981
FXUS62 KMLB 191130
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
730 AM EDT Thu Sep 19 2024

...New AVIATION...

.AVIATION...
(12Z TAFs)
Issued at 730 AM EDT Thu Sep 19 2024

Scattered showers and storms are forecast today, mainly after
20-21Z. The highest coverage looks to be inland from the Treasure
Coast, with VCTS included at affected terminals. A few storms
could produce gusty winds. Confidence in timing and location too
low to include TEMPOs at this time. Light offshore flow this
morning will veer onshore with the sea breeze, remaining around
10kts or less. Convection should diminish in the evening hours
(02-03Z). Winds once again light and variable overnight.

&&

.PREVIOUS DISCUSSION...
Issued at 358 AM EDT Thu Sep 19 2024

KEY MESSAGES:

- Shower and storm chances today will peak (40-70%) generally
  south of Orlando. From Friday through early next week, chances
  of rain will fall below normal.

- Minor coastal flooding remains possible, particularly during
  late morning high tides from Friday through the upcoming
  weekend. Low-lying streets, yards, and docks may flood along
  the barrier islands and Intracoastal.

- There is a medium chance (40%) for tropical development in the
  NW Caribbean or Southern Gulf of Mexico by next week. It is too
  early to determine what, if any, impacts for East Central
  Florida. However, continue to monitor the forecast for updates.

              ----------Synoptic Overview----------

A mid-level trough extends down the Eastern Seaboard to Florida this
morning with ridging over Texas. This pattern remains stagnant for
the rest of the week before a shortwave in the Desert Southwest is
forecast to push ridging eastward toward Florida by early next week.
At the surface, high pressure will settle into the Appalachians by
this weekend, with easterly boundary layer flow gradually resuming.

With the northerly-component mid-level flow, somewhat below normal
total moisture (PWATs) will be advected over Central Florida late
this week through early next week. Occasional perturbations in the
boundary layer may introduce transient increases in moisture. With
H85 T`s near normal, temperatures should hold close to seasonal
averages through early next week.

By the mid to latter portion of next week, the grand ensemble
indicates that the Central American Gyre is forecast to become more
active. Many members indicate deep tropical moisture will lift
northward toward the Gulf and perhaps even Florida. The National
Hurricane Center indicates a 40% chance of tropical development over
the next 7 days, potentially in the NW Caribbean or southern Gulf of
Mexico.

             -------Sensible Weather & Impacts-------

Today & Tonight...

Early this morning, we continue to monitor some remnant showers and
storms along the Treasure Coast. Once this activity pushes offshore,
it should be a fairly quiet morning. This afternoon, HREF members
and RAP guidance show that the juxtaposition of deeper moisture and
subtle convergence will generally lie south of Orlando. Storm
chances vary between 20-30% north of Orlando to 50-70% along much of
the Treasure Coast. Main threats include brief gusty winds of 35-45
mph, occasional lightning, and heavy rain leading to minor flooding.
Storms may linger after sunset across our southern counties before
diminishing overnight. Highs should range in the lower 90s with peak
heat indices from 98-103. Expect lows in the low/mid 70s.

Friday-Saturday...

Broad troughing persists over Florida along with lingering weak
vorticity at H5. Meanwhile, moisture values continue to decrease,
stymieing the potential for widespread showers and storms.
Northeasterly surface flow will develop, allowing for an
increasingly dominant Atlantic breeze each day. For now, we have
limited shower/storm chances to 20-30% from Melbourne north and 30-
40% Treasure Coast on Friday. Afterward, only 20-30% shower/storm
chances return on Saturday. Highs will reach the upper 80s to around
90F.

High astronomical tides and onshore flow will introduce the threat
of minor coastal flooding at high tide, particularly with the late
morning high tide cycles each day. The Coastal Flood Advisory has
been extended to include Saturday, and may eventually need to be
extended to Sunday.

Sunday-Tuesday...

Ridging overtakes Florida aloft and surface high pressure remains to
our north, keeping easterly boundary-layer flow in place. With
continued below-normal available moisture, rain/storm chances will
remain muted at 20-30%. Highs continue to range from the upper 80s
to around 90 with lows in the low 70s inland and mid/upper 70s along
the coast. Wave guidance shows increasing swells late this weekend
which could make surf conditions hazardous for beach-goers.

Mid/late next week...

Confidence is quite low as we move deeper into next week. The latest
(19/00z) grand ensemble suite continues to indicate the Central
American Gyre (CAG) will consolidate waves of convection and deep
moisture in the NW Caribbean. In the mid-latitudes, the ensembles
also indicate substantial spread in the depth and speed of movement
of a trough riding atop a flat and weakening ridge axis extending
from Texas to Florida . Therefore, the guidance is split on where
this disturbance will be drawn and exactly when. At a bare
minimum, that has local implications on when rain and storm
chances increase.

There is currently a medium (40%) potential for tropical development
in the NW Caribbean or So. Gulf, near or within the developing CAG,
over the next 7 days. The timing and depth of the aforementioned
mid-latitude trough appears to be critical in the movement of any
tropical feature, if one were to develop. There is much
speculation regarding whether a tropical cyclone will form, and if
so, where it will ultimately go. Presently, the guidance shows a
wide gamut of potential outcomes. Ultimately, the impacts on our
area are unclear at this time - but it`s yet another reminder: we
are now in the heart of hurricane season. Let`s take this
opportunity to go over our hurricane preparation kits and plans.

&&

.MARINE...
Issued at 358 AM EDT Thu Sep 19 2024

Today-Tonight... Lingering showers/storms over the Treasure Coast
waters are expected to weaken this morning. Generally 3-4 FT seas
today with winds becoming NE 5-12 KT north of Sebastian Inlet and
more variable to the south. Scattered showers and storms are
forecast today especially south of Cape Canaveral. Some of the
storms could be offshore-moving and gusty.

Friday-Monday... 2-4 FT seas persist through at least Saturday
before building to 3-5 FT from Sunday into Monday as northeast
onshore winds increase to 8-15 KT and a northeast swell enters the
local Atlantic. Shower and thunderstorm activity will be more
isolated.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  89  73  88  74 /  20  10  20  10
MCO  92  74  90  73 /  40  20  20   0
MLB  90  74  88  74 /  40  30  30  10
VRB  90  73  88  73 /  50  50  40  20
LEE  90  73  90  73 /  30  10  10   0
SFB  90  73  89  72 /  40  10  20   0
ORL  92  75  90  74 /  40  10  20   0
FPR  90  73  88  72 /  60  50  40  20

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 2 PM EDT Saturday for FLZ141-154-
     159-164-347-447-647-747.

AM...None.
&&

$$

DISCUSSION...Heil
AVIATION...Leahy