891
FXUS62 KMLB 140800
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
400 AM EDT Tue May 14 2024

...New DISCUSSION, AVIATION, MARINE, FIRE WEATHER...

.DISCUSSION...
Issued at 400 AM EDT Tue May 14 2024

Key Messages:

-Continued chances for storms through midweek. A few of the
 storms could be strong to severe, with the primary hazards being
 gusty winds and large hail.

-Trending drier into late week, with hot conditions expected to
 return area-wide.

-Rain chances rise into the weekend, but unseasonably hot and
 humid conditions continue.

Short-Term Synoptic Overview:

RAP streamline analysis initialized a remnant mesolow/MCV feature
just offshore of Savannah, GA - associated with earlier convection.
A low-level jet segment extends from that feature down toward the
Space Coast, but it is moving offshore. Shortwave ridging will
quickly race across the state early today ahead of additional
subtropical jetstream energy currently along the N Gulf Coast. The
parent trough resides across the Red River Valley. Ahead of it,
another mesoscale perturbation is expected to move across North
Florida late this morning. The main trough axis will then move
toward the Tennessee Valley tonight, and an additional impulse is
progged to cross the state either late tonight or Wednesday. All of
this is sliding just north of a very warm, deep-layer ridge (+2 to
+3 sigma at H5) centered near the Cayman Islands.

Through at least the next 36 HR, many kinematic and thermodynamic
values will be within rare territory for May, suggesting (but not
guaranteeing) that severe weather continues to be a risk. H5 & H7
wind speed amplitudes will exceed the 90th percentile of
climatology, and ensemble members indicate a low-level jet tonight
at H85 which also could exceed the 90th percentile. In addition, a
ribbon of mean integrated WV Transport (IVT) values exceeding the
99th percentile, and closing in on the maximum of the CFSR model
climate, is forecast to move from N FL this afternoon to Central FL
by Wednesday evening. This will be in concert with an approaching
and weakening cold front sliding southward. ECMWF EFIs for CAPE-
Shear (13/12Z) exceed 0.9 through Wednesday, signifying a very
unusual convective parameter space for mid-May over much of Florida.
Finally, boundary layer temperatures will also exceed the 90th
percentile, causing some heat impacts.

Sensible Weather & Impacts:

Today...

As you can probably tell from the overview, this is a very complex
weather scenario for our area... posing multiple forecast
challenges. The first wrinkle has already occurred tonight, as the
MCV feature to our north caused a few gusts to around 40 MPH along
the Cape. This wind energy is now pushing out to sea as shortwave
ridging quickly traverses the state. Looking upstream, another well-
defined MCS with embedded strong storms is pushing into the FL
Panhandle and NE Gulf. A weak warm front is pushing north this
morning ahead of this feature, evidenced by winds veering from SE to
S. This band of storms will continue moving eastward, with HREF
members indicating areas near/north of Orlando to Titusville having
the highest chance (40-60%) for late morning & early afternoon
storms as the line approaches and likely begins to weaken. Some of
these storms could contain gusty winds to 50-60 MPH and coin-sized
hail. There is also a low, but non-zero, chance of a tornado in the
line. SPC places a Slight severe risk (level 2 of 5) along and north
of central Osceola Co to Cape Canaveral today and tonight. Closer to
the mid-level ridge, a pronounced cap (H7 T`s ~ +12C) is forecast to
exist south of this area, lessening the chances for storms through
mid-afternoon over the southern Space & Treasure Coasts.

Working conceptually, it would seem that a period of subsidence will
follow the morning disturbance, leading to somewhat limited storm
chances through the mid-late afternoon. Breezy southwest winds will
feed very warm air northward, so areas that remain rain-free will
become unseasonably hot. From Orlando southward, we are forecasting
widespread mid 90s and maximum heat indices from 100 to 105F. Vero
Beach and Ft Pierce could get very close to their daily records
(95F).

Uncertainty only grows from there. By late afternoon/early evening,
a pinned sea breeze should form, especially from Cape Canaveral
southward. Similar to yesterday, a few storms could develop on the
sea breeze convergence zone, where broad southwest flow meets
southeast winds off the Atlantic. Due to the aforementioned
parameter space, if storms do manage to pop on the sea breeze they
could quickly go severe with gusty winds, large hail, and a tornado
or two possible. Admittedly, this is a low-confidence forecast that
has potentially high impacts along our urbanized coastal corridor.
The SPC reflects this with a Marginal Risk for severe storms along
the Space and Treasure Coasts. Our storm chances along the coast
this evening range from 40-50%.

