008
FXUS62 KMLB 260233
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
1033 PM EDT Wed Sep 25 2024

...New UPDATE...

.UPDATE...
Issued at 1030 PM EDT Wed Sep 25 2024

Local preparations ahead of Hurricane Helene`s impacts should now
be complete. Conditions are forecast to deteriorate overnight into
Thursday morning as the cyclone intensifies, moving north-
northeastward over the eastern Gulf of Mexico. Most locations have
experienced a brief break from the rain in the last hour or two,
but another outer rain band from Helene is impacting the Treasure
Coast and is expected to continue north toward the Space Coast in
the next 1-2 hours. These heavy showers will pack gusty winds of
30 to 45 mph as they quickly move from south to north. Continued
episodes of gusty rain bands, intermixed with periods of dry time,
will last through sunrise Thursday.

Deeper moisture is advecting northward and will continue to do so
tonight, as the surface pressure gradient tightens over the
Florida Peninsula. The evening XMR sounding showed quite the
increase in moisture when compared to this morning`s data (1.86"
PW at 15z to 2.25" at 00z). RAP analysis indicates MLCAPE around
1000 J/kg along the coast, and model guidance suggests this will
expand overnight as MLCIN begins to decrease. Surface- based CIN
will also erode gradually through the night, with SBCAPE climbing
to 1000-2000 J/kg along and east of Interstate 95. Hi- res
guidance depicts the highest lightning chances focused near the
coast or just offshore. Gusty winds to 45 mph and a brief
waterspout or tornado cannot be ruled out through sunrise along
the coast. Be sure to have multiple ways to receive warnings, in
the event they are issued later tonight. Conditions will
worsen on Thursday with daytime heating and increasing low/mid
level wind shear enhancing the already gusty squalls expected
across the state. The tornado threat is forecast to increase
during the daylight hours, along with the potential for locally
heavy rainfall. Continue to monitor weather.gov, NOAA Weather
Radio, and local news outlets for updated, official information on
Helene.

&&

.PREVIOUS DISCUSSION...
Issued at 224 PM EDT Wed Sep 25 2024

-Hurricane Helene will lift north over the eastern Gulf of Mexico
 through Thursday and produce heavy rain, strong winds, and
 possible tornadoes. Rough, battering surf will produce dangerous
 conditions at the beaches.

-Preparations for Helene should be underway and completed by this
 afternoon, with conditions deteriorating tonight.

-Hot and humid late week behind "Helene" as plume of deep moisture
 returns and keeps a threat for heavy rain this weekend.

Rest of Today-Tonight...Any preparations ahead of Hurricane Helene
should be rushed to completion this afternoon. Conditions will
deteriorate tonight. Until then, showers and storms embedded
within the moisture plume of Helene continue across the area this
afternoon. Gusty winds have been reported along the coast, with
the St Lucie Nuclear Power Plant reporting a 47mph wind gust
earlier today along the barrier island from a storm. Expect
showers and storms to increase from south to north, with outer
rainbands reaching southern portions of east central Florida this
evening. Tropical Storm Warnings remain in effect.

Training showers and storms, along with ample tropical moisture
(2.25-2.5" PWATs) could produce locally heavy rainfall in some
locations. Given the recent heavy rainfall over several areas
earlier this month, have issued a Flood Watch for the entire
forecast area. Be sure to have multiple ways to receive warnings
overnight tonight. Increasing SRH, particularly along and north of
the I-4 corridor, will quickly increase the tornado threat into
the early morning hours. Breezy southeasterly flow will keep
overnight lows in the mid to upper 70s.

A High Surf Advisory has been issued through Friday morning, with
seas building into Thursday. If heading to the beach, be cautious of
large, surging waves in the surf zone. Do not enter the water.

Thursday-Thursday Night...Conditions will further deteriorate
through the morning hours on Thursday, as Helene makes its closest
approach to the area while forecast to be a Major hurricane.
Gusty squalls will increase in frequency into the afternoon, as
southeasterly to southerly winds increase to 20-40mph, with gusts
50-55mph. A few gusts to 60mph cannot be ruled out in the afternoon,
with 925mb winds around 50kts.The strongest winds will be along
and north of the I-4 corridor, which will be closest to the storm
itself. Models suggests periods of dry air being wrapped around
the storm at its closest approach. However, with 1-4" forecast and
locally higher amounts possible in training bands, will continue
the Flood Watch due to recent heavy rains this month. The tornado
threat looks to peak Thursday afternoon into the evening hours,
with forecast STP values around 1+ and low level SRH increases.

