EF0 tornado, Merced Arpt, California, February 9, 2009

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

February 9, 2009

Touchdown

11:32 AM PST (19:32 UTC)

Lifted

11:34 AM PST (19:34 UTC)

On the ground

2 minutes

Path length

0.1 miles (0.2 km)

Path width

20 yards (18 m)

Deaths

0

Injuries

0

County

Merced County

Touchdown point

37.210, -120.600

Lift-off point

37.210, -120.600

Record number

0902091332-01

An upper-level low pressure system moved into California on February 6th, heralding a change in the pattern to wetter than normal for the rest of the month. This was the first in a series of systems that would move through the state over the coming week. Bakersfield received a record rainfall of 0.73 inch on the 7th, nearly twice the old record of 0.41 inch (1993). Heavy snowfall occurred in the Sierra Nevada from Yosemite to Sequoia. Reports of snowfall topped over one foot in some portions of the high country on the 6th. A very cold airmass settled over interior California on the 8th, dropping snow levels into the Sierra Nevada foothills and setting the stage for an active weather day on the 9th.||The second, and stronger, upper-level trough moved into central California during the morning of February 9th. Snow levels plummeted during the morning, with snow falling on the San Joaquin Valley floor in western Kern County. Snow fell as far into the Valley as Maricopa, ad an inch of snow fell on Taft. Grocer Grade through the Temblors was closed due to snow, and a Winter Weather Advisory was issued for the southwestern San Joaquin Valley. Snow also fell on the Kern County desert floor near Rosamond. Additional snowfall of one foot or more occurred on the 8th and 9th with the second wave of precipitation across the high mountains of the Sierra Nevada. Snow accumulations of 2 to 4 inches also occurred in the Sierra Foothills between 2000 to 4000 feet. ||Thunderstorms developed over the central San Joaquin Valley by late morning. Funnel clouds were reported over Merced County at 11:20 AM PST, heralding the start of a 25-minute outbreak that saw at least 4, and probably 5, separate funnels. (Media, public and law-enforcement reports included some multiple sightings of the same funnel clouds, leading to the uncertainty in the number.) These funnel clouds developed from just south of Atwater to 14 miles southeast of the city of Merced. At 11:32 AM PST, the Oakland FAA Flight Service Office called with a report from a pilot over Merced County who had just observed one of the funnels briefly touch down in an open field 10 miles south of Castle Airport. Because of the brevity of the touchdown (only a few seconds) and fortunate lack of damage, this tornado was likely an EF-0 on the enhanced Fujita scale. This was the first tornado to touch down in the central/southern San Joaquin Valley (and the entire Hanford Warning/Forecast Area) since the Visalia tornado on January 27th, 2008. The last tornado to occur in Merced County was on March 28th, 2006.||After the trough moved east of California, the very cold airmass remained over the San Joaquin Valley, bringing frost to the area on the morning of February 10th. Subsequent troughs moved into California on the 11th, 13th and 15th, as short-wave impulses rotated around an upper-level low off the northern California coast.

The Federal Aviation Administration office located in Oakland, CA, relayed a pilot report of a brief touchdown of a tornado 10 miles south of Merced Castle Airport. The tornado only last for a couple minutes and caused no property damage. The tornado was rated EF0. The pilot reported the tornado quickly lifted and dissipated. At the time of the report, the funnel had lifted and was dissipating. The touchdown occurred during a period of several funnel cloud reports over an area from Atwater to southeast of Merced Municipal Airport (KMCE).

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.

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 General Thunderstorms Risk. The outlook in force was issued at 16:29 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.

The San Francisco radar (KMUX), 115 km away, was scanning. The volume nearest the touchdown began at 19:33 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 2009 tornado in CaliforniaEvery tornado in California since 1950Warnings in force in California nowThe forecast where you are

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.