On December 29-30, two upper level storm system combined to create a cold, unstable air mass. This produced scattered thunderstorms, locally heavy rain, a few inland funnel clouds, as well as waterspouts over the San Diego County coastal waters.
Every event with a place to put it. Tap one for its entry below.
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 SGX wrote it up.
On December 29-30, two upper level storm system combined to create a cold, unstable air mass. This produced scattered thunderstorms, locally heavy rain, a few inland funnel clouds, as well as waterspouts over the San Diego County coastal waters. The waterspout near Oceanside was observed on the 29th.
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 Diego, CA wrote its last area forecast discussion before the first event at Dec 29, 9:00 AM PST, 30 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
900 AM PST SAT DEC 29 2012
.SYNOPSIS...
INCREASING CLOUDS AND COOLER WITH LIGHT RAIN AND MOUNTAIN SNOW LIKELY
OVER AND WEST OF THE MOUNTAINS TODAY THROUGH SUNDAY AS A COLD
FRONT MOVES THROUGH THE REGION. ISOLATED THUNDERSTORMS ARE ALSO
POSSIBLE THROUGH SUNDAY AFTERNOON. GUSTY WEST WINDS WILL DEVELOP
OVER THE MOUNTAINS AND DESERTS FOR LATE SUNDAY. WEAK TO MODERATE
OFFSHORE FLOW...FAIR WEATHER AND GRADUAL WARMING TUESDAY THROUGH
MOST OF NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS MORNING...SATELLITE IMAGERY SHOWS A LOW PRESSURE SYSTEM
MOVING SOUTHEAST ALONG THE CENTRAL CALIFORNIA COAST. RADAR SHOWS
MOSTLY LIGHT SHOWERS CURRENTLY MOVING THROUGH LOS ANGELES AND
NORTHERN ORANGE COUNTIES...WITH EMBEDDED ISOLATED TSTMS OVER L.A.
COUNTY. POST-FRONTAL CONVECTION CONTINUE TO MOVE INLAND FARTHER TO
THE NORTH. TIMING OF THE PRECIP FOR EXTREME SOUTHWESTERN CA
REMAINS ON TRACK...WITH SHOWERS MOVING INTO SOUTHWEST SAN
BERNARDINO COUNTY LATER THIS MORNING AND SPREADING SOUTH AND EAST
THROUGH THE AFTERNOON. THE BULK OF THE PRECIPITATION IS EXPECTED
TO FALL LATE THIS AFTERNOON AND EVENING AS THE FRONT MOVES
THROUGH...TAPERING OFF TO SHOWERS TONIGHT. SHOWERS MAY LINGER
SUNDAY INTO EARLY MONDAY AS A SECOND SHORTWAVE TROUGH MOVES DOWN
THE BACK SIDE OF THE TROUGH AND OVER SOUTHERN CA. COLD AIR ALOFT
AND MARGINALLY UNSTABLE CONDITIONS COULD CONTINUE ISOLATED
THUNDERSTORMS DURING THE DAY SUNDAY AS WELL.
NUMERICAL MODELS ARE IN GENERALLY GOOD AGREEMENT ON THE TRACK AND
TIMING OF THIS SYSTEM BUT DIFFER SOMEWHAT IN THE DETAILS...WITH
THE GFS AND NAM MODELS HAVING THE DRIER SOLUTIONS. THE PRECIP
FORECAST IS BASED ON A BLEND OF THE ECM AND SREF. RAINFALL TOTALS
FOR THIS SYSTEM WILL RANGE FROM AROUND ONE TENTH TO ONE THIRD INCH
IN THE COASTS/VALLEYS AND ONE QUARTER TO ONE HALF INCH IN THE
MOUNTAINS. LOCALLY HIGHER AMOUNTS ARE POSSIBLE IN HEAVIER SHOWERS
AND THUNDERSTORMS. LITTLE TO NO RAINFALL IS EXPECTED IN THE
DESERTS. THE SNOW LEVEL IS AROUND 4500 FT THIS MORNING...AND IS
EXPECTED TO DROP TO AROUND 4000 FT TONIGHT. SNOWFALL TOTALS WILL
BE BETWEEN 1 TO 3 INCHES ABOVE 4500 FT...WITH ISOLATED AMOUNTS TO
UP TO 4 INCHES ON THE SOUTH SLOPES OF THE SAN BERNARDINO MTNS.
