A stalled weak front extending across inland SE GA with a mid/upper level short wave trough moving over the boundary in the afternoon. 25 inches.
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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.
A stalled weak front extending across inland SE GA with a mid/upper level short wave trough moving over the boundary in the afternoon. Southerly steering over a very moisture airmass with PWATs near 2.25 inches. The combination of the high moisture, weak SSW steering flow and lift under the passing upper level wave triggered locally heavy rainfall and gusty downdraft winds in sea breeze collisions storms toward the Atlantic coast.
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 Sep 25, 8:25 PM EST, 3 hours 35 minutes earlier.
Area Forecast Discussion National Weather Service Jacksonville FL 925 PM EDT Fri Sep 25 2020 ...AREAS OF DENSE FOG POSSIBLE INLAND EARLY ON SATURDAY MORNING... ...HOT AND HUMID THIS WEEKEND WITH INCREASING THUNDERSTORM CHANCES ON SUNDAY AFTERNOON... .UPDATE... Late evening surface analysis depicts weak low pressure over the Carolinas, with a weakening frontal boundary extending southwest of this feature across inland southeast GA and the FL Big Bend region. Aloft...a progressive shortwave trough was exiting the Appalachians and was moving northeastward into the Mid-Atlantic states. Deep-layered ridging has been displaced eastward over the Bahamas and eastern Cuba, while a cutoff trough was spinning over the upper Texas coast. Latest GOES-East derived Total Precipitable Water Vapor imagery indicates a much drier air mass in the wake of the frontal boundary to the west of the Altamaha/Ocmulgee Rivers, while a moist air mass persists across our area, with PWATS mostly in the 1.8 - 2 inch range. Despite increasing moisture levels and 0-6 km southwesterly speed shear around 30-35 knots, forcing from the shortwave trough well to the north of our region was only able to develop scattered convection across inland southeast GA this afternoon and evening. Activity is moving quickly northeastward and is crossing the U.S. Highway 301 corridor near Jesup, with isolated activity located along the FL/GA border to the west of Trail Ridge and also along the Altamaha River near Hazlehurst. Mid-level cloudiness is otherwise increasing in coverage along the U.S.-301 corridor in northeast FL, where a remnant Atlantic sea breeze boundary was drifting westward. Warm and humid conditions prevail area-wide, with temperatures outside of rain cooled locations still in the upper 70s to lower 80s at 01Z, with dewpoints uniformly in the low to mid 70s. Widely scattered showers will be possible through around midnight as activity collides with the remnant Atlantic sea breeze boundary positioned near U.S. 301. Abundant moisture and decreasing boundary layer winds should set the stage for widespread fog at inland locations early on Saturday morning, with areas of dense fog possible for locations west of U.S. Highway 301. Lows tonight will range from near 70 across inland southeast GA to the mid and upper 70s at coastal locations. Fog should dissipate before the mid-morning hours on Saturday. Heights aloft will rise as deep-layered ridging retrogrades westward from the Bahamas across the FL peninsula into the southeast Gulf of Mexico as shortwave troughing departs the Mid- Atlantic coast. Strengthening subsidence should result in only isolated late afternoon convection developing along the inland moving Atlantic sea breeze boundary for locations in the southern St. Johns River basin and the Ocala National Forest. Hot and humid conditions will prevail nearly area-wide as the frontal boundary dissipates, with highs ranging from the upper 80s to the lower 90s, with afternoon heat index values soaring to the 100-105 degree range. && .MARINE... A weakening frontal boundary will stall to the west of our local waters and will then dissipate during the weekend. A southerly evening wind surge around 15 knots will diminish after midnight. Seas of 3-5 feet tonight will fall back to 2-3 feet near shore on Saturday and then 2-3 feet throughout our waters from Saturday night through Monday. A weak pressure pattern will also prevail through Monday, resulting in prevailing light onshore winds beginning on Saturday afternoon as the Atlantic sea breeze boundary moves inland. Coverage of showers and thunderstorms will increase over our waters beginning on Sunday afternoon. A strong cold front will then approach our local waters on Tuesday night, creating increasing southwesterly winds. This front is slated to cross our local waters on Wednesday, accompanied by showers and thunderstorms. Rip Currents: Onshore winds developing towards noon on Saturday will combine with a lingering long period east southeast ocean swell to keep a moderate risk in place at all area