AWUS01 KWNH 121216
FFGMPD
FLZ000-121800-

Mesoscale Precipitation Discussion 0427
NWS Weather Prediction Center College Park MD
815 AM EDT Wed Jun 12 2024

Areas affected...western (Gulf) coast of central and southern FL

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

Valid 121215Z - 121800Z

Summary...Localized rainfall rates on the order of 2-4"/hr may
support additional localized totals of 6"+ with sufficient
training/repeating of cells. Localized instances of flash flooding
are likely, given the increased sensitivity from recent heavy
rainfall.

Discussion...Heavy shower activity is once again building over the
warm waters of the southeast Gulf of Mexico, following a relative
lull this morning in convective activity along the western coast
of central FL. A 25-35 kt low-level jet (LLJ) is situated just
downstream (with the maxima near the eastern central coast of FL),
resulting in a localized enhancement of lift (via DPVA with
minimal influence from upper-level dynamics). The mesoscale
environment is reminiscent of the tropics, as PWATs of 2.0-2.5"
are near record levels (per TBW sounding climatology) with dew
points in the upper 70s to near 80deg F, ML CAPE of 1000-1500
J/kg, and effective bulk shear near 20 kts. While deep convection
may be able to tap into more significant instability (as indicated
by 3000-5000 MU CAPE just offshore), relatively shallow heavy showers/thunderstorms will easily produce 1-2"/hr rates (with more
intense convection capable of 2-4"/hr rates, particularly if
additional training/repeating occurs).

Hi-res CAMs paint a rather concerning picture this morning,
suggesting additional localized totals of 6"+ are possible through
18z. This is indicated by both the 06z HREF probability matched
mean (PMM) QPF and 40-km neighborhood exceedance probabilities
(40-70% for 5" exceedance), as well as by hourly runs of the HRRR
since 06z. That said, not every HREF member or every run of the
HRRR indicates such totals, as this threat is conditionally
dependent on a training/repeating axis to set up along the coast.
This could occur anywhere from Sarasota to Naples, though the Fort
Myers/Punta Gorda region looks most favored (per the observational
trends matching up quite well with guidance). Given that average
totals over the past 24 hours commonly range from 3-5" (with
localized totals remarkably as high as 6-12", per MRMS
esitimates), isolated instances of flash flooding appear to be
likely (with locally significant impacts possible in poor
drainage, urbanized terrain).

Churchill

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

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

LAT...LON 28188232 27958105 26628083 25558114 25978226
27288306 27968304
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AWUS01 KWNH 130936
FFGMPD
FLZ000-131535-

Mesoscale Precipitation Discussion 0430
NWS Weather Prediction Center College Park MD
536 AM EDT Thu Jun 13 2024

Areas affected...south-central FL Peninsula

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

Valid 130935Z - 131535Z

SUMMARY...Locally heavy rainfall is expected over portions of the
south-central FL Peninsula through 15Z. While the coverage of
heavy rainfall is not expected to be widespread, flash flooding
from rainfall rates of over 1 inch in 15 minutes and/or over 3
in/hr will be possible.

DISCUSSION...Local radar imagery from KTBW and GOES East infrared
satellite imagery showed locally heavy rain occurring via warm
topped showers in the vicinity of Tampa Bay at 09Z. These showers
were focused ahead of a weak mesolow to the southwest of SRQ,
steadily approaching the coast where uninhibited instability of
~1500 J/kg MLCAPE was present via the 09Z SPC mesoanalysis.
Convective inhibition increased with inland extent from the Sun
Coast, especially to the north and south which may act to inhibit
farther spreading of heavy rainfall activity in the short term.

A tropical airmass was in place over central to southern FL with
precipitable water values that ranged from 1.8 inches near Tampa
Bay to 2.5 inches over the FL Keys (per satellite derived TPW
imagery). Due to the dominance of warm rain processes, efficient
rainfall production will be capable of high rainfall rates with
1-2 in/hr likely but even greater subhourly rates rainfall of 1+
inches in 15 minutes possible. As the mesolow continues toward the
NE, a short term flash flood threat will exist with increasing
showers and locally intense rainfall rates.

Farther south, an increase in showers and thunderstorms is
expected to occur later this morning, to the southwest of a
broader 850 mb low estimated to be near 30N 80W via LPW imagery.
An axis of low level convergence (which extends up through 850 mb)
was located south of the broader cyclonic circulation east of the
northern FL Peninsula into the eastern Gulf of Mexico. This low
level convergence axis, aided by increasing 825 mb winds per RAP
forecasts, is likely to become a focus for the development of
locally heavy rain into the mid-morning hours, beginning between
11-13Z with increased surface heating. Rainfall rates of 1-2 in/hr
but with subhourly rainfall of 1+ inches in 15 minutes will be
possible atop very wet antecedent conditions due to 4 to 10+
inches of rain which impacted the south-central FL Peninsula over
the past 48 hours.

Otto

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

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

LAT...LON 28298069 27998035 27608014 26897988 26558023
26038140 26108212 26628252 27318301 27768301
28028283 28128232 28168174
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AWUS01 KWNH 041815
FFGMPD
FLZ000-050013-

Mesoscale Precipitation Discussion 0802
NWS Weather Prediction Center College Park MD
215 PM EDT Sun Aug 04 2024

Areas affected...western Florida Peninsula

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

Valid 041813Z - 050013Z

Summary...Tropical Storm Debby continues to organize and spread
robust convection into the western Florida Panhandle. Flash flood
potential continues.

