On the afternoon of October 10, thunderstorms developed over the ridge tops of Monterey and San Benito Counties. The storms produced frequent lightning and heavy downpours.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MTR wrote it up.
On the afternoon of October 10, thunderstorms developed over the ridge tops of Monterey and San Benito Counties. The storms produced frequent lightning and heavy downpours. A heavy thunderstorm developed near Hollister California and moved west northwest through the southern Santa Clara Valley. The storm briefly became severe near the town of Gilroy and produced large hail and torrential downpours. The storm continued moving west and dissipated in the Santa Cruz Mountains.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Oct 10, 12:58 PM PST, 1 hour 42 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
158 PM PDT WED OCT 10 2012
.DISCUSSION...AS OF 2:00 PM PDT WEDNESDAY...BAY AREA RADARS HAVE
PICKED UP SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THE
DAY TODAY AS A STORM SYSTEM CONTINUES TO ROTATE OFF OF THE
CALIFORNIA COAST. RAINFALL AMOUNTS HAVEN'T BEEN IMPRESSIVE BUT IT
IS INTERESTING TO NOTE THAT MOST OF THE RAIN FELL IN THE MIDDLE
THIRD OF THE CWA -- INSTEAD OF THE NORTHERN OR SOUTHERN PORTIONS
WHICH TENDS TO BE MORE COMMON. WE DID GET ONE REPORT FROM FAR
SOUTHWESTERN MONTEREY COUNTY OF AROUND A THIRD OF AN INCH FROM A
STRONG CELL THAT WENT OVER EARLIER. AT THIS TIME THAT IS THE
HIGHEST AMOUNT DETECTED.
EXPECT A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN
HALF OF THE CWA THROUGH TONIGHT AS THE LOW SLOWLY PROGRESSES TO
THE SOUTHEAST WHILE THE ATMOSPHERE REMAINS MODERATELY UNSTABLE. AS
THE NIGHT PROGRESSES LIFTED VALUES WILL FLIP BACK TO POSITIVE
NUMBERS HELPING TO GREATLY REDUCE THE RISK OF CONVECTION. ANY
ADDITIONAL RAINFALL SHOULD BE ON THE LIGHT SIDE WITH THE EXCEPTION
OF A BRIEF LOCAL DOWNPOUR DUE TO A STRONGER CELL. IN GENERAL LESS
THAN A TENTH OF AN INCH IS ANTICIPATED.
THE LOW WILL MOVE ONSHORE OVER SOUTHERN CALIFORNIA ON THURSDAY AND
PROGRESS TO NEAR THE FOUR CORNERS ON FRIDAY. BEHIND IT TEMPERATES
WILL START TO WARM AS 500 MB HEIGHTS BUILD BACK TO AROUND 580 DM
ON FRIDAY COMPARED TO 562 TODAY AND THEN UP TO 586 DM OVER THE WEEKEND.
THIS COMBINED WITH INCREASING AMOUNTS OF SUNSHINE WILL HELP TO
BOOST HIGHS BACK INTO THE 70S FOR MANY INTERIOR SPOTS OVER THE
WEEKEND WITH MID 60S TO LOWER 70S AT THE COAST. SOME 80S ARE
DEFINITELY POSSIBLE ON SUNDAY.
LONGER RANGE MODELS BRING A REX BLOCK BACK TO NEAR OUR CWA FOR
NEXT WEEK WITH THE STORM TRACK WELL TO OUR NORTH. HIGHS SHOULD
BE ABOVE NORMAL NEXT WEEK AND COULD APPROACH WELL ABOVE NORMAL
VALUES BY WEDNESDAY. IN FACT...IF THE ECMWFBC VERIFIES WE COULD
SEE 90S BACK IN THE NORTH BAY. DIDN'T FEEL CONFIDENT ENOUGH TO GO
THAT HIGH THAT FAR OUT...BUT IT IS WORTH MENTIONING
&&
.AVIATION...AS OF 10:45 AM WEDNESDAY...MAIN BANDS OF SHOWERS AND
CLOUDS FROM THE UPPER LOW THIS MORNING HAVE MOVED SOUTH AT THIS
HOUR. LOW CLOUDS IN SF BAY ARE RAPIDLY CLEARING AND ALL TERMINALS
SHOULD RETURN TO VFR BY NOON. LIGHT WINDS TODAY. AN ISOLATED
SHOWER OR TWO IS STILL POSSIBLE THIS AFTERNOON. STRATUS POSSIBLE
TONIGHT...LOW CONFIDENCE.
.VICINITY OF KSFO...LOW CIGS TO SCATTER WITHIN THE NEXT HOUR. WEST
WINDS MOSTLY LESS THAN 10 KT. LOW CIGS POSSIBLE AGAIN TONIGHT.
KSFO BRIDGE APPROACH...SIMILAR TO KSFO.
MONTEREY BAY AREA TERMINALS...VFR. LIGHT WINDS.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.TNGT...NONE.
PUBLIC FORECAST: BELL
AVIATION/MARINE: AC
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WWW.TWITTER.COM/NWSBAYAREAThe San Francisco radar (KMUX), 31 km away, was scanning. The volume nearest the first event began at 22:39 UTC.
2 hail. Local standard time, as filed.
At 3:40 PM an employee of the Santa Clara County OES observed a severe thunderstorm that produced large hail at his home. He measured hail from dime to quarter size that produced minor damage to plants around his home.
Spotters from the town of Gilroy in Santa Clara County reported that pea sized hail fell during a severe thunderstorm in the area. Hail accumulated up to depths of 2 inches across the area. Minor damage to vegetable plants was observed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2012Every state in 2012This day in weather historyWarnings in California, October 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 419269, 419270.