Tonight...

As the main trough enters the Tennessee Valley, the theta-E gradient
and baroclinic zone will begin sagging toward our latitude, which
could serve as a focus/track for storms from tonight into Wednesday.
This thermal and moisture gradient may be reinforced by outflow
boundaries from earlier storms. Will maintain 20-40% storm chances
overnight near and north of Osceola/Brevard counties, increasing to
40-60% north of I-4 before daybreak. The environment will be largely
the same, so a few of these storms could also be strong to severe.
Lows will be quite warm, in the low/mid 70s.

Wednesday...A frontal boundary will exist across north FL early
Wednesday and will slowly shift southward toward northern portions
of east central FL. Convective development may already be ongoing
just south of this boundary early in the morning across north FL or
into areas near to north of the Orlando metro area, where some
strong to isolated severe storms will already be possible. Rain
chances continue to rise then through the day with higher coverage
of showers and storms currently forecast across the area Wednesday,
with PoPs rising to 60-70 percent in a band of deeper moisture (PW
up to 1.8-2.0 inches) sliding southward across the area ahead of the
front. Strong westerly flow will exist between 925-700mb, up to 30-
40 knots, and temps at 500mb cool to around -10 to -11C, which will
continue the potential for strong to locally damaging winds and coin-
sized hail with any stronger storms storms that form. A brief
tornado or two can`t be completely ruled either. SPC maintains a
Marginal Risk (level 1 of 5) for severe weather across much of
central FL.

W/SW winds will be breezy with gusts up to 25 to 30 mph, especially
where some breaks in cloud cover can occur. Cloudier conditions
across northern central Florida will keep highs in the mid to upper
80s, but across Okeechobee County and the Treasure Coast hot and
muggy conditions expected to continue, with max temps reaching the
low to mid 90s and peak heat index values closer to 100-106.

Thursday-Friday...Frontal boundary shifts southward into central FL
with drier air building in north of this boundary. Currently have
greatest shower/storm chances, around 30-50 percent near to south of
a line from Lake Kissimmee to Melbourne, with PoPs 20 percent or
less to the north. However, these rain chances may shift farther
south, especially if the latest GFS solution holds, where PW values
of an inch or less make it all the way south to Indian River and
Osceola counties by the afternoon. Temps warm aloft to -8 to -9C and
offshore flow begins to weaken, so isolated severe threat should
diminish, but a strong storm or two may still be possible into the
afternoon on Thursday across southern portions of east central FL.
Front shifts back north of the area as a warm front by late week,
and while moisture increases some, rain chances have trended
lower to only around 20 percent for Friday as ridging begins to
build in aloft.

With the decreasing rain chances into late week, temperatures will
once again be on the rise across the entire area. It will be hotter
than normal, with highs in the low to mid 90s and heat index values
rising back to 98-103 on Friday. With drier air in place, lows on
Thursday night may be able to fall back into the mid to upper 60s
across much of the area, but milder overnight lows expected Friday
night, ranging from the low to mid 70s.

Saturday-Monday...Deeper moisture continues to build back into the
area during the weekend, as ridging aloft shifts east and mid/upper
level S/W trough moves into the Southeast U.S. pushing another front
toward the area on Sunday. This will increase rain chances to 30-50
percent on Saturday and 50 percent across all of east central FL on
Sunday. Scattered showers and storms will develop, mainly during the
afternoon and evening, with a few stronger storms again possible.
Hot conditions continue through the period, with highs into the 90s
and humid conditions producing peak heat index values around 100-105
each afternoon. GFS shows a cleaner frontal passage by Monday,
leading to a drier start to early next week, while ECMWF is wetter.
Will hold onto chance PoPs for Monday (30-50%), but there remains
some uncertainty with the model differences this far out.

