AWUS01 KWNH 300911
FFGMPD
FLZ000-GAZ000-301510-

Mesoscale Precipitation Discussion 1009
NWS Weather Prediction Center College Park MD
511 AM EDT Wed Aug 30 2023

Areas affected...Portions of the FL Panhandle....Big Bend of
FL...Southern GA

Concerning...Heavy rainfall...Flash flooding likely

Valid 300910Z - 301510Z

SUMMARY...Extremely dangerous Hurricane Idalia approaching the Big
Bend of FL. Landfall to occur in a few hours. Very heavy rainfall
arriving with the core of Idalia will likely lead to numerous
instances of flash flooding, some of which may be significant,
going through the morning hours.

DISCUSSION...GOES-E IR satellite imagery shows Hurricane Idalia
quickly approaching the Big Bend of FL as the storm advances
steadily across the northeast Gulf of Mexico. As of 5AM EDT, the
eye of Idalia was centered at 29.1N 84.1W, or about 60 miles west
of Cedar Key, FL and the storm was moving north-northeast at 18
mph.

Heavy rainfall associated with Idalia's Central Dense Overcast
(CDO) is overspreading eastern portions of the FL Panhandle and
the FL Big Bend region, with locally strong outer rainbands around
Idalia's eastern semicircle impacting the central and northern
portions of the FL Peninsula. Some of the rainfall rates within
these outer rainbands have been as high as 1.5 to 2 inches/hour.

The rainfall rates offshore with Idalia's CDO including its
eyewall have been steadily increasing, and over the last few
hours, the northern and western eyewall of Idalia has become quite
intense looking on radar as the hurricane continues to intensify,
and the rates within the eyewall are likely reaching 3 to 4
inches/hour.

These heavier rainfall rates associated with Idalia's eyewall will
begin arriving by 12Z (8AM EDT) as the storm prepares for landfall
and then begins moving inland. By 15Z (11AM EDT), the storm should
begin turning northeast while crossing into far southern GA as it
comes under influence of an upper trough moving into the Northeast
U.S.

Strengthening right-entrance region upper-jet dynamics and
increasing larger scale baroclinic forcing will allow the heavier
rains with Idalia to become increasingly concentrated around the
north side of the circulation later this morning. Eventually drier
air should begin to undercut the southern and eastern flanks of
the storm.

The 00Z HREF guidance shows very high probabilities (60% to 80%)
of 2+ inch/hour rates along and just to the left of Idalia's
track, with 3+ inch/hour rates (20% to 50%) showing up as well.
Expect areas near Tallahassee and east down toward Perry to get
into some of these extreme rainfall rates, with the axis then
extending north toward Moultrie and Valdosta in southwest GA by
mid to late morning.

Expect some additional rainfall totals for the time frame going
through 15Z (11AM EDT) to reach 3 to 6 inches with isolated
heavier amounts up to 8 inches. Numerous instances of flash
flooding, some of which may be significant, are expected as a
result this morning.

Orrison

ATTN...WFO...FFC...JAX...MLB...TAE...TBW...

ATTN...RFC...SERFC...NWC...

LAT...LON 31888264 31608188 31288160 30658160 29978178
29398185 28848189 28128221 28158278 28668287
29068303 29588344 29848414 29638478 29978518
30798492 31468428 31828348

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