IN ADDITION TO PRECIPITATION...THIS SYSTEM WILL BRING WEST WINDS
WITH GUSTS UP TO 40 MPH IN THE MTNS AND DESERTS SUNDAY AFTERNOON
AND EVENING FOLLOWING FRONTAL PASSAGE. AS THE COLD AIR MOVES IN
FROM THE NORTHWEST...HIGH TEMPERATURES THIS WEEKEND WILL BE
ANYWHERE FROM 10 TO 20 DEGREES BELOW SEASONAL AVERAGES.
WEAK OFFSHORE FLOW WILL DEVELOP FOR MONDAY MORNING AS THE LOW
PRESSURE TROUGH MOVES EAST AND SURFACE HIGH PRESSURE MOVES INTO
THE GREAT BASIN. DESPITE THE OFFSHORE FLOW...COLD AIR MOVING IN
FROM THE NORTH WILL PREVENT MUCH WARMING FROM OCCURRING SO EXPECT
TEMPERATURES TO REMAIN BELOW SEASONAL AVERAGES. BEYOND
MONDAY...THERE IS QUITE A BIT OF UNCERTAINTY IN THE FORECAST AS
MODELS CONTINUE TO BE VERY INCONSISTENT WITH THE TRACK OF ANOTHER TROUGH
FOR TUE INTO WED. THE GFS AND EC HAVE TRENDED MUCH FURTHER WEST
WITH THIS TROUGH...BRINGING IT DOWN ALONG THE CA COAST. THIS
WOULD MEAN WEAKER UPPER SUPPORT FOR THE OFFSHORE WINDS TUESDAY AND
SLIGHTLY COOLER WEATHER. BOTH MODELS EVEN SHOW SOME RAIN OFF THE
COAST...THOUGH AT THIS TIME IT IS TOO FAR WEST TO IMPACT SOUTHERN
CA. STILL EXPECTING SOME INCREASE IN THE OFFSHORE WINDS LATE
TUESDAY INTO WED AS WINDS ALOFT TURN NORTHEAST AND SURFACE
GRADIENTS TIGHTEN. WEAK OFFSHORE WINDS AND GRADUAL WARMING WILL
CONTINUE INTO THE WEEKEND WITH TEMPS NEAR TO SLIGHTLY BELOW
NORMAL. MODELS ARE STILL HINTING AT ANOTHER LOW PRESSURE SYSTEM
FOR NEXT WEEKEND...THOUGH UNCERTAINTY IS HIGH AS THERE IS LITTLE
OR NO AGREEMENT AMONG THE MODELS AT TO WHERE THE LOW/TROUGH WILL
TRACK AND HOW STRONG IT WILL BE.
&&
.AVIATION...
291550Z...COASTAL TO MOUNTAINS AREA OF EXTREME SOUTHERN
CALIFORNIA...CLOUDS CONTINUE TO INCREASE ACROSS THE AREA AND A
FEW SHOWERS ARE BEGINNING TO SHOW UP ON RADAR AND IN OBS AT A FEW
AIRPORTS. STORM SYSTEM IS ON TRACK WITH FOCUS ON ECMWF...LOCAL
WRF AND RAP IN DECENT AGREEMENT WITH FRONTAL PASSAGE AND
SHOWERS...PER TAFS...IN THE KSNA 29/2000Z TO KSAN 30/0100Z.
CEILINGS AND WINDS NOT A MAJOR ISSUE WITH CEILINGS MAYBE TEMPO TO
015 MSL AND VSBY TO 3 MI WITH RA THE OBSCURATION. FORECAST
CONFIDENCE HIGH.
&&
.MARINE...
A HIGH SURF ADVISORY AND A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
WILL BEGIN THIS AFTERNOON AND CONTINUE SUNDAY. HAZARDOUS SEAS WILL
BE MAINLY SOUTH OF SAN CLEMENTE ISLAND. HIGHEST SURF WILL BE IN
SOUTHERN SAN DIEGO COUNTY. AN ISOLATED THUNDERSTORM IS POSSIBLE
TODAY AND EARLY SUNDAY. FORECAST CONFIDENCE MEDIUM TO HIGH...SURF
MIGHT BE MORE IMPRESSIVE THAN FORECAST IN NORTH SD AND ORANGE
COUNTIES.
