WarningBYZ
22:31 UTC23:30 UTCSevere Thunderstorm WarningBYZ
02:22 UTC03:15 UTCSevere Thunderstorm WarningBYZ
03:13 UTC04:15 UTCSevere Thunderstorm WarningBYZ

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 20:02 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 (KRAP), 12:00Z

10.6 hours before the tornado, 267 km from the path. June 21, 2015.

Skew-T log-pSkew-T log-p diagram, Rapid City, SD at 12:00Z on 2015-06-21Temperature 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 -87059, lifted condensation level 1334 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, Rapid City, SD at 12:00Z on 2015-06-21The 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 -57 square meters per square second, 0 to 6 km bulk shear 51 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
0 J/kg
Mixed-layer CIN
-87059 J/kg
Surface CAPE
2 J/kg
Mixed-layer LCL
1334 m above ground
0-6 km bulk shear
51 kt
0-1 km bulk shear
7 kt
0-1 km storm-relative helicity
-57 m²/s²
0-3 km storm-relative helicity
-69 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

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

1.4 hours after it, 267 km from the path. June 22, 2015.

Skew-T log-pSkew-T log-p diagram, Rapid City, SD at 00:00Z on 2015-06-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1709 joules per kilogram, CIN -112, lifted condensation level 1661 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 2015-06-22The 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 189 square meters per square second, 0 to 6 km bulk shear 59 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
1709 J/kg
Mixed-layer CIN
-112 J/kg
Surface CAPE
3059 J/kg
Mixed-layer LCL
1661 m above ground
0-6 km bulk shear
59 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
189 m²/s²
0-3 km storm-relative helicity
236 m²/s²
Significant tornado parameter
0.5
Supercell composite
12.2
0-3 km lapse rate
6.8 K/km

Open this sounding in Storm Lab

What was reported nearby

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

Time (UTC)ReportWhereCountyRemark
21:45 UTCHAIL 1.756 W IsmayCuster, MTSPOTTER REPORTED HAIL UP TO THE SIZE OF GOLF BALLS. WITH WINDOWS KNOCKED OUT OF HOUSE.
21:55 UTCHAIL 2.757 Ssw IsmayCuster, MTSPOTTER REPORTED BASEBALL HAIL THAT DESTROYED THEIR WINDSHIELD AND WIND GUST OF 70 MPH.
21:55 UTCNON-TSTM WND GST 707 Ssw IsmayCuster, MTSPOTTER REPORTED BASEBALL HAIL THAT DESTROYED THEIR WINDSHIELD AND WIND GUST OF 70 MPH.
22:00 UTCHAIL 2.55 S IsmayFallon, MTGOLF BALL TO TENNIS BALL SIZED HAIL 3 TO 4 INCH DEEP ALONG ROAD. TREES COMPLETELY BARE...LIKE WINTER TIME. ROADSIDE REFLECTORS SHATTERED ALL ALONG HWY 12 MM55.
22:40 UTCHAIL 1.751 Nne WillardFallon, MTSPOTTER REPORTED GOLFBALL HAIL.

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 MontanaEvery tornado in Montana since 1950Warnings in force in Montana nowThe forecast where you are

The other tornadoes of June 21, 2015

6 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 216:50 PM MDTEF0Perkins, SD5.150
June 217:10 PM MDTEF0Perkins, SD2.020
June 217:40 PM MDTEF0Perkins, SD3.0100
June 217:56 PM MDTEF0Perkins, SD0.040
June 218:05 PM MDTEF0Perkins, SD2.620
June 218:50 PM MDTEF0Ziebach, SD1.610

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.