A line of elevated thunderstorms developed during the morning of the 20th over the ocean and along the coast ahead of an approaching upper-level low. Dynamic lift and monsoonal moisture led to further destabilization and increasing storm intensity with time.
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The episode as NWS SGX wrote it up.
A line of elevated thunderstorms developed during the morning of the 20th over the ocean and along the coast ahead of an approaching upper-level low. Dynamic lift and monsoonal moisture led to further destabilization and increasing storm intensity with time. The initial band moved inland and organized thunderstorms with prolific lightning persisted over the Inland Empire and Riverside County mountains. The coastal and valley locations of San Diego and Riverside Counties received anywhere from a few hundredths of an inch of rain to one-half of an inch, with the greatest amounts in the Inland Empire and northern San Diego County valleys. The upper low moved across San Diego and Imperial Counties on the 21st, producing intense thunderstorms over the mountains and deserts, as well as a significant dust storm that moved up the Coachella Valley. The mountain locations of San Diego and Riverside Counties received up to one-half of an inch of rain, while the San Diego County deserts received up to 1.30 inches. One-inch hail was reported with thunderstorms in Nuevo and Mount Laguna/Pine Valley.
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 20, 2:34 AM PST, 1 hour 26 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 334 AM PDT WED AUG 20 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL MOVE THROUGH SOUTHERN CALIFORNIA THROUGH THURSDAY AND BRING CHANCES FOR SHOWERS AND THUNDERSTORMS TO MUCH OF THE REGION. TEMPERATURES WILL BE BELOW NORMAL WITH NIGHT AND MORNING LOW CLOUDS IN COASTAL AND VALLEY AREAS. FAIR AND WARMER WEATHER WILL RETURN FRIDAY AS THE LOW PRESSURE EXITS TO THE EAST...WITH FEWER LOW CLOUDS AND ONLY MINOR DAY TO DAY FLUCTUATIONS IN TEMPERATURES OVER THE WEEKEND. FURTHER WARMING IS POSSIBLE EARLY NEXT WEEK TO NEAR NORMAL LEVELS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... THE UPPER LOW PRESSURE IS CENTERED NEAR THE CHANNEL ISLANDS EARLY THIS MORNING. THIS FEATURE WILL BRIEFLY CUTOFF THROUGH THURSDAY EVENING BEFORE BEING EJECTED EAST TOWARDS THE 4 CORNERS FRIDAY AND OPENING UP. HI-RES MODELS IN GOOD AGREEMENT WITH THE UPPER LOW FEATURE WITH A NARROW TAP OF SUBTROPICAL MOISTURE CONTINUING THROUGH THURSDAY MORNING AND GENERATING SCATTERED CONVECTION AT TIMES. THE THREAT OF CONVECTION WILL CONTINUE THIS MORNING ACROSS THE COASTAL SECTOR AND THROUGH THE INLAND EMPIRE. WE EXPECT THE AREA OF CONVECTION FOCUS TO TRANSITION TO THE INLAND MOUNTAINS AND DESERTS LATER THIS AFTERNOON AND EVENING WITH DIURNAL HEATING ALTHOUGH AN ISOLATED THUNDERSTORM CANNOT BE RULED OUT THROUGH THURSDAY MORNING ACROSS THE COASTAL REGION TOO. THE CONVECTION THIS MORNING HAS BEEN PERSISTENT SINCE ABOUT MIDNIGHT AND ALONG A TRAINING BAND FROM THE NEARSHORE WATERS NEAR SAN CLEMENTE ISLAND TO NEAR OCEANSIDE HARBOR...AND INLAND TO NEAR ONYX PEAK. HI-RES CONVECTIVE PARAMETERS INDICATE SURFACE BASED INSTABILITY WILL BE FAIRLY IMPRESSIVE ACROSS THE INLAND MOUNTAINS THIS AFTERNOON WITH CAPE VALUES REACHING 1000+ J/KG. RESIDUAL MOISTURE PRIMARILY FOR INLAND AREAS WILL CONTINUE THE THREAT OF CONVECTION THROUGH THURSDAY MORNING BEFORE OUR REGION IS PLACED ON THE BACKSIDE OF THE UPPER LOW. ONSHORE FLOW...ALBEIT NOT AS STRONG...WILL CONTINUE THROUGH THE WEEKEND. THIS WILL CONTINUE TO BRING SLIGHTLY BELOW NORMAL TEMPERATURES ALONG THE COAST AND ACROSS THE COASTAL VALLEYS TOO. THE HIGH PRESSURE ZONE WILL BUILD WEST FROM THE DESERT SOUTHWEST AND BRING A MINOR WARMUP EARLY NEXT WEEK. TEMPERATURES WILL WARM UP BUT ARE NOT EXPECTED TO EXCEED LATE AUGUST NORMALS THROUGH EARLY NEXT WEEK. && .AVIATION... 