ANOTHER LARGE SWELL ARRIVES NEW YEARS DAY AND CONTINUES INTO
THURSDAY. HIGH SURF ADVISORIES MAY BE NEEDED THEN.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY FROM 2 PM THIS AFTERNOON TO 2 PM PST SUNDAY
FOR THE SAN DIEGO COUNTY COASTAL AREAS.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM THIS AFTERNOON
TO 2 PM PST SUNDAY FOR THE WATERS FROM SAN MATEO POINT TO
THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN
CLEMENTE ISLAND.
&&
PUBLIC...PG
AVIATION/MARINE...PIERCEHAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE SAN DIEGO CA 900 AM PST SAT DEC 29 2012 CAZ042-043-048-050-055>058-060>062-PZZ750-775-301300- ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS- SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE- SAN DIEGO COUNTY VALLEYS-SAN BERNARDINO COUNTY MOUNTAINS- RIVERSIDE COUNTY MOUNTAINS-SANTA ANA MOUNTAINS AND FOOTHILLS- SAN DIEGO COUNTY MOUNTAINS-APPLE AND LUCERNE VALLEYS- COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS- COASTAL WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER AND OUT 30 NM- WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND- 900 AM PST SAT DEC 29 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF EXTREME SOUTHWESTERN CALIFORNIA. .DAY ONE...TODAY AND TONIGHT. A TROUGH OF LOW PRESSURE WILL BRING LIGHT TO LOCALLY MODERATE SHOWERS WITH ISOLATED THUNDERSTORMS OVER AND WEST OF THE MOUNTAINS THIS MORNING THROUGH TONIGHT. THUNDERSTORMS MAY PRODUCE SMALL HAIL...BRIEF HEAVY RAIN...AND GUSTY WINDS. SEE THE SPECIAL WEATHER STATEMENT FOR MORE DETAILS. A LONG-PERIOD WEST-NORTHWEST SWELL WILL BRING SURF UP TO 8 FEET ALONG EXPOSED WEST FACING BEACHES FROM CARDIFF SOUTHWARD THIS AFTERNOON THROUGH EARLY SUNDAY AFTERNOON. A HIGH SURF ADVISORY IS IN EFFECT FOR THAT TIME PERIOD. PLEASE SEE LAXCFWSGX FOR MORE DETAILS. THE WEST-NORTHWEST SWELL...IN ADDITION TO HIGHER WIND WAVES WITH THE INCOMING STORM SYSTEM...WILL BRING COMBINED SEAS UP TO 10 FEET THIS AFTERNOON THROUGH EARLY SUNDAY AFTERNOON FOR THE OUTER COASTAL WATERS WEST AND SOUTH OF SAN CLEMENTE ISLAND. A SMALL CRAFT ADVISORY GOES INTO EFFECT FOR THAT TIME PERIOD. PLEASE SEE LAXMWWSGX FOR MORE DETAILS. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. SHOWERS AND POSSIBLE THUNDERSTORMS WILL CONTINUE INTO SUNDAY NIGHT. THUNDERSTORMS MAY PRODUCE SMALL HAIL...BRIEF HEAVY RAIN...AND GUSTY WINDS. HIGH SURF ALONG THE SAN DIEGO COUNTY COAST AND LARGE COMBINED SEAS IN THE OUTER COASTAL WATERS WILL CONTINUE THROUGH SUNDAY AFTERNOON. WEAK TO OCCASIONALLY MODERATE OFFSHORE FLOW WILL DEVELOP FOR MONDAY MORNING THROUGH MOST OF NEXT WEEK. WINDS ARE EXPECTED TO PEAK LATE TUESDAY INTO WEDNESDAY AFTERNOON. .SPOTTER INFORMATION STATEMENT... SKYWARN WEATHER ACTIVATION IS NOT NEEDED FOR THESE AREAS...HOWEVER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS. SS/PG
The Santa Ana Mts radar (KSOX), 57 km away, was scanning. The volume nearest the first event began at 17:31 UTC.
1 waterspout. Local standard time, as filed.
A pilot reported a waterspout 19 miles WNW of Oceanside.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Eastern Pacific Coastal Waters in 2012Every state in 2012This day in weather history
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: 423436.