Tornadoes · United States · Arizona · 2017

EF0 tornado, St David to Fairbank, Arizona, July 29, 2017

From St David to Fairbank, this EF0 tornado ran 0.1 miles across Cochise County on July 29, 2017, touching down at 4:00 PM MST 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
July 29, 2017
Touchdown
4:00 PM MST (23:00 UTC)
Lifted
4:02 PM MST (23:02 UTC)
On the ground
2 minutes
Path length
0.1 miles (0.2 km)
Path width
10 yards (9 m)
Deaths
0
Injuries
0
County
Cochise County
Touchdown point
31.810, -110.200
Lift-off point
31.809, -110.202
Record number
1707291700-01

What the Weather Service recorded

Numerous thunderstorms moved southwest across southeast Arizona. Flash flooding occurred on the west slopes of the Rincon Mountains. Additionally, a brief landspout tornado was reported over open desert in Cochise County.

A brief landspout tornado occurred over open country south of Saint David.

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.

Issued (UTC)ExpiredProductOffice
19:26 UTC22:15 UTCFlood AdvisoryTWC
22:37 UTC01:30 UTCFlood AdvisoryTWC

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 20:00 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.

Tuscon, AZ (KDMA), 12:00Z

11.0 hours before the tornado, 77 km from the path. July 29, 2017.

Skew-T log-pSkew-T log-p diagram, Tuscon, AZ at 12:00Z on 2017-07-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 212 joules per kilogram, CIN -163, lifted condensation level 1399 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, Tuscon, AZ at 12:00Z on 2017-07-29The 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 16 square meters per square second, 0 to 6 km bulk shear 2 knots.1939Sfc1 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
212 J/kg
Mixed-layer CIN
-163 J/kg
Surface CAPE
441 J/kg
Mixed-layer LCL
1399 m above ground
0-6 km bulk shear
2 kt
0-1 km bulk shear
7 kt
0-1 km storm-relative helicity
16 m²/s²
0-3 km storm-relative helicity
-2 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.8 K/km

Open this sounding in Storm Lab

Tuscon, AZ (KDMA), 00:00Z

1.0 hours after it, 77 km from the path. July 30, 2017.

Skew-T log-pSkew-T log-p diagram, Tuscon, AZ at 00:00Z on 2017-07-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 914 joules per kilogram, CIN -48, lifted condensation level 984 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, Tuscon, AZ at 00:00Z on 2017-07-30The 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 37 square meters per square second, 0 to 6 km bulk shear 10 knots.1939Sfc1 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
914 J/kg
Mixed-layer CIN
-48 J/kg
Surface CAPE
2644 J/kg
Mixed-layer LCL
984 m above ground
0-6 km bulk shear
10 kt
0-1 km bulk shear
5 kt
0-1 km storm-relative helicity
37 m²/s²
0-3 km storm-relative helicity
24 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.9 K/km

Open this sounding in Storm Lab

The surface observations

Fort Huachuca/Libby (FHU), 28 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
21:58 UTC74.562.2250° 16 kt1021.7VCTS
22:13 UTC75.260.8260° 14 kt1021VCTS
22:33 UTC73.460.8260° 13 kt1021.7
22:55 UTC73.460.8260° 14 kt1021
22:58 UTC73.261270° 13 kt1021
23:12 UTC73.460.8270° 13 kt191021.7
23:16 UTC71.660.8280° 13 kt1022-RA
23:39 UTC69.864.4310° 7 kt1022.7RA VCTS
23:54 UTC6860.820° 5 kt151022.4-RA VCTS
23:58 UTC67.361.520° 3 kt1022.4-RA VCTS
00:03 UTC6860.80° 0 kt1022-RA
00:09 UTC6862.6230° 8 kt1021.3-RA
00:12 UTC6862.6240° 7 kt1021.3
00:34 UTC69.864.4230° 5 kt1021-RA
00:53 UTC69.864.4200° 4 kt1021.3VCTS
00:58 UTC70.263.70° 0 kt1021.3

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

The radar

The Tucson radar (KEMX), 42 km away, was scanning. The volume nearest the touchdown began at 22:58 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
23:00 UTCTORNADO6 N FairbankCochise, AZDELAYED REPORT--TORNADO. BASED ON PHOTO FROM BROADCAST MEDIA VIA TWITTER AND REVIEW OF RADAR DATA.
23:45 UTCFLASH FLOOD7 Ese Saguaro NationalPima, AZRINCON CREEK AT RINCON GAUGE RECORDED A CREST OF 9.32 FEET. THIS IS THE 4TH HIGHEST ON RECORD FOR THIS SITE.

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

This ground now

The live radar over the trackEvery 2017 tornado in ArizonaEvery tornado in Arizona since 1950Warnings in force in Arizona nowThe forecast where you are

The other tornadoes of July 29, 2017

1 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
July 295:55 PM MDTEF0Sheridan, MT0.110

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.