Tornadoes · United States · Arizona · 2011

EF2 tornado, Flagstaff, Arizona, September 14, 2011

This EF2 tornado ran 0.5 miles across Coconino County on September 14, 2011, touching down at 5:23 PM MST 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 mph

    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 mphthis tornado

    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
EF2
Date
September 14, 2011
Touchdown
5:23 PM MST (00:23 UTC)
Lifted
5:26 PM MST (00:26 UTC)
On the ground
3 minutes
Path length
0.5 miles (0.8 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Coconino County
Touchdown point
35.335, -111.706
Lift-off point
35.335, -111.697
Record number
1109141823-01

What the Weather Service recorded

A low pressure center over northwestern Arizona brought abundant moisture and dynamics to central and eastern parts of northern Arizona. This lead to thunderstorms producing a tornado, large hail, heavy rain, and flash flooding.

A storm survey revealed that significant forest damage occurred along the Humpherys Trail near the Snowbowl Ski Area around 10,000 feet elevation. Preliminary rating was EF2.

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.

Issued (UTC)ExpiredProductOffice
18:57 UTC19:30 UTCSevere Thunderstorm WarningFGZ
19:13 UTC19:45 UTCSevere Thunderstorm WarningFGZ
19:20 UTC19:45 UTCTornado WarningFGZ
19:48 UTC20:15 UTCSevere Thunderstorm WarningFGZ
20:10 UTC20:31 UTCSevere Thunderstorm WarningFGZ
20:12 UTC20:33 UTCSevere Thunderstorm WarningFGZ
20:22 UTC20:45 UTCSevere Thunderstorm WarningFGZ
20:45 UTC21:03 UTCSevere Thunderstorm WarningFGZ
20:55 UTC23:00 UTCFlash Flood WarningFGZ
21:06 UTC21:30 UTCSevere Thunderstorm WarningFGZ
21:06 UTC21:30 UTCSevere Thunderstorm WarningFGZ
21:21 UTC23:45 UTCFlood AdvisoryFGZ
23:22 UTC01:15 UTCFlash Flood WarningFGZ
01:23 UTC04:15 UTCFlood AdvisoryFGZ
04:45 UTC06:30 UTCFlood AdvisoryFGZ
15:59 UTC18:34 UTCFlood AdvisoryFGZ

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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 20:23 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.

Flgstf/Belemont, AZ (KFGZ), 00:00Z

0.4 hours before the tornado, 15 km from the path. September 15, 2011.

Skew-T log-pSkew-T log-p diagram, Flgstf/Belemont, AZ at 00:00Z on 2011-09-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 351 joules per kilogram, CIN -7, lifted condensation level 903 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 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, Flgstf/Belemont, AZ at 00:00Z on 2011-09-15The 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 126 square meters per square second, 0 to 6 km bulk shear 31 knots.193958Sfc1 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
351 J/kg
Mixed-layer CIN
-7 J/kg
Surface CAPE
1098 J/kg
Mixed-layer LCL
903 m above ground
0-6 km bulk shear
31 kt
0-1 km bulk shear
24 kt
0-1 km storm-relative helicity
126 m²/s²
0-3 km storm-relative helicity
174 m²/s²
Significant tornado parameter
0.2
Supercell composite
2.5
0-3 km lapse rate
7.4 K/km

Open this sounding in Storm Lab

Flgstf/Belemont, AZ (KFGZ), 12:00Z

11.6 hours after it, 15 km from the path. September 15, 2011.

Skew-T log-pSkew-T log-p diagram, Flgstf/Belemont, AZ at 12:00Z on 2011-09-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 154 joules per kilogram, CIN -7, lifted condensation level 763 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 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, Flgstf/Belemont, AZ at 12:00Z on 2011-09-15The 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 113 square meters per square second, 0 to 6 km bulk shear 24 knots.193958Sfc1 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
154 J/kg
Mixed-layer CIN
-7 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
763 m above ground
0-6 km bulk shear
24 kt
0-1 km bulk shear
22 kt
0-1 km storm-relative helicity
113 m²/s²
0-3 km storm-relative helicity
160 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.8
0-3 km lapse rate
4.9 K/km

Open this sounding in Storm Lab

The radar

The Flagstaff radar (KFSX), 96 km away, was scanning. The volume nearest the touchdown began at 00:23 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
00:23 UTCTORNADO1 N Arizona SnowbowlCoconino, AZSTORM SURVEY REVEALS SIGNIFICANT FOREST DAMAGE ALONG HUMPHREYS TRAIL NEAR SNOWBOWL NEAR THE 10K FT ELEVATION. PRELIMINARY RATING EF2.

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 ArizonaEvery tornado in Arizona since 1950Warnings in force in Arizona 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.