Discussion...Debby has exhibited strengthening across the eastern
Gulf of Mexico today. Additionally, a fetch of robust convection
within its eastern semicircle has expanded eastward to cover much
of the Florida Peninsula roughly from Gainesville south through
Naples and the western Keys. Several areas of 2-4 inch rainfall
totals have been observed, with the highest totals occurring from
Naples north to Fort Myers and Punta Gorda. Radar mosaic imagery
depicts many embedded convective elements streaming northward/north-northwestward within the overall fetch of
convection, promoting areas of 1-2 inch/hr rain rates (locally
higher) at times.

The ongoing scenario is expected to continue through the evening
and beyond. Not only is the dominant convective band (located
from near Tampa to Naples) continuing to be maintained with an
abundantly moist/unstable airmass, but additional strong
convection located within confluent low-level flow extending from
the Keys to roughly 70 miles west of Fort Myers will likely stream
into the region from the south and west. Areas of 1-2 inch/hr
rain rates are likely to continue, and another 2-4 inches of
rainfall can be expected across much of the discussion area.
Locally higher amounts remain possible where convective banding is
most focused and somewhat stationary through 00Z.

Cook

ATTN...WFO...JAX...MFL...MLB...TAE...TBW...

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

LAT...LON 29928372 29858284 29178181 28018121 26798079
25688090 25378122 25818167 26468218 27048239
27518266 27838283 28498273 28928291 29378328

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AWUS01 KWNH 041108
FFGMPD
FLZ000-GAZ000-041707-

Mesoscale Precipitation Discussion 0973
NWS Weather Prediction Center College Park MD
708 AM EDT Wed Sep 04 2024

Areas affected...northeastern Florida

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

Valid 041107Z - 041707Z

Summary...A few rounds of locally heavy rainfall are expected in
northeastern Florida near the Jacksonville Metro area. Isolated
instances of flash flooding are possible through at least 17Z/1p
EDT today.

Discussion...Latest radar mosaic imagery depicts a band of
convection extending from near Jacksonville, FL east-northeastward
to open Gulf Stream waters near 31.3N, -79.6W. This band of
convection was collocated with a surface front very near the
region, with focused convergence, appreciable instability (1500
J/kg MLCAPE), and high PW/moisture content (2.3 inch PW)
supporting deep convection with appreciable rainfall rates.
Steering flow aloft was weak, allowing cells to migrate slowly west/west-southwestward amid 20-kt easterly 850mb flow. This
regime was promoting slow movement and training of cells into the
Jacksonville Metro area, where MRMS and gauge estimates of 1-5
inch rainfall totals have been noted in a few spots over the past
12 hours.

The ongoing regime is expected to continue most of the day today,
with Gulf Stream convection migrating west-southwestward toward
northeastern Florida. Given the rates and potential for
persistence of rainfall/multiple rounds of cells, a few spots of
3-5 inch rainfall totals cannot completely be ruled out through
17Z. Some of this rainfall could occur over Jacksonville Metro
and pose at least localized issues with excessive runoff/flash
flooding.

Cook

ATTN...WFO...JAX...MLB...

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

LAT...LON 30858155 30618094 30128066 29728067 29358096
29338181 29678273 30348265 30708214
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AWUS01 KWNH 092331
FFGMPD
FLZ000-100445-

Mesoscale Precipitation Discussion 1100
NWS Weather Prediction Center College Park MD
730 PM EDT Wed Oct 09 2024

Areas affected...north-central FL Peninsula

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

Valid 092328Z - 100445Z

SUMMARY...An axis of extreme rainfall, stretching from the Tampa
metropolitan region northeastward into the north-central FL
Peninsula, is expected to result in major to locally catastrophic
flash flooding with considerable threats to life and property.
6-hr rainfall totals of at least 5-8 inches with hourly rainfall
in the 2-3 in/hr range are expected.

DISCUSSION...The 23Z update from NHC placed the center of
Hurricane Milton 35 miles WSW of Sarasota, FL. Local radar imagery
at 23Z from KTBW showed the heaviest rain located within what is
effectively the northern eyewall which has pushed ashore and arced
from Manatee into southern Hillsborough and much of Pinellas
counties with MRMS and gauge data showing 1-2 in/hr rainfall
rates. Portions of St. Petersburg to Bradenton have already picked
up 5-8 inches of rain since midnight and flash flooding is
ongoing. Farther east, an outer rain band had largely moved
offshore of the eastern Peninsula but was arcing northwestward
ashore just north of Cape Canaveral with 4-8 inches already
reported across Brevard County.

An axis of strong low level convergence tied to the northern
eyewall, extending northeast from the center of Milton to Volusia
County (just north of the forecast track of Milton) will support a
prolonged period of high rainfall rates, 1-2 in/hr but locally in
the 2 to 3+ in/hr range, with the axis training from WSW to ENE
and slowly lifting north with time. Some locations could
experience rainfall rates in excess of 1 in/hr for 2-4 hours,
causing rapid rises of water above the surface as water will not
have sufficient time to drain, especially across the mostly
impervious surfaces of the St. Petersburg into the Tampa metro and
possibly nearing Orlando later tonight. Additional rainfall of at
least 5-8 inches is expected from St. Petersburg, northeastward
into the central Peninsula where the WoFS has consistently painted
high probabilities of exceeding 5 inches of rainfall. The 22Z WoFS
cycle indicated 50 to 90 percent probabilities of 5+ inches and
90th percentile (reasonable worse case scenario) values of 7-10
inches. Major to locally catastrophic flash flooding is expected
as a result of these high rainfall rates.

Otto

ATTN...WFO...JAX...MLB...TBW...

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

LAT...LON 29888111 29688103 28598054 28528063 28238143
27798205 27438295 27898313 28898262 29318212
29678163
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