A surge of monsoonal moisture brought three days of significant thunderstorms from the 26th to the 28th. These storms brought more CG lightning, strong wind gusts in the low 50s mph, 1/2 -3/4 hail and brief heavy downpours.
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.
A surge of monsoonal moisture brought three days of significant thunderstorms from the 26th to the 28th. These storms brought more CG lightning, strong wind gusts in the low 50s mph, 1/2 -3/4 hail and brief heavy downpours. Minor accumulation from small hail occurred with some of these storms. The rain produced some flash flooding at low water crossings in Chihuahua Valley. Street flooding and 1/2 hail was also reported near Big Bear in the San Bernardino Mountains. Lightning sparked several small fires in the Riverside and San Bernardino County mountains, including one that became the Oasis Fire.
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 Aug 26, 8:00 AM PST, 4 hours 45 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 900 AM PDT FRI AUG 26 2011 .SYNOPSIS... STRONG HIGH PRESSURE WILL BRING HOT WEATHER TO INLAND AREAS THROUGH THE WEEKEND. MONSOONAL MOISTURE IS EXPECTED TO BRING SCATTERED THUNDERSTORMS THIS AFTERNOON AND EARLY EVENING TO THE MOUNTAINS...DESERTS...AND INLAND VALLEYS. MOISTURE WILL BEGIN TO DECREASE ON SATURDAY WITH A SLIGHT CHANCE OF AFTERNOON AND EARLY EVENING THUNDERSTORMS IN THE MOUNTAINS AND DESERTS. A TROUGH OF LOW PRESSURE NEAR THE WEST COAST WILL BRING A COOLING AND DRYING TREND NEXT WEEK WITH A RETURN OF THE MARINE LAYER WITH NIGHT AND MORNING LOW CLOUDS AND FOG FOR COASTAL AREAS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A WAVE OF MID LEVEL CLOUDS WITH VERY ISOLATED SHOWERS PUSHED THROUGH THE REGION EARLY THIS MORNING. EVEN A COUPLE THUNDERSTORMS DEVELOPED OFFSHORE JUST WEST OF SAN CLEMENTE ISLAND. MOISTURE HAS INCREASED AND WITH MOSTLY CLEAR SKIES TO ENHANCE SURFACE HEATING...THE PUMP IS PRIMED FOR SOME THUNDERSTORMS TODAY. THE STEERING FLOW AT AROUND 10-15 THOUSAND FEET WILL TURN EAST AND THAT WILL HELP DRIFT A FEW OF THOSE TSTORMS INTO THE VALLEYS THIS AFTERNOON. THE MOISTURE IS NOT SUPER IMPRESSIVE BUT THE TSTORMS WILL MOVE SLOWLY...SO THE FLASH FLOOD POTENTIAL IS MODERATE TODAY IN THE MOUNTAINS. MEANWHILE BACK AT THE COAST THERE WAS ONLY ONE LITTLE HUNK OF FOG AROUND LA JOLLA THAT WE COULD FIND. I GUESS THEY DIDN'T GET THE MEMO. IN GENERAL THE MARINE LAYER AND ITS COASTAL CLOUDS WILL BE VERY DIMINISHED AND ALMOST NON-EXISTENT THROUGH THE WEEKEND. THE HOT WEATHER WILL PEAK TODAY AND SATURDAY. INLAND TEMPS WILL BE ABOUT 6 TO 12 DEGREES HIGHER THAN AVERAGE AND THAT WILL PUT A LOT OF INLAND CITIES AND THE HIGH DESERT WELL INTO THE 100S AND THE LOWER DESERT ABOVE 110. AT THIS TIME HEAT INDEX VALUES ARE EXPECTED TO STAY JUST BELOW HEAT WARNING CRITERIA. MOISTURE GRADUALLY DECREASES SATURDAY AND SUNDAY AND SO DO THE CHANCES OF THUNDERSTORMS EACH AFTERNOON. ON MONDAY THE STRONG HIGH PRESSURE RIDGE OVER THE SOUTHWEST WILL BEGIN TO WEAKEN AS A WEAK TROUGH OF LOW PRESSURE DEVELOPS ALONG THE WEST COAST. THIS WILL BRING A COOLING TREND AND A MORE APPARENT MARINE LAYER WILL RETURN MONDAY THROUGH AT LEAST NEXT THURSDAY. && .AVIATION... 