Temperatures look to be moderated by precipitation, cloud cover,
and a well mixed atmosphere. However, should the sun break through
in any dry slots, temperatures could reach values higher than
currently forecast. For now, have high temperatures reaching the
mid to upper 80s, as deep moisture surges heat indices to near
100. Dangerous beach conditions will persist through the impact
phase of Hurricane Helene. If heading to the beach, be cautious of
large, surging waves in the surf zone. Do not enter the water.
Conditions will begin to improve Thursday night. However, gusty
winds will persist through the overnight hours.

Fri-Tue (modified previous)...Models show a dry slot moving into
the area from the SW on the backside of Helene as it lifts
northward into GA then the TN Valley Thu night/early Fri. But, a
plume of deep moisture will remain across south FL and return
northward over central FL late Fri into the weekend. Hot, breezy
SW flow on Fri- Sat will produce max temps in the lower 90s even
at the coast. Combined with high humidity, peak heat indices will
climb to 104-108. Storm coverage looks higher on Sat, when the
deep moisture is squarely over the area, so have drawn 60 PoP
areawide. Then decreasing rain chances Sun (40-50 percent) and
Mon/Tue (30-40 percent).

&&

.MARINE...
Issued at 224 PM EDT Wed Sep 25 2024

Tropical Storm Warnings are in effect for the adjacent Atlantic
waters out to 60 nm. Hurricane Helene is forecast to continue to
strengthen over eastern Gulf of Mexico and accelerate into the FL
Big Bend late Thursday. Boating conditions will continue to
deteriorate tonight, as southeast winds increase to 25-30kts by
daybreak, then 30-40kts Thursday afternoon. Seas building 7-8ft
tonight, then peaking at 13ft offshore Volusia and Brevard
Thursday afternoon into Thursday night. Deep moisture lifting
northward will support a high coverage of showers and storms
through Thursday. Winds will become southwest Friday, decreasing
to 20-25kts and will continue to gradually decrease to near 15
knots late Friday night. Seas quickly subsiding below 5 ft along
the coast due to the offshore component but remaining 6-7 ft
offshore Friday. Flow remains offshore (W to SW) Saturday-Sunday
up to 15 knots, with seas subsiding 3-4 Saturday and 2-3 ft Sun.
There will be scattered to numerous storms pushing offshore
especially Saturday.

&&

.AVIATION...
(00Z TAFs)
Issued at 725 PM EDT Wed Sep 25 2024

Scattered to isolated showers and storms will continue across east
central Florida over the next several hours. Conditions are then
forecast to deteriorate across the terminals late tonight into
Thursday as outer rainbands from Hurricane Helene move across east
central Florida, with prevailing SHRA and VCTS forecast. Tried to
capture timing of a potential dry slot between 10-18Z across the
interior terminals and between 13-18Z across the coastal terminals
tomorrow, with the CAM guidance in decent agreement on this
timing. Additional rainbands are then forecast to set up after
18Z, with continual SHRA and VCTS through the remainder of the
period beyond 00Z. Sustained winds of 20 to 30 knots with gusts
beyond 30 knots are forecast out of the south to southeast
tomorrow. Also added in mention of LLWS after 18Z, with
FL015 reaching 45kt out of the south.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  77  88  78  92 /  60  90  60  40
MCO  77  88  79  90 /  50  90  60  50
MLB  79  88  79  92 /  60  80  70  60
VRB  78  89  79  92 /  60  80  70  70
LEE  77  87  78  90 /  60  90  60  30
SFB  77  88  79  91 /  50  90  60  50
ORL  78  88  80  91 /  50  90  60  50
FPR  78  88  78  92 /  60  70  70  70

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Tropical Storm Warning for FLZ041-044>046-053-058-141-144-154-
     159-164-247-254-259-264-347-447-547-647-747.

     Flood Watch through Friday morning for FLZ041-044>046-053-058-
     141-144-154-159-164-247-254-259-264-347-447-547-647-747.

     High Surf Advisory until 11 AM EDT Friday for FLZ141-154-159-164-
     347-447-647-747.

AM...Tropical Storm Warning for AMZ550-552-555-570-572-575.

&&

$$

UPDATE...Schaper
AVIATION...Tollefsen