EF0 tornado, Henleyville, California, January 4, 2021

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.

Rating

EF0

Date

January 4, 2021

Touchdown

1:34 PM PST (21:34 UTC)

Lifted

1:39 PM PST (21:39 UTC)

On the ground

5 minutes

Path length

0.8 miles (1.3 km)

Path width

3 yards (3 m)

Deaths

0

Injuries

0

County

Tehama County

Touchdown point

39.960, -122.330

Lift-off point

39.949, -122.334

Record number

2101041534-01

A trough from the Gulf of Alaska brought Valley rain, mountain snow, and thunderstorms to northern California. The system hit in two waves, the initial frontal passage followed the trough axis moving over northern California. Clearing behind the cold front allowed for a favorable thunderstorm environment to develop, which would eventually lead to two confirmed tornadoes for interior northern California. Snow levels with this system started around 5,000 and 6,500 feet and dropped down to 4,000 and 4,500 feet.

A possible tornado touchdown was reported by a member of the public in western Corning, with multiple trees knocked down, a barn and other buildings damaged, and a power pole knocked down. Calfire dispatched to the area for power line damage also observed downed trees around the intersection of Apple Rd and Simpson Rd. Tornado track, width, and timing estimated by radar and storm reports.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

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.

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 Storm Prediction Center had this point in a Marginal Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 19:35 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 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.

Red Bluff Municipal (RBL), 23 km from the path, in the two hours either side.

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

The Beale AFB radar (KBBX), 79 km away, was scanning. The volume nearest the touchdown began at 21:36 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.

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

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

The live radar over the trackEvery 2021 tornado in CaliforniaEvery tornado in California since 1950Warnings in force in California nowThe forecast where you are

1 more were confirmed in the United States that day.

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.