530
AWUS01 KWNH 270526
FFGMPD
FLZ000-GAZ000-TNZ000-ALZ000-270845-

Mesoscale Precipitation Discussion 1072
NWS Weather Prediction Center College Park MD
125 AM EDT Fri Sep 27 2024

Areas affected...northern FL into GA and far eastern AL

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

Valid 270522Z - 270845Z

Summary...Heavy rain from Helene`s inner core to track NNE across
GA through 08Z with an additional 3-5 inches through 09Z. Farther
west, an axis of heavy rain is likely to develop 06-08Z. Rainfall
rates of 1-2 in/hr will be common but localized rates near 3 in/hr
will be found with Helene`s eyewall.

Discussion...Hurricane Helene was located just north of the FL/GA
border, about 10 miles west of VLD, moving toward the NNE with an
average 3-hr speed of ~28 kt calculated via hourly NHC position
updates through 05Z. Radar imagery showed the heaviest rain
located in the northern eyewall, while rain was considerably
lighter in the southern semicircle of Helene`s inner core. A
second band of heavy rain was located northwest of the eyewall,
pivoting over ABY to just east of TLH with training from NNE to
SSW supporting increasing rainfall rates over the past hour. While
accurate ground truth is difficult to assess along the path of a
landfalling hurricane, MRMS-derived hourly rainfall has been
between 1-3 inches over the past 3 hours to the north of Helene
while waves of higher rainfall intensity have overspread central
to northwestern GA with rainfall rates occasionally peaking above
1 in/hr.

Helene is expected to maintain a similar forward speed and track
through 08Z with the core of the heaviest rain, associated with
Helene`s eyewall, tracking NNE across east-central GA. Rainfall
rates of 1-3 in/hr are likely but with 15-minute rates of 0.5 to 1
inch, leading to the rapid accumulation of water on the surface.
This will especially be true as this path will take some of
Helene`s highest rainfall rates across a stripe of 5-8 inches
which is estimated to have fallen in a stripe from near Dublin, GA
to just west of Augusta over the past 24 hours.

Farther west, low level convergence along an axis near or just
east of the AL/GA border is expected to enhance rainfall intensity
in the 07-09Z time frame. It is here where easterly winds of 30-50
kt in the 925-850 mb layer will meet and converge with northerly
to NNW winds over eastern AL. Mean steering flow oriented similar
to the expected axis of convergence will allow for rainfall rates
of 1-2 in/hr to develop later this morning, along with areas of
flash flooding where these higher rates overlap with heavy rain
which has fallen over the past 24-48 hours.

Otto

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...BMX...CAE...CHS...FFC...GSP...HUN...JAX...MRX...
OHX...TAE...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON   35428610 35328552 34728498 34258438 34158318
            33508200 32108176 31148206 30428267 30208366
            30498471 31228523 33048573 34658633