261555Z...STRATUS IS JUST ABOUT DISSIPATED AND AIR MASS IS PRIMED AND READY FOR THUNDERSTROM DEVELOPMENT ACROSS SOUTHERN CALIFORNIA TODAY. TRIGGER TEMPS SHOULD BE REACHED BY 1800 UTC. BETWEEN 1800-27/0300 UTC SCT-BKN CUMULONIMBUS OVER MOUNTAINS WITH BASES FL090-120 AND TOPS TO FL450...MOVING TOWARDS THE NORTHWEST. BETWEEN 27/0300-27/1600 UTC...BROKEN CONVECTIVE DEBRIS CLOUDS BETWEEN FL150-FL250. THESE SHOULD LIMIT DEVELOPMENT OF LOW STRATUS OVER WATER/IMMEDIATE COAST TO FEW-SCT AOB FL007. AFTER 27/1800 UTC EXPECT SIMILAR THUNDERSTORM DEVELOPMENT BUT DIRECTION OF CELL MOVEMENT TO THE NORTH IN THE MORNING HOURS AND TOWARDS THE NORTHEAST DURING THE AFTERNOON HOURS AS WINDS VEER FROM SOUTH TO SOUTHWEST. && .MARINE... SINCE 0620 PDT...INFREQUENT CLOUD TO WATER LIGHTNING STRIKES HAVE BEEN OBSERVED OVER THE OFFSHORE WATERS...ABOUT 15-20 NM W OF SAN CLEMENTE ISLAND...FROM ELEVATED CONVECTION. CLOUD BASES ARE ABOVE 10000 FT MSL. DUE TO THE STABLE BOUNDARY LAYER...BETWEEN THE SEA SURFACE AND 2500 FEET MSL...DOWNDRAFTS AND RAIN ARE NOT LIKELY TO REACH THE SEA SURFACE...AND SINCE THE THUNDERSTORM CELLS ARE LIKELY TO CONTINUE TRACKING TOWARDS THE NORTH AND THE SUPPORT FOR ELEVATED CONVECTION SHOULD TEMPORARILY END AFTER 1000 PDT...LIGHTNING STRIKES OVER THE OUTER COASTAL WATERS...IN MARINE ZONE PZZ775...ARE NOT EXPECTED TODAY. THERE IS A POSSIBILTY OF NOCTURNAL ELEVATED THUNDERSTORMS AGAIN TONIGHT/SATURDAY MORNING. AFTER SATURDAY MORNING THE AIR MASS SHOULD BECOME DRY AND STABLE OVER THE COASTAL WATERS AS THE FLOW ALOFT BECOMES SOUTHWEST. LOOKING FURTHER AHEAD...A SIGNIFICANT SOUTHERN HEMISPHERE SWELL IS STILL FORECAST TO ARRIVE LATE NEXT WEEK. THE WAM III MODEL IS BACKING OFF ON THE ARRIVAL TIME AND INCREASING THE PEAK...WHICH IS CONSISTENT WITH PREVIOUS PERFORMANCE OF THE MODEL...BEING TOO FAST AND TOO LOW OF SOUTHERN HEMISPHERE SWELLS. EITHER WAY AT LEAST 4-5 FOOT 20 SECOND SWELL FROM 200 DEGREES IS LIKELY THURSDAY SEPTEMBER 1 WITH SURF HEIGHTS 10 FEET FOR SOUTH FACING BEACHES. && .SGX WATCHES/WARNINGS/ADVISORIES... SPECIAL WEATHER STATEMENT FOR THE HEAT...SEE LAXSPSSGX. && PUBLIC...MM AVIATION...BALFOUR
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN DIEGO CA 355 AM PDT FRI AUG 26 2011 CAZ042-043-048-050-055>058-060>062-270100- 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- 355 AM PDT FRI AUG 26 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF EXTREME SOUTHWESTERN CALIFORNIA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON THROUGH EARLY EVENING FOR THE MOUNTAINS...DESERTS...AND INLAND VALLEYS. THE FLASH FLOOD POTENTIAL INDEX IS MODERATE...THUNDERSTORMS ARE EXPECTED TO DEVELOP AND ISOLATED FLASH FLOODING IS POSSIBLE. FOR INLAND AREAS...IT WILL BE HOT AND HUMID THIS AFTERNOON. