Area Forecast Discussion
Issued by NWS Jacksonville, FL
FXUS62 KJAX 011833
Area Forecast Discussion
National Weather Service Jacksonville FL
233 PM EDT SAT OCT 1 2016
.SHORT TERM...Tonight and Sunday...Frontal boundary now situated
just beyond the coastal waters and extending sw across central
Florida. This boundary will gradually lift back to the nw on
Sunday along with moisture as large upper low over the Ohio
valley lifts north. For this afternoon and tonight a few showers
and thunderstorms may develop over se zones se of a SGJ-OCF line
where higher moisture resides. On Sunday the chances for rain
will spread nw into the Jacksonville and Gainesville areas. With a
tight moisture gradient over the area...low temperatures tonight
will have a large range. Lows will be in the upper 50s over interior
se Ga to around 70 at the coast.
.LONG TERM /Monday into Friday/... General comments...The
extended range forecast is highly dependent upon the extended
range motion of Hurricane Matthew, the ultimate size of its wind
envelope, the distance at its closest point of approach and,
probably most important locally, it`s interactions with a very
strong high pressure center north of the tropical system.
Beach and oceanfront interests should prepare for the possibility of
an extended duration high surf and beach erosion event beginning on
Tuesday and continuing into the weekend. interests in north Florida
and southeast Georgia...and especially beach and marine
interests...should closely monitor NHC/NWS messaging about the storm
and its the future progress.
Monday...ECMWF and GFS are in decent agreement at this point. There
is an upper level short wave trough across the central Gulf of
Mexico with the western periphery of the Bermuda Ridge extending
toward Cape Canaveral and the weakness north of Matthew is over
eastern Cuba and the Windward Passage. A surface ridge will be
building over the northern states with a mild wedge/local
northeaster building in down the southeast coast. Coastal winds are
modest at this point with an east to east-northeasterly flow at 10
to 15 mph and some convergent bands moving in from off the ocean.
Tuesday...On Tuesday...and days forward...the new GFS model run has
shifted between 60 to 90 miles further east of the previous solution
with the 00 utc ECMWF model significantly further seaward of GFS.
This will make a very big difference as to how strong the coastal
pressure gradient will be and the strength of the developing
northeaster along our coast. So on Tuesday Matthew should be passing
across the Bahamian Out Islands with a gradually tightening pressure
gradient along our coast. Seas will be beginning to build and surf
will be choppy and blown out with a 15 to 25 mph onshore flow. The
expected convergent bands not associated with the hurricane will
be moving onshore with some locally heavy rainfall, especially
late in the day.
Wednesday...The main player locally is going to be the interaction
between the 1030 mb ridge over the New England states and Matthew
emerging from the northern Bahamas...or even east of the Bahamas.
Matthew is going to have a very large wind envelope and the pressure
gradient along our coast should be able to support sustained winds
of 20 to 30 mph with gusts to gale force possible. Surf will be very
rough and choppy with strong rip currents likely. Again. it is
important to emphasize this isn`t the hurricane itself but the
interaction between it and the ridge!
Thursday and Friday...This is where things get very,very tricky
(see the first paragraph). The GFS exhibits the furthest west
solution with the ECMWF, HWRF and Consensus models significantly
further east. This will have implications for the strength of the
northeaster as the system makes its closest point of approach on
Thursday and Friday...assuming it doesn`t slow down further. At
this time, based on GFS, it looks like we could see gale force
conditions over the coastal waters and possibly impinging on the
immediate beaches. High battering surf and potential deadly rip
currents are possible. Conversely with the further east ECMWF (00
utc model run) solution we experience a more modest northeaster
with 20 to 25 mph winds with higher gusts. It is important to
realize we do not have the 12 utc ECMWF model run in at the time
this discussion was written.
Friday night and Saturday...If Matthew follows the script the system
should be pulling away to our north with drying conditions and
a north to northwesterly flow. Seas and surf will be very slow to
subside, especially if Matthew takes a more easterly track and
allows a swell to radiate back toward the coast.
.AVIATION...VFR conditions expected into Sunday. VCSH possible at
.MARINE...Northeast winds over the waters will become southerly
tonight as frontal boundary lifts back north. Onshore winds and
seas will increase by midweek as pressure gradient tightens
between high pressure to the north and Hurricane Matthew lifting
north through the Bahamas. Dangerous boating conditions will
likely develop especially offshore.
Rip Currents: Moderate risk for ne Fl beaches due to long period
swells. Low risk for se Ga through Sunday. Elevated risk expected
to continue through next week.
.PRELIMINARY POINT TEMPS/POPS...
AMG 59 89 65 88 / 0 10 0 20
SSI 69 85 69 84 / 10 20 20 40
JAX 68 88 70 87 / 10 30 20 40
SGJ 70 85 70 85 / 20 50 20 60
GNV 65 88 68 86 / 0 40 20 50
OCF 68 87 70 86 / 10 40 20 60