Mean layer troughing positioned over SE Georgia as upper level divergence increased within the right rear quadrant of the upper level jet stream. Lingering outflow boundaries and active sea breezes in concert with a very moist and unstable airmass combined with the dynamical convective triggers to support widespread flooding and isolated severe storms during the afternoon and evening.
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 JAX wrote it up.
Mean layer troughing positioned over SE Georgia as upper level divergence increased within the right rear quadrant of the upper level jet stream. Lingering outflow boundaries and active sea breezes in concert with a very moist and unstable airmass combined with the dynamical convective triggers to support widespread flooding and isolated severe storms during the afternoon and evening.
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 Jacksonville, FL wrote its last area forecast discussion before the first event at Aug 20, 8:20 AM EST, 3 hours 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 920 AM EDT MON AUG 20 2012 .UPDATE... LARGE UPPER LEVEL TROUGH CONTINUES FROM THE GREAT LAKES TO THE GULF OF MEXICO. A FRONTAL BOUNDARY MEANDERS FROM SRN MISSISSIPPI ACROSS GA TO NC COAST. MORNING SOUNDINGS FROM NEARBY LOCATIONS SHOW DEEP SOUTHWESTERLY FLOW OVER THE REGION AND SATELLITE SHOWS A CONVEYOR BELT OF MOISTURE ON THE ERN EDGE OF THE TROUGH STREAMING ACROSS THE GULF OVER THE FORECAST AREA TO THE MID ATLANTIC REGION. A SERIES OF SHORTWAVES WILL RIDE THROUGH THIS MOISTURE BAND OVER THE NEXT COUPLE DAYS. TEMPERATURES AT 500 MB ARE AROUND -7C AND PWATS ARE NEAR OR ABOVE 2 INCHES. PERIODS OF HEAVY RAIN ARE EXPECTED WITH NUMEROUS TO WIDESPREAD SHOWERS/STORMS. CLOUDS AND RAIN WILL LIMIT MAX TEMPS AND EXPECT MID 80S AT BEST FOR MUCH OF THE AREA WITH UPPER 80S OVER THE SOUTH PORTION. STRONGER STORMS ARE MORE LIKELY OVER NE FL WHERE SUFFICIENT HEATING WILL DESTABILIZE THE ATMOSPHERE AND OUTFLOWS AND SEA BREEZES WILL CONTRIBUTE TO UPLIFT. OTHER THAN HEAVY RAINFALL...MAIN CONCERN WILL BE STRONG GUSTY WINDS AND ISOLATED SEVERE ARE POSSIBLE ESPECIALLY NE FL...BUT SPC HAS 5% CHANCE FOR THE ENTIRE FORECAST AREA. && .AVIATION... HAVE AMENDED TAFS TO KEEP LIFR CIGS UNTIL 15Z AND THEN MVFR AS SHOWERS/STORMS MOVE INTO THE REGION. && .MARINE... SOUTHWEST WINDS PEAKED DURING THE PRE-DAWN HOURS...THEN BEGAN DECREASING AT 12Z. SINCE THE NOCTURNAL SURGE IS PAST...WILL DROP THE SCEC HEADLINE FOR OFFSHORE LEGS AND GO WITH 15 KT FOR REMAINDER OF THE DAY. SEAS ARE RUNNING 1 TO 3 FT. RIP CURRENTS: LOW RISK EARLY IN THE WEEK. && .PRELIMINARY POINT TEMPS/POPS... AMG 85 72 84 72 / 60 60 60 50 SSI 85 75 84 74 / 60 60 60 50 JAX 87 74 86 72 / 70 70 70 50 SGJ 88 74 86 73 / 70 60 60 40 GNV 86 72 84 72 / 80 70 70 50 OCF 87 73 86 73 / 70 60 60 50 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && MKT/AW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE JACKSONVILLE FL 334 AM EDT MON AUG 20 2012 AMZ450-452-454-470-472-474-FLZ020>025-030>033-035>038-040- GAZ132>136-149>154-162>166-210833- ALTAMAHA SOUND GA TO FERNANDINA BEACH FL OUT 20 NM- FERNANDINA BEACH TO ST AUGUSTINE FL OUT 20 NM- ST AUGUSTINE TO FLAGLER BEACH FL OUT 20 NM- ALTAMAHA SOUND GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE- FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE- ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE-HAMILTON- SUWANNEE-COLUMBIA-BAKER-NASSAU-DUVAL-UNION-BRADFORD-CLAY-ST JOHNS- GILCHRIST-ALACHUA-PUTNAM-FLAGLER-MARION-COFFEE-JEFF DAVIS-BACON- APPLING-WAYNE-ATKINSON-WARE-PIERCE-BRANTLEY-INLAND GLYNN- COASTAL GLYNN-ECHOLS-CLINCH-CHARLTON-INLAND CAMDEN-COASTAL CAMDEN- 334 AM EDT MON AUG 20 2012 ...LOCALLY HEAVY RAINFALL POSSIBLE THROUGH MUCH OF THE WEEK... ...ISOLATED STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON... THIS OUTLOOK IS FOR NORTHEAST FLORIDA...SOUTHEAST GEORGIA AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT... ISOLATED THUNDERSTORMS MAY DEVELOP NEAR THE I-75 CORRIDOR OF INLAND NORTHEAST FLORIDA BEFORE DAWN THIS MORNING. AFTER SUNRISE...SHOWER AND THUNDERSTORM ACTIVITY WILL BECOME MORE NUMEROUS. ACTIVITY WILL TRACK TO THE EAST NORTHEAST AROUND 15 TO 20 MPH. PERIODS OF HEAVY RAINFALL ARE LIKELY TODAY WITH LOCAL AMOUNTS OF 2 TO 3 INCHES POSSIBLE. DURING THE AFTERNOON AND EVENING A FEW ISOLATED STRONG TO SEVERE STORMS MAY DEVELOP. WIND GUSTS OF 40 TO 60 MPH AND HAIL WILL BE THE MAIN CONCERNS IN STRONGER STORMS AS WELL AS FREQUENT LIGHTNING. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY... A FRONTAL BOUNDARY WILL STALL OVER THE REGION TUESDAY THROUGH MIDWEEK WHICH WILL TRIGGER NUMEROUS TO SCATTERED SHOWERS AND THUNDERSTORMS EACH AFTERNOON AND EVENING. SCATTERED STRONG STORMS ARE EXPECTED... WITH GUSTY WINDS...FREQUENT LIGHTNING STRIKES...AND WIDESPREAD HEAVY DOWNPOURS. WIDESPREAD RAINFALL TOTALS OF 2 TO 5 INCHES ARE EXPECTED ACROSS SOUTHEAST GEORGIA AND NORTHEAST FLORIDA...AND LOCALIZED FLOODING IS POSSIBLE DURING HEAVIER DOWNPOURS. DRIER AIR WILL FILTER OVER SOUTHEAST GEORGIA ON THURSDAY...THEN OVER NORTHEAST FLORIDA ON FRIDAY...WHICH WILL BRING LOWER RAIN CHANCES INTO NEXT WEEKEND. EASTERLY FLOW IS EXPECTED EARLY NEXT WEEK...AND AN INCREASE IN RIP CURRENT RISK IS ANTICIPATED. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS REQUESTED TODAY IF FLOODING IS OBSERVED...OR IS WARNINGS ARE ISSUED LATER TODAY. FOR ADDITIONAL INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN JACKSONVILLE WEBSITE ON THE INTERNET AT WEATHER.GOV/JAX. ABE
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JACKSONVILLE FL
1127 AM EDT MON AUG 20 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0302 PM LIGHTNING BUNNELL 29.47N 81.26W
08/19/2012 FLAGLER FL EMERGENCY MNGR
LIGHTNING STRUCK AN ANTENNA ON THE FLAGLER COUNTY
EMERGENCY OPERATIONS CENTER. THE ANTENNA WAS BLOWN TO
PIECES. THE LIGHTNING PROTECTION SYSTEM WORKED. NO OTHER
DAMAGE WAS REPORTED TO THE BUILDING.
&&
MTRABERTSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSONVILLE FL
1211 PM EDT MON AUG 20 2012
FLZ021-201645-
SUWANNEE-
1211 PM EDT MON AUG 20 2012
...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED FOR SOUTHEASTERN
SUWANNEE COUNTY FOR STRONG WINDS AND FUNNEL CLOUDS VALID UNTIL 1245
PM EDT...
AT 1212 PM EDT NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CENTERED 8 MILES WEST OF BRANFORD...OR 9 MILES
SOUTHEAST OF MAYO...MOVING NORTHEAST AT 20 MPH. THIS STRONG
THUNDERSTORM WILL ALSO AFFECT AREAS AROUND BRANFORD...OBRIEN...