&&

.AVIATION...
(06Z TAFs)
Issued at 400 AM EDT Tue May 14 2024

A weak warm front lifting through the area this morning is providing
some occasional MVFR CIGs through sunrise. Winds turn toward the SSW
early today, gusting 15-25 KT by late morning. A complex of storms
to our northwest has a 40-60% chance of affecting Daytona & Greater
Orlando terminals from roughly 15Z-19Z. A few of the storms could
contain gusts exceeding 35 KT. TEMPOs will likely be needed once the
timing becomes a little more clear. A sea breeze will turn winds to
the SE for most coastal terminals (perhaps DAB the exception) from
mid/late afternoon through sunset. A few storms could also develop
on the sea breeze early this evening at the coast, but confidence is
even lower at that time. Additional rounds of showers and storms
could affect the TAF sites after 15/09Z, especially Greater Orlando
& Daytona.

&&

.MARINE...
Issued at 400 AM EDT Tue May 14 2024

Today-Tonight... Had to extend the Small Craft Advisory to the coast
north of Sebastian Inlet through 8 AM as a wind surge affected the
waters. These winds will lessen this morning to SSE 15 KT nearshore,
and 15-20 KT offshore. Late this afternoon through tonight, winds
are forecast to freshen again out over the Gulf Stream to S 20-25
KT, where the Small Craft Advisory will continue into the night.
Winds/seas could be greater in the vicinity of storms that could
potentially move offshore around midday north of Cape Canaveral, and
again along the Space/Treasure Coasts this evening. There is also a
very low risk of a waterspout with today`s storms. Seas 3-4 FT,
increasing to 4-5 FT well offshore after midnight. Choppy for
inshore boaters today.

Wednesday-Saturday...Poor boating conditions continue offshore for
much of Wednesday into Wednesday night as W/SW winds remain up to 15-
20 knots. However, boating conditions then trend more favorable into
late week as winds diminish and seas decrease. Seas will range from
3-5 feet on Wednesday, to 2-4 feet Thursday and 1-2 feet on Friday.
S/SW winds on Saturday increase up to 10-15 knots, becoming S/SE
into the afternoon. Seas will continue increase slightly to 2-3
feet.

Scattered to numerous offshore moving storms will be possible on
Wednesday, with some strong to isolated severe storms possible. Rain
chances then decrease into late week, with only isolated offshore
moving storms possible, mainly south of Sebastian Inlet on Thursday,
then only a slight chance for offshore moving storms along the
entire east coast on Friday.

&&

.FIRE WEATHER...
Issued at 400 AM EDT Tue May 14 2024

Today-Tonight... Gusty south-southwest winds (10-15, G20-25 mph) are
forecast today for much of the district, potentially turning to the
SE along the coast late in the afternoon. Despite relatively muggy
conditions, unusually hot temperatures will allow RH readings to
fall to 40-45% over the Kissimmee Basin this afternoon. RH readings
will be higher elsewhere. Isolated to scattered storms are forecast,
with coverage highest north of Orlando-Titusville late this
morning/early afternoon. A few additional storms could develop along
the coast early this evening. Gusty/erratic winds will accompany the
stronger storms that form today.

Wednesday-Friday...Higher coverage of showers and storms, some
strong to severe will occur across the area Wednesday. Higher
moisture fueling these storms ahead of an approaching front will
keep min RH values above critical values, but will also produce
breezy W/SW winds. Front shifts southward into the area with drier
air building into the region Thursday. This will lead to min RH
values falling into the mid 30s to low 40s over much of the interior
Thursday afternoon. This will lead to more fire sensitive conditions
on this day, especially with westerly flow close to 15 mph.

Some moisture recovery expected into Friday, but Min RH values will
still fall to the low to mid 40s over the interior. SW winds will be
lighter around 5-10 mph, with sea breeze forming and pushing inland
switching winds to the E/SE to around 10 mph.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  90  72  87  70 /  60  50  70  10
MCO  94  74  89  73 /  50  40  70  30
MLB  92  74  90  73 /  50  50  70  40
VRB  94  74  95  72 /  50  50  70  40
LEE  90  75  86  72 /  60  60  70  20
SFB  92  75  88  72 /  50  50  70  20
ORL  93  75  89  73 /  50  40  70  20
FPR  94  73  95  71 /  50  50  70  40

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 8 AM EDT this morning for AMZ550-552.

     Small Craft Advisory until 4 AM EDT Wednesday for AMZ570-572-575.

&&

$$

SHORT TERM...Heil
LONG TERM...Weitlich
AVIATION...Heil