A tropical airmass and a weak disturbance combined to produce heavy rainfall across portions of northwest Florida.
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The episode as NWS TAE wrote it up.
A tropical airmass and a weak disturbance combined to produce heavy rainfall across portions of northwest Florida.
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 Tallahassee, FL wrote its last area forecast discussion before the first event at Aug 18, 11:43 PM CST, 17 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 143 AM EDT Sun Aug 19 2012 .NEAR TERM [through Tonight]... The PoP forecast is tricky tonight as most of the guidance does not appear to have a very good handle on the large mass of rain with embedded thunderstorms approaching from the west. The 18z NAM does not know that this rain exists, and most of the hi-res guidance is struggling as well. The HRRR seems to have a fair handle on the current rain area though and moves it eastward overnight while gradually weakening. Although gradual weakening is expected, it will likely move into at least the western part of the forecast area overnight, so PoPs were raised into the likely range (60-70 percent) roughly from the Apalachicola river westward, with 30-50 percent PoPs east of there. This is only round 1 of what may be several rounds of showers with embedded thunderstorms over the next few days with a tropical airmass in place and the base of a broad upper level trough affecting the area. .SHORT TERM [Sunday through Monday Night]... Looks like a very unsettled period with the broad trough over the eastern CONUS deepening as several impulses drop southeastward from the plains into the base of the trough. The axis of the trough will remain west of the local region which will tap into the tropical moisture associated with Helene or its remnants in the deep layer southwest flow. The GFS continues to show the upper jet dipping well into the southeastern states Sunday into Monday placing the Tri-State area within the right entrance region. SPC's day 2 discussion currently mentions this put no highlighted area for a severe risk at this time. This will need to be monitored closely. At the surface, a cold front will approach from the northwest pushing into our western zones Monday possibly becoming quasi-stationary late Monday or Tuesday. As mentioned in an earlier discussion, this could set the stage for a heavy rain event with localized flooding. Understandably PoPs will be rather high during this period and will generally go above numerical guidance. Max temps will be held down a few degrees with the extensive cloud cover and convective activity. && .LONG TERM [Tuesday through Saturday]... With the mean upper level trough expected to remain quite persistent across the eastern half of the U.S. through much (if not all) of the upcoming week, impulses of energy rounding the base of the trough over the Southeast will combine with plenty of deep layer moisture to keep above normal PoPs in the fcst throughout much of the extended period. Additionally, the likely remnants of Tropical Storm Helene (which is still progged to move into southern Mexico, well away from our region), may still play an important role in our fcst before the week is over. While there are still plenty of discrepancies between the global models (and run to run differences within each model) over timing and potential moisture influx, the simple presence of the steep upper level trough, will likely pull in some deep layer tropical moisture into our region from the SW by mid to late next week. Now, the latest runs of the GFS (00 UTC) and ECMWF (12 UTC Thu), are back to showing some potential for a "break" in the organized convection later on Tue. and possibly lasting into Thu., but am not ready to buy into this solution just yet, given the numerous changes and uncertainty surrounding Helene. Should this become a trend that all of the global models begin embracing, then PoPs can be adjusted downward at a later time. Also, with the increased cloud cover which is still expected during the day, the effects of the more typical afternoon sea breeze will be somewhat limited (except for possibly Tue aftn thru Thu.), so high temps should average a bit below climo values through much of the period. While this does NOT appear to be the best stretch of "beach weather" by any means, the potential of a good stretch of widespread rainfall will certainly help many areas to continue to chip away at our long term ongoing drought. Please stay tuned to the latest fcsts from the National Weather Service, as this pattern may need some fine tuning once the global models come into better agreement with each other, and maintain more run to run