MCALPIN...ICHETUCKNEE SPRINGS STATE PARK AND HILDRETH THROUGH 1245 PM
EDT. GUSTY WINDS OF 45 TO 55 MPH CAN BE EXPECTED ALONG WITH POSSIBLE
MINOR DAMAGE. DOPPLER RADAR HAS INDICATED WEAK ROTATION WITHIN THIS
STORM. TORNADOES MAY DEVELOP WITH LITTLE OR NO ADVANCE WARNING. HEAVY
RAINFALL WILL PRODUCE PONDING OF WATER ON ROADWAYS AND MINOR FLOODING
OF LOW-LYING AREAS. IF FURTHER INTENSIFICATION OCCURS A WARNING MAY
BE REQUIRED.
REPORT DAMAGE TO THE NEAREST LAW ENFORCEMENT AGENCY OR YOUR COUNTY
EMERGENCY MANAGEMENT.
LAT...LON 3026 8287 3012 8279 2999 8279 2999 8276
2997 8276 2993 8280 2989 8289 2989 8292
2995 8293 2995 8295 2999 8297 3007 8307
3009 8308
TIME...MOT...LOC 1612Z 238DEG 16KT 2999 8303
HESSThe national radar mosaic for the moment the first event began.
5 heavy rain, 3 thunderstorm wind, 2 lightning, 1 hail, 1 flood. Local standard time, as filed.
Trees were blown down in Fort White. One damaged a home. The time of the event was based on radar.
A lightning strike hit a home on Tortuga Bay Drive which caused a structure fire. The time of the incident was based on lightning data. The cost of damage was estimated.
The Green Cove Springs Post Office observed nickel size hail near State Road 16 and County Road 218.
Trees were blown down along Sherwood Avenue.
Widespread areal flooding occurred across downtown Jacksonville from the Westside of town to Mandarin, and northward to Arlington and the Northside. At 3:45 pm, Duval County Emergency Management reported cars were stranded due to flooded roads throughout the San Marco area. At 3:55 pm, law enforcement reported the Powers Road from Toledo Road to University Blvd was closed due to flooding. At 4 pm, emergency management reported flooding along Blanding Blvd near Interstate 295 in Argyle. At 4 pm, emergency management also stated a roof collapsed at an apartment complex along San Jose Blvd due to heavy rainfall. At 4:06 pm, the media reported a car was trapped by flood waters in Argyle. At 4:18 pm, the media reported a home was flooded in Ortega with water rescues by fire officials. At 4:18 pm, emergency management reported water was entering a home in Englewood. The car of the homeowner was flooded and there was widespread street flooding in the area. At 4:26 pm, a spotter reported a drainage ditch overflowed and caused flooding on Harlow Blvd. The spotter also measured 3.2 inches of storm total rainfall. At 4:53 pm, emergency management reported a vehicle stuck in flood waters in San Marco. At 5:01 pm, emergency management reported a sinkhole behind an apartment complex near Naval Air Station Jacksonville. At 5:11 pm, emergency management reported water entered a home near Bowden Road close to University Blvd. At 5:12 pm, emergency management reported water entered a home in San Marco. AT 5:12 pm, emergency management reported street flooding over Sabena Road near University Blvd. At 5:15 pm, the media reported significant inundation due to flooding at the intersection of McCoys Creek Blvd and Stockton Street in downtown Jacksonville. At 5:15 pm, the media reported inundation due to flood waters near the intersection of Roosevelt Blvd and South Edgewood Ave in the Avondale area of downtown Jacksonville. At 5:16 pm, emergency management reported flooded streets in southside Jacksonville between Atlantic Blvd and Beach Blvd near University Blvd South. At 5:18 pm, emergency management reported a vehicle stuck in flood waters in the southbound lane of the approach to the Buckman Bridge. At 5:25 pm, emergency management reported that north Main Street and Zoo Parkway were closed due to flooding and the concrete cracking underneath an overpass and shifting. At 5:27 pm, emergency management reported a sinkhole on University Blvd North and Arlington Road. At 5:30 pm, emergency management reported a vehicle stuck in flood waters in the San Jose area of Jacksonville. The cost of damage was estimated, and it is likely grossly underestimated.
Power lines were down across A1A due to a lightning strike. The cost of repair was estimated.
A tree was blown down over the road in Cedar Point. The cost of debris removal was estimated.
Naval Air Station Jacksonville measured a 12 hour rainfall of 3.84 inches. The one hour total of 3.45 inches occurred between 3 and 4 pm.
A storm total amount of 3.17 inches was measured.
The public measured 2.93 inches of storm total rainfall.
The public measured 4.86 inches of rainfall.
Craig Airport measured a 12 hour rainfall of 2.68 inches. One hour rainfall accumulation was 2.43 inches between 3 pm and 4 pm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2012Every state in 2012This day in weather historyWarnings in Florida, August 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: 399453, 399440, 399448, 399454, 399416, 399421, 399450, 399441, 399443, 399444, 399445, 399446.