Tornadoes · United States · California · 2015

EF1 tornado, Mecca to (Trm)Thermal Arpt, California, August 6, 2015

From Mecca to (Trm)Thermal Arpt, this EF1 tornado ran 4.0 miles across Riverside County on August 6, 2015, touching down at 8:15 PM PDT and reaching 900 yards wide. It killed nobody and injured 2, and did $18 million of property damage.

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 mphthis tornado

    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
EF1
Date
August 6, 2015
Touchdown
8:15 PM PDT (03:15 UTC)
Lifted
8:45 PM PDT (03:45 UTC)
On the ground
30 minutes
Path length
4.0 miles (6.4 km)
Path width
900 yards (823 m)
Deaths
0
Injuries
2
Property damage
$18 million
County
Riverside County
Touchdown point
33.565, -116.108
Lift-off point
33.600, -116.152
Record number
1508062115-01

What the Weather Service recorded

Monsoon moisture and some instability from an easterly wave resulted in scattered thunderstorms over the mountains and lower deserts. Most notable of these was a severe thunderstorm that occurred near Mecca in the southern Coachella Valley during the evening. This storm produced a copious amount of lightning and very strong, damaging winds (over 100 power poles damaged or destroyed). While the precipitation did not hit many gages, the Kent Sea Farms gage, near Mecca, recorded 0.32 inches of rain with this storm. After storm damage surveys, it was concluded that the most likely cause of the damage was a brief, nearly-stationary, EF1 tornado.

The damage was west of Highway 111 between 64th and 66th Avenues, paralleling Highway 86 towards the mountains, or approximately 3 1/2 miles. An emergency manager for the Imperial irrigation water district (IID) reported a total of 140 poles damaged, 30 of which were steel.

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
21:47 UTC22:15 UTCSevere Thunderstorm WarningPSR
22:14 UTC22:30 UTCSevere Thunderstorm WarningPSR
22:57 UTC02:00 UTCFlood AdvisoryPSR
02:26 UTC02:45 UTCSevere Thunderstorm WarningPSR
02:38 UTC03:30 UTCSevere Thunderstorm WarningSGX
03:18 UTC04:00 UTCSevere Thunderstorm WarningSGX
04:27 UTC05:00 UTCSevere Thunderstorm WarningPSR
07:46 UTC09:13 UTCFlood AdvisoryPSR

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 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.

San Diego, CA (KNKX), 00:00Z

3.3 hours before the tornado, 132 km from the path. August 7, 2015.

Skew-T log-pSkew-T log-p diagram, San Diego, CA at 00:00Z on 2015-08-07Temperature 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 -83758, lifted condensation level 2253 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, San Diego, CA at 00:00Z on 2015-08-07The 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 18 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
0 J/kg
Mixed-layer CIN
-83758 J/kg
Surface CAPE
7 J/kg
Mixed-layer LCL
2253 m above ground
0-6 km bulk shear
31 kt
0-1 km bulk shear
4 kt
0-1 km storm-relative helicity
18 m²/s²
0-3 km storm-relative helicity
101 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.4 K/km

Open this sounding in Storm Lab

San Diego, CA (KNKX), 12:00Z

8.7 hours after it, 132 km from the path. August 7, 2015.

Skew-T log-pSkew-T log-p diagram, San Diego, CA at 12:00Z on 2015-08-07Temperature 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 -61816, lifted condensation level 1153 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, San Diego, CA at 12:00Z on 2015-08-07The 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 1 square meters per square second, 0 to 6 km bulk shear 29 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
-61816 J/kg
Surface CAPE
10 J/kg
Mixed-layer LCL
1153 m above ground
0-6 km bulk shear
29 kt
0-1 km bulk shear
6 kt
0-1 km storm-relative helicity
1 m²/s²
0-3 km storm-relative helicity
42 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
2.6 K/km

Open this sounding in Storm Lab

The surface observations

Thermal Airport (TRM), 6 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
01:52 UTC10659200° 5 kt1003
02:52 UTC10254 6 kt1003.4

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

The radar

The San Diego radar (KNKX), 112 km away, was scanning. The volume nearest the touchdown began at 03:14 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
03:00 UTCTSTM WND DMG1 Wsw MeccaRiverside, CASURVEY OF DAMAGE AREA BY NWS SHOWS NEAR 2 MILES OF STEEL POWER POLES DAMAGED. 1 MILE OF WOODEN POLES DAMAGED. THIS IS ALONG HIGHWAY 86 BETWEEN AVENUE 64 AND 68. TIME RANGE OF DAMAGE IS ESTIMATED 745 TO 800 PM.
03:00 UTCTSTM WND DMG3 Sw MeccaRiverside, CAMULTIPLE INJURIES AT A MOBILE HOME PARK WHERE SEVERAL OUTDOOR WORKERS WERE TOSSED BY THE WIND. ELSEWHERE IN THE THERMAL AREA, 15 POWERPOLES DOWNED (EXACT LOCATION UNKNOWN AT THIS TIME), VEHICLE STRUCK BY FALLING POWERPOL
03:12 UTCTSTM WND DMG4 Sw MeccaRiverside, CAPOWER POLE FELL ONTO VEHICLE NEAR 70TH AND PIERCE STREETS.
03:15 UTCTSTM WND DMG6 Ssw MeccaRiverside, CA2 LARGE PALM TREES FELL ONTO THE ROAD AT 77TH AND HARRISON. TIME IS APPROXIMATE.

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 CaliforniaEvery tornado in California since 1950Warnings in force in California nowThe forecast where you are

The other tornadoes of August 6, 2015

10 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 64:05 PM CDTEF0Swift, MN0.115
August 64:09 PM CDTEF0Swift, MN0.115
August 64:59 PM CDTEF0Kandiyohi, MN0.125
August 65:03 PM CDTEF0Kandiyohi, MN0.125
August 65:21 PM CDTEF1Yellow Medicine, MN1.9440$500,000
August 66:07 PM CDTEF0Kandiyohi, MN0.625
August 66:33 PM CDTEF0Brookings, SD0.650
August 67:00 PM CDTEF0Brookings, SD0.850$80,000
August 68:40 PM CDTEF0Russell, AL1.9250
August 610:35 PM CDTEF1Pike, AL0.4507

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.