EF0 tornado in Merced County, California

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).

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.