AWUS01 KWNH 070313
FFGMPD
FLZ000-070900-

Mesoscale Precipitation Discussion 1092
NWS Weather Prediction Center College Park MD
1113 PM EDT Sun Oct 06 2024

Areas affected...Southern Peninsular Florida and the Upper Keys...

Concerning...Heavy rainfall...Flash flooding possible

Valid 070315Z - 070900Z

SUMMARY...Approaching surface frontal wave with bands of warm
advective tropical showers/thunderstorms capable of 2-2.5"/hr
rates and spots of 3-5" totals along the coasts may pose localized
urban rapid inundation flooding through overnight hours.

DISCUSSION...GOES-E 3.9um SWIR depicts a few boundary layer swirls
of Cu and TCu across the eastern Gulf of Mexico (main one near
25.8N 85.5W) with the frontal/convergence boundary extending
eastward to just offshore of S Sarasota county before paralleling
the SW Coast through the central Keys.  VWP and RADAR mosaic
suggests a 925-850mb wave in proximity of Naples, pressing
eastward.  This is spurring an increase in low level southwesterly
flow and warm advection from the Florida Channel and enhancing
convergence with new deepening convection through the central Keys
starting to arch northeastward.  Relative maxima in low level
instability and available moisture along/ahead of this band are
running about 2000-2500 J/kg SBCAPE and 1.05-1.25" per CIRA LPW
values.  This will allow for solid low level moisture loading for
intense tropical rain showers and be capable of an easy 2-3"/hr
rain rate, but translation/duration will be critical to pose
flooding problems.

As the aforementioned wave crosses southern FL, WAA and
southwesterly flow is expected to lift north and replace the band.
Deeper layer (700-500mb) flow appears to suggest weak ridging to
delay or allow the wave to pivot across the Everglades while the
band lifts north.  This will bring stronger cells along/through
areas of Miami-Dade with those high rates through the next few
hours.  There is potential the band will slow and increase
duration near the pivoting wave over the urban corridor and
present increasing duration of heavier rainfall totals with 3-5".=20
HREF probability of 40-80% of 3" and 30-50% of 5" remains across
the southern tip and up the east coast to Palm Beach county.=20=20
Given a  secondary boundary/theta-e gradient is also connected to
a prior wave/WAA exists resulting in localized frictional
convergence across Broward county lifting north potentially adding
to/expanding the risk area of potential 3-5" totals by 09z.  Given
proximity to urban/flat and some already saturated areas, rapid
inundation flooding may occur locally with these cells through the
overnight period and is considered possible.

Along the SW FL coast...
The potential for excessive rainfall/higher totals, is diminished
slightly compared to the SE FL coast as cells are more likely to
reside along/just offshore through the overnight period.  However,
there remains solid convergence along the southeast angled frontal
zone to support similar cells from Manatee to Lee/Charlotte county
and with limited cell motions, so though the cells are likely to
remain just offshore, there remains some potential for 2-2.5"/hr
rates but could result in slightly higher overall totals if they
sneak ashore.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9_7cGQdvrEw7ej5aqDEy8Z5IxL-XzFWS6mFU4daM6-UoumjKkf6Lm_uXSparPF6aTtcP=
87H0kDMJREFSlW_QoFuAcN4$  for graphic product...

ATTN...WFO...KEY...MFL...MLB...TBW...

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

LAT...LON   27228016 26577992 25867999 25218020 24738081=20
            24798129 25718143 25828178 26208193 26538231=20
            26988253 27178260 27198225 26408162 26028113=20
            26028075 26568050 27178040=20

=3D =3D =3D
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