Deep moisture was increasing from the south ahead of Hurricane Idalia. This moisture combined with diurnal instability and the sea breezes produced locally heavy rainfall near boundary mergers.
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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.
Deep moisture was increasing from the south ahead of Hurricane Idalia. This moisture combined with diurnal instability and the sea breezes produced locally heavy rainfall near boundary mergers.
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 28, 6:41 AM EST, 4 hours 19 minutes earlier.
Area Forecast Discussion
National Weather Service Jacksonville FL
741 AM EDT Mon Aug 28 2023
...New AVIATION...
.UPDATE...
Issued at 543 AM EDT Mon Aug 28 2023
Hurricane watches have been posted for inland locations west of
U.S. Highway 301 in north and north central FL. The National
Hurricane Center has increased the forecast intensity of Tropical
Cyclone Idalia, with an expected peak at Major Hurricane intensity
(Category 3) on Tuesday night as Idalia parallels the west central
FL coast and accelerates northeastward towards the FL Big Bend
and Nature Coasts during the predawn hours. Based on the latest
official forecast from the National Hurricane Center, tropical
storm force winds are expected to move towards the Interstate 75
corridor in north central FL after midnight on Tuesday night.
Sustained hurricane force winds are expected to impact the
Suwannee Valley after sunrise on Wednesday, with these winds
potentially impacting the Interstate 10 corridor (likely west of
metro Jacksonville) during the late morning hours on Wednesday.
Additional hurricane, tropical storm, and storm surge watches are
likely to be issued for southeast GA, northeast and north central
FL later this morning and afternoon.
&&
.NEAR TERM (Through Tonight)...
Issued at 306 AM EDT Mon Aug 28 2023
Clear to partly cloudy skies are expected Today
across the forecast area with upper ridging building just E of FL.
Onshore flow will allow sea breeze to move well inland, with
widely scattered showers possible along it as it moves inland,
possibly isolated t-storms over sctrl FL by mid-late afternoon.
Another hot day expected with low-mid 90s for max temperatures,
and low temperatures Tonight in the mid 70s.
&&
.SHORT TERM [Tuesday through Wednesday Night]...
Issued at 306 AM EDT Mon Aug 28 2023
Focus is on TC Idalia during this period. Idalia is presently
stalled east of the Yucatan Peninsula of Mexico, but latest
guidance is converging on solution with TC tracking slowly due
northward into SE Gulf of Mexico later Today, then moving a little
faster N to NNE toward Big Bend region Tuesday, making landfall
Tuesday night along coast SW of Suwannee Co, and tracking more NE
into s-ctrl GA Wednesday. This hurricane track will yield
significant impacts in our forecast area, most substantial in
terms of wind and rain across the Suwannee River Valley of nrn FL
into s-ctrl GA. Rainfall amounts of 2-4 inches expected in much of
our CWA, with a potential swath of 4-8 inches with locally higher
amounts across the Suwannee River Valley Region of northern FL
into s-ctrl GA. Despite prior dry conditions, this amount of rain
could support a flood threat especially in areas with poor
drainage. There will also be a risk of isolated tornadoes, with
the best potential for the needed overlap of sufficient
instability and strong shear being over our wrn FL counties.
Instability is the big question mark given that widespread rain
will move in early Wed and help keep temperatures down.
Prior to the storm on Tuesday, heating of moist environment is
expected to generate numerous showers and a few t-storms across
the forecast area, with consensus guidance suggesting high POPs.
Expecting high temperatures to be in the 90-95 range across the
forecast area.
Temperatures will be suppressed into the upper 70s to around 80
during much of Wednesday due to precipitation with Idalia. Latest
guidance suggests impacts will shift NE of the area late in the
day Wed, with improving conditions from SW to NE during the
afternoon, potentially allowing some temperature rebound into the
mid 80s late in the day across nrn FL.
Note that the ZFP and CWF products will be delayed due to the
likelihood of inland watch/warning products from the upcoming 5am
NHC package.
&&
.LONG TERM [Thursday through Sunday]...
Issued at 306 AM EDT Mon Aug 28 2023
After the passage of Idalia, the upper pattern shifts to show
development of a large upper ridge over the area. A surface area
of high pressure will build north of the forecast area,
maintaining an onshore flow pattern during this period. Higher
rain chances Thu/Fri will decrease during the Weekend as the ridge
builds over the area. Latest consensus guidance suggests near
normal temperatures during this period.
&&
.AVIATION...
(12Z TAFS)
Issued at 740 AM EDT Mon Aug 28 2023
VFR conditions expected to across the TAF sites, with the
lingering BR dissipating from VQQ/GNV this morning. With the
Atlantic sea breeze expected to start moving through around 14Z,
VCSH expected along TAF sites along the sea breeze passage from
14Z to 18Z. Easterly winds expected during the TAF period.
&&
.MARINE...
Issued at 306 AM EDT Mon Aug 28 2023
A stalled front will remain NW of waters through midweek while
Tropical Storm Idalia strengthens and moves northward into the
eastern Gulf of Mexico. Meanwhile, swells from distant Hurricane
Franklin will reach the local waters later Today through mid week,
resulting in building seas prior to impacts from Idalia are
realized.
Wind and rain impacts from Idalia will increase Tuesday night
and Wednesday, with potential for sustained Tropical Storm
conditions, waterspouts and rough seas. Winds will shift to an
offshore direction late Wednesday and Thursday as this tropical
cyclone moves northeastward away from the waters.
High pressure will build from the north northwest late in the week,
into the weekend.
Rip Currents: SE GA Moderate Risk Today, High Risk Tuesday
NE FL High Risk Today and Tuesday
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 94 75 92 74 / 20 10 80 80
SSI 91 80 91 78 / 20 20 80 90
JAX 93 77 94 77 / 20 10 80 80
SGJ 90 77 92 77 / 20 10 90 80
GNV 94 75 93 75 / 30 30 90 80
OCF 95 75 94 77 / 40 30 90 80
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Hurricane Watch for FLZ020-021-023-030-031-035-122-136-222-236-
240-340.
High Rip Current Risk through this evening for FLZ124-125-133-
138.
GA...None.
AM...None.
&&The national radar mosaic for the moment the first event began.
1 heavy rain. Local standard time, as filed.
A mesonet station at the St. Johns County EOC measured 4.9 inches as thunderstorms trained over the area during the late morning through early afternoon hours. The time frame was estimated.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Florida in 2023Every state in 2023This day in weather historyWarnings in Florida, August 2023
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: 1125220.