201000Z...PATCHY STRATUS...WITH BASES FROM 2100-2500 FT MSL AND TOPS TO 3100 FT MSL...WILL CONTINUE ALONG PORTIONS OF THE COAST AND COASTAL VALLEYS THIS MORNING. SCATTERED THUNDERSTORMS MOVING NORTHEAST...STRETCHING FROM THE COASTAL WATERS NEAR KCRQ INLAND TO THE MOUNTAINS NEAR KRIV...WILL CONTINUE SLOWLY SOUTHWARD THIS MORNING. LIGHTNING...SMALL HAIL AND GUSTY WINDS WILL BE POSSIBLE NEAR STORMS. THUNDERSTORMS CHANCES WILL CONTINUE THROUGH THURSDAY MORNING ACROSS THE REGION. PATCHY STRATUS WILL CLEAR TOWARDS THE COAST LATE THIS MORNING...THEN REDEVELOP ALONG THE COAST TONIGHT WITH SLIGHTLY LOWER TOPS AND BASES. && .MARINE... 300 AM...SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTHEAST ACROSS THE COASTAL WATERS THROUGH LATE THIS MORNING. CLOUD-TO-WATER LIGHTNING...GUSTY WINDS...SMALL HAIL...ROUGH SEAS AND ISOLATED WATERSPOUTS MAY ACCOMPANY STORMS. THE POSSIBILITY OF SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THURSDAY MORNING. A MARINE WEATHER STATEMENT REMAINS IN EFFECT FOR THUNDERSTORMS OVER THE COASTAL WATERS THROUGH THURSDAY MORNING. && .SKYWARN... SKYWARN ACTIVATION MAY BE REQUESTED LATER TODAY DUE TO THUNDERSTORMS. WEATHER SPOTTERS ARE ENCOURAGED TO REPORT ANY OBSERVED SIGNIFICANT WEATHER CONDITIONS. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && PUBLIC...BROTHERTON AVIATION/MARINE...JJT
The Santa Ana Mts radar (KSOX), 46 km away, was scanning. The volume nearest the first event began at 12:01 UTC.
3 hail, 1 lightning, 1 flash flood, 1 dust storm, 1 flood. Local standard time, as filed.
The public reported 1-inch hail in Menifee from an early morning thunderstorm. Local news media reported large hail cracked a vehicle windshield in Menifee from the same storm.
A spotter reported hail up to one inch in Nuevo from a thunderstorm.
A spotter reported lightning struck and ignited fires in two palm trees near the community college. The fires were put out. Lightning also struck the technology building on campus, knocking out power.
One inch plus hail reported by the observers at the Mt. Laguna Observatory.
A spotter in Campo reported flash flooding and pea size hail at CA Highway 94 and Shookey road.
A spotter reports a dust storm producing quarter mile visibility in Cathedral City, with winds estimated at 15-20 mph. A haboob in Palm Springs felled a tree onto a pickup truck containing a man who was injured and taken to the hospital. Peak wind speeds at the nearby Palm Springs ASOS were 40 mph at that time. The dust storm then proceeded down the Coachella Valley, reaching the Thermal Airport, whose ASOS reported one-quarter mile visibility in dust and 40 knot wind gusts.
A ham radio spotter is reporting up to 6 inches of water on the road in the 35000 block of Highway 79 near Warner Springs.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2014Every state in 2014This day in weather historyWarnings in California, August 2014
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: 539664, 539667, 539670, 539671, 539672, 539674, 539673.