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY FOR SATURDAY AFTERNOON AND EARLY EVENING...THERE IS A SLIGHT CHANCE OF THUNDERSTORMS FOR THE MOUNTAINS...DESERTS...AND INLAND VALLEYS. THE FLASH FLOOD POTENTIAL INDEX IS LOW...THE RISK OF FLASH FLOODING IS MINIMAL. FOR SATURDAY AND SUNDAY...CONTINUED HOT AND HUMID FOR INLAND AREAS. .SPOTTER INFORMATION STATEMENT... SKYWARN WEATHER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EARLY EVENING. MARTIN
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SAN DIEGO CA
1257 PM PDT FRI AUG 26 2011
CAZ058-062-262100-
SAN DIEGO COUNTY DESERTS-
SAN DIEGO COUNTY MOUNTAINS-
1257 PM PDT FRI AUG 26 2011
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SAN DIEGO COUNTY
UNTIL 200 PM PDT...
AT 1254 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
TWO STRONG THUNDERSTORMS 20 MILES SOUTHWEST OF OCOTILLO...MOVING
SLOWLY NORTHEAST AT 5 MPH. THESE STORMS ARE LOCATED JUST ACROSS THE
MEXICO BORDER BUT WILL SEND STRONG WINDS INTO SOUTHEAST SAN DIEGO
COUNTY AND AFFECT PARTS OF INTERSTATE 8.
HAIL IS PROJECTED TO BE LESS THAN THREE-QUARTERS OF AN INCH IN
DIAMETER...AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM.
AREAS AFFECTED BY THIS STORM INCLUDE...TIERRA DEL SOL...JACUMBA...
BOULEVARD AND LIVE OAK SPRINGS.
LAT...LON 3278 11640 3273 11610 3262 11610 3261 11611
3260 11620 3261 11623 3260 11626 3259 11640
TIME...MOT...LOC 1954Z 208DEG 4KT 3256 11625
TARDYThe San Diego radar (KNKX), 62 km away, was scanning. The volume nearest the first event began at 20:45 UTC.
2 flash flood, 1 hail, 1 thunderstorm wind. Local standard time, as filed.
Nickel sized hail was reported by a spotter, along with an estimated wind gust of 45 to 55 mph.
Spotter reported street flooding on Big Bear Boulevard from the Stanfield cutoff to Pine Knot Avenue, as well as Rathbun Creek at Catalina Road. Water 6-12 inches deep covered the roadway.
Chihuahua Valley Road was impassable due to fast-moving water over the roadway, up to 2 feet deep in places. Other roads were washed out nearby. Hail up to penny-sized (3/4) was also observed along Chihuahua Valley Road, with minor accumulation of the hail.
The SDGE Mesonet, CMCSD recorded a wind gust of 65 mph during a downburst from a thunderstorm at 1400 PST on the 28th. The Campo ASOS also recorded a gust of 61 mph at 1352 PST nearby. During the time of these gusts, 5 power poles were snapped on Buckman Springs Road near Highway 94 and several large tree branches fell onto the Campo COOP observer's property. Power was lost soon after these poles and branches came down. Lightning sparked several small fires on the observer's property, but all were contained quickly. The Campo ASOS also recorded 1.02 inches of rain in 30 minutes during this storm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2011Every state in 2011This day in weather historyWarnings in California, August 2011
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: 340271, 340272, 340274, 340275.