beaches. && .HYDROLOGY... Tide levels continue to slowly diminish, with levels expected to reach near minor flood levels within the southern St. Johns Basin during times of high tide this weekend. We have cancelled the Coastal Flood Advisory and placed a Coastal Flood Statement for Putnam County through Saturday night, where mostly nuisance flooding is possible around times of high tide. && .PREV DISCUSSION [756 PM EDT]... .Near Term.../through Saturday/... As eastward tracking low pressure moves toward the Carolinas Tonight, a cold front will move into forecast area from the northwest. Scattered to numerous storms, with a few strong storms possible through this evening across SE GA as this front approaches. The front will move to near the FL/GA line Saturday, and stall, with isolated to scattered convection initiating across area during the heat of the day. Temperatures will trend well above normal this period. .Short Term.../Saturday night through Tuesday/... The frontal boundary will dissipate over region Sunday into Sunday night, as high pressure builds to the east northeast. With the high to the east northeast, a more moist onshore flow will yield increasing precipitation chances. The high will continue to the east northeast Monday into Monday night, as a cold front approaches from the west. The flow will become more from the south Monday into Monday night with moisture on the increase, yielding greater precipitation chances. A strong cold front will move southeast toward western counties Tuesday afternoon. Given the strength of this front, strong to severe storms will be possible with the frontal approach, especially during diurnal heating Tuesday afternoon into evening. Temperatures will continue above normal this period. .Long Term.../Tuesday night through Friday/... The ECMWF is a little slower than the GFS this period with the cold front sweeping through in the Tuesday night to Wednesday morning timeframe. The front is expected to move into southern FL for Thursday into Friday. Strong high pressure will build from the northwest Friday, which could lead to a period of enhanced onshore flow. Temperatures will trend near to below normal this period. A noticeable difference in airmass is expected later this period, as much drier air advects in following front, with dewpoints in the 50s common by late week. .AVIATION... [Through 00Z Sunday] VFR conditions will prevail through at least 05Z. Isolated showers may impact the regional terminals through around 05Z, but expected low coverage allowed for only vicinity coverage in the latest TAFs. Fog will likely develop at the inland terminals after 06Z, with dense fog and LIFR conditions possible at GNV and VQQ after 08Z. Fog and MVFR conditions will be possible elsewhere after 09Z, except at SSI and SGJ, where VFR conditions should prevail. VFR conditions should then prevail area-wide by 14Z. Light north- northwesterly surface winds will develop by 14Z at the terminals, followed by the Atlantic sea breeze pushing across the coastal terminals towards 16Z and then moving inland across the rest of the Duval County terminals by 21Z. Surface winds will shift to northeasterly and then easterly on Saturday afternoon, with sustained speeds at the coastal terminals increasing to near 10 knots by 17Z. && .PRELIMINARY POINT TEMPS/POPS... AMG 70 88 70 87 70 / 30 10 10 70 40 SSI 76 87 75 85 74 / 10 10 10 60 40 JAX 74 92 73 89 73 / 20 10 10 70 30 SGJ 77 89 76 88 74 / 10 10 20 50 30 GNV 73 92 71 89 72 / 20 10 10 80 20 OCF 73 92 72 90 73 / 10 20 10 70 20 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&
The Jacksonville radar (KJAX), 118 km away, was scanning. The volume nearest the first event began at 04:59 UTC.
3 heavy rain, 1 flood, 1 thunderstorm wind. Local standard time, as filed.
A total of 6 inches of rainfall was measured at in Hershel King Park over the weekend.
The St. Augustine airport AWOS measured 2.80 inches within 3 hours.
A mesonet station near Fruit Cove measured 3.45 inches of rain in 3 hours.
At 1625, a trained storm spotter reported heavy rain caused street flooding up to 1 ft deep in some areas in the vicinity of St. Augustine. Roads impacted by flood water included State Road 312, State Road 207 and US Route 1. Cars were stalled in flood water. At 1730, Emergency Management reported roads were closed in St. Augustine due to flood water. Road closures included San Sebastian Bridge and King Street from Ponce de Leon Blvd to past Whitney Street.
An oak tree was blown down across the road. There was a lot of heavy rainfall and saturated ground in the area. The cost of damage was estimated for Storm Data.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2020Every state in 2020This day in weather historyWarnings in Florida, September 2020
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: 921739, 921736, 921737, 921735, 921738.