consistency. && .AVIATION [through 06z Monday]... Updated at: 140am Confidence is low for this set of TAFs as there is a fair amount of disagreement amongst the models as to how SHRA and TS will evolve today. For now, we went with the idea of MVFR CIGS developing late tonight and lingering into the morning hours, with VFR thereafter. As far as timing of SHRA and TS, we went with the general idea of rapid development in the 09-12z timeframe - beginning at the Gulf coast and then spreading inland. Although there is disagreement on location and timing of convection for much of the day, models do seem to agree on an early start to things. Some MVFR/IFR is likely to exist in and near SHRA and TS for the bulk of the day. However, confidence in continued activity beyond about 18z is low, so that time frame was kept VFR across the board for now at terminals. && .MARINE... Winds will be from the southwest at least through mid-week with winds and seas gradually increasing to cautionary levels by Tuesday as the pressure gradient tightens ahead of a cold front. This front will also bring numerous showers and thunderstorms to the coastal waters. Winds and seas may subside below headline criteria on Wednesday. && .FIRE WEATHER... Typical of this wet summer pattern, afternoon relative humidities will remain well above critical levels over the next several days and, and therefore, conditions will continue to remain safely above red flag levels. && .TAE WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AL...None. GM...None. && NEAR TERM...DVD SHORT TERM...Barry LONG TERM...Gould AVIATION...Lamers MARINE...Barry FIRE WX...Block
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TALLAHASSEE FL 813 PM EDT SAT AUG 18 2012 ALZ065>069-FLZ007>019-026>029-034-108-112-114-115-118-127-128-134- GAZ120>131-142>148-155>161-GMZ730-750-755-765-770-775-191100- COFFEE-DALE-HENRY-GENEVA-HOUSTON-INLAND WALTON-CENTRAL WALTON- HOLMES-WASHINGTON-JACKSON-INLAND BAY-CALHOUN-INLAND GULF- INLAND FRANKLIN-GADSDEN-LEON-INLAND JEFFERSON-MADISON-LIBERTY- INLAND WAKULLA-INLAND TAYLOR-LAFAYETTE-INLAND DIXIE-SOUTH WALTON- COASTAL BAY-COASTAL GULF-COASTAL FRANKLIN-COASTAL JEFFERSON- COASTAL WAKULLA-COASTAL TAYLOR-COASTAL DIXIE-QUITMAN-CLAY- RANDOLPH-TERRELL-DOUGHERTY-LEE-WORTH-TURNER-TIFT-BEN HILL-IRWIN- EARLY-MILLER-BAKER-MITCHELL-COLQUITT-COOK-BERRIEN-SEMINOLE- DECATUR-GRADY-THOMAS-BROOKS-LOWNDES-LANIER- APALACHEE BAY OR COASTAL WATERS FROM KEATON BEACH TO OCHLOCKONEE RIVER FL OUT TO 20 NM- COASTAL WATERS FROM APALACHICOLA TO DESTIN FL OUT 20 NM- COASTAL WATERS FROM OCHLOCKONEE RIVER TO APALACHICOLA FL OUT TO 20 NM- COASTAL WATERS FROM SUWANNEE RIVER TO KEATON BEACH OUT 20 NM- WATERS FROM APALACHICOLA TO DESTIN FL FROM 20 TO 60 NM- WATERS FROM SUWANNEE RIVER TO APALACHICOLA FL FROM 20 TO 60 NM- 813 PM EDT SAT AUG 18 2012 /713 PM CDT SAT AUG 18 2012/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ALABAMA... SOUTHWEST AND SOUTH CENTRAL GEORGIA...AND THE FLORIDA BIG BEND AND PANHANDLE...AND ADJACENT COASTAL WATERS. .DAY ONE...TONIGHT... AN AREA OF RAIN WITH A FEW EMBEDDED THUNDERSTORMS IS EXPECTED TO MOVE INTO THE WESTERN PART OF THE FORECAST AREA TONIGHT AND GRADUALLY WEAKEN. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY... A CONVEYOR OF DEEP TROPICAL MOISTURE WILL BE PULLED NORTHEAST FROM HELENE OR ITS REMNANTS INTO THE LOCAL FORECAST AREA FROM LATE IN THE WEEKEND INTO THE MIDDLE OF NEXT WEEK. THIS WILL SET UP A PERIOD OF ELEVATED RAIN CHANCES WITH LOCALLY HEAVY RAIN AND FLOODING POSSIBLE. THERE WILL ALSO BE A SOMEWHAT ELEVATED THREAT FOR SEVERE WEATHER ON SUNDAY AND MONDAY AS THE JET STREAM DIPS UNUSUALLY FAR SOUTH FOR THIS TIME OF YEAR. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. FOR ADDITIONAL INFORMATION...VISIT THE NATIONAL WEATHER SERVICE WEBSITE ON THE INTERNET AT WEATHER.GOV...THEN CLICK ON YOUR AREA OF INTEREST ON THE NATIONAL MAP. DVD/WOOL
The national radar mosaic for the moment the first event began.
7 heavy rain. Local standard time, as filed.
The media relayed a report from a viewer of 6 inches of rainfall in Southport since August 19th.
The Perry co-op observer reported a 24 hour rainfall total of 3.32 inches ending at 2 pm EDT.
A 24 hour rainfall total of 3.02 inches was recorded at RAWS site PRWF1.
A 24 hour rainfall total of 3.79 inches was recorded by APRSWXNET site C8103 located on Saint George Island.
The broadcast media relayed a viewer report of 3.62 inches of rain since 10 am in Panacea.
The broadcast media relayed a viewer report of 4 inches of rain about 10 miles WSW of Perry.
The broadcast media relayed a viewer report of 3.75 inches of rain in Waukeenah.
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: 396970, 396969, 396971, 396972, 396973, 396974, 396975.