Tornadoes · United States · California · 1996

F1 tornado, Tomales, California, December 23, 1996

This F1 tornado ran 6.0 miles across Marin County on December 23, 1996, touching down at 10:00 AM PST and reaching 20 yards wide. It killed nobody, and did $200,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. F040 to 72 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. F173 to 112 mphthis tornado

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. F2113 to 157 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. F3158 to 206 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. F4207 to 260 mph

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. F5261 to 318 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
F1
Date
December 23, 1996
Touchdown
10:00 AM PST (18:00 UTC)
Path length
6.0 miles (9.7 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
Property damage
$200,000
County
Marin County
Touchdown point
38.250, -122.930
Lift-off point
38.250, -122.830
Record number
1084

What the Weather Service recorded

This storm began over the ocean as a water spout that moved in land. It distroyed a large barn and 1o large eucalytus trees, and 5 telephone poles. It also ripped the roof off another house. Afarmer was in the barn when it was blown over but he was not injured. At least two other waterspouts were reported as well as heavy rain and small hail in the tomales bay area.

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.

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.

Oakland, CA (KOAK), 12:00Z

6.0 hours before the tornado, 83 km from the path. December 23, 1996.

Skew-T log-pSkew-T log-p diagram, Oakland, CA at 12:00Z on 1996-12-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 23 joules per kilogram, CIN -15, lifted condensation level 673 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, Oakland, CA at 12:00Z on 1996-12-23The 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 175 square meters per square second, 0 to 6 km bulk shear 74 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
23 J/kg
Mixed-layer CIN
-15 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
673 m above ground
0-6 km bulk shear
74 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
175 m²/s²
0-3 km storm-relative helicity
257 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.1 K/km

Open this sounding in Storm Lab

Oakland, CA (KOAK), 00:00Z

6.0 hours after it, 83 km from the path. December 24, 1996.

Skew-T log-pSkew-T log-p diagram, Oakland, CA at 00:00Z on 1996-12-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 5 joules per kilogram, CIN -19, lifted condensation level 1321 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, Oakland, CA at 00:00Z on 1996-12-24The 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 -34 square meters per square second, 0 to 6 km bulk shear 35 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
5 J/kg
Mixed-layer CIN
-19 J/kg
Surface CAPE
52 J/kg
Mixed-layer LCL
1321 m above ground
0-6 km bulk shear
35 kt
0-1 km bulk shear
7 kt
0-1 km storm-relative helicity
-34 m²/s²
0-3 km storm-relative helicity
97 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.6 K/km

Open this sounding in Storm Lab

The surface observations

Santa Rosa (STS), 29 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
16:00 UTC42.842.80° 0 kt1027.1BR
16:45 UTC44.644.6330° 5 kt1028.1FG
17:00 UTC0° 0 ktBR
17:30 UTC46.446.4320° 7 kt1028.4FZFG
17:45 UTC51.839.2320° 7 kt1028.8
18:47 UTC5048.20° 0 kt1029.8BR
19:30 UTC51.848.2320° 5 kt1029.5BR
19:45 UTC51.848.2320° 5 kt1029.5BR

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

This ground now

The live radar over the trackEvery 1996 tornado in CaliforniaEvery tornado in California since 1950Warnings in force in California nowThe forecast where you are

The other tornadoes of December 23, 1996

4 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
December 2310:45 AM CSTF0Crawford, MO0.550
December 2311:30 AM CSTF0Texas, MO1.050
December 2311:30 AM PSTF0Sonoma, CA0.3201$1,000
December 232:55 PM CSTF1Randolph, IL2.070

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.