EF0 tornado, Big Coppit Is, Florida, November 15, 2023

Area Forecast Discussion
National Weather Service Key West FL
405 AM EST Wed Nov 15 2023

...New DISCUSSION, MARINE, AVIATION...

.DISCUSSION...
Issued at 430 AM EST Wed Nov 15 2023

A very dynamic weather pattern is unfolding across the area due to
an upper shortwave trough over the Gulf of Mexico and associated
cyclogenesis. This low formation, along with a robust surface high
blanketing the eastern United States and Atlantic, are generating
strong easterly breezes. There is quite a wind speed disparity
with significantly stronger breezes over our eastern zones. In
addition, this changing of the synoptic guard is resulting in
considerable moistening and convective support both aloft and in
the lower levels. Recent radar data indicates shower activity has
proliferated across the area over the past few hours. However,
electrical activity has been absent.

Through today and into tonight the upper level trough will drive
eastward through Florida and essentially orphan the gulf low it
assisted in birthing. That said, the combination of the gulf low
and the high to our north will maintain a broad swath of strong
east to southeasterly breezes across Florida and clipping into the
Keys area. The increasing kinematics down low and dynamics aloft
will continue to moisten and destabilize the environment. This
will almost certainly result in rounds of showers and potentially
thunderstorms today and tonight. Given the expected cloud cover
and rain potential, expect day time highs to top out near normal
and dew points holding in the lower 70s.

Uncertainty in the short term is unusually high. Guidance has, for
some time now, indicated that new cyclogenesis will begin tonight
just Atlantic side of South Florida as upper level support shifts
eastward. The specifics on where, shape, and strength of the
expected pressure falls will have enormous influences on wind and
rain chances for tonight and tomorrow. Should the low form further
southwest over the Keys, portions of the island chain could face
excessive rainfall and near gale force sustained winds. If said
development is further north, the Keys could be largely missed
with winds flagging in a nebulous pressure field and squalls
passing us by to the north. For now, will maintain very high pops
for today and tonight and winds generally trending downwards.

Through the remainder of the weak, winds will be light and, at
times, variable due to the lack of a driving pressure gradient.
Drier air invading from the west and northwest aloft will also
keep rain chances at a minimum. Expect temperatures to range near
to slightly above normal with dew points remaining near 70.

A true airmass changeover is possible beginning this weekend as a
high cell descending down the Plains assists in driving drier and
and perhaps slightly cooler northerlies into the Keys. However,
uncertainty again reigns supreme as some solutions are hinting at
a more progressive pattern. Stay tuned.

&&

.MARINE...
Issued at 430 AM EST Wed Nov 15 2023

The combination of a robust east coast surface high and a
deepening gulf low will result in a swath of strong easterly
breezes across Florida and portions of Keys waters today into
tonight. Uncertainty is considerable in the short term as a new
low is expected to take shape off South Florida's east coast
tonight and will have a major influence on our resulting wind
vectors. A Small Craft Advisory remains in effect for all Keys
waters.

&&

.AVIATION...
(06Z TAFS)
Issued at 430 AM EST Wed Nov 15 2023

Shallow fast moving showers and gusty east winds will continue to
impact both terminals today. Thundery squalls will become more
likely later this morning as noted by introduction of VCTS.
Prevailing MVFR CIGS and TEMPO IFR VIS will be possible late
Wednesday morning into Wednesday afternoon. Although not included
outside of ongoing TEMPO groups at this time, convective wind gusts
could approach 30 to 35 knots. Exact ending time of precipitation
remains uncertain and possibly out of the current TAF period with
current best guess early Thursday morning.

&&

.CLIMATE...
On this day in Keys weather history in 1916, a tropical storm that
developed in the central Caribbean Sea acquired extratropical
characteristics over the SE Gulf of Mexico and moved rapidly
northeast along the entire length of the Keys. Sand Key recorded
maximum sustained winds of 71 mph, while Key West reported maximum
sustained winds of 52 mph with a minimum pressure reading of
29.70" or 1006 mb.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.

&&

Public/Marine/Fire...11
Aviation/Nowcasts....JAM
Data Acquisition.....JAM

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Hazardous Weather Outlook
National Weather Service Key West FL
456 AM EST Wed Nov 15 2023

FLZ076>078-GMZ031>035-042>044-052>055-072>075-161000-
Monroe Upper Keys-Monroe Middle Keys-Monroe Lower Keys-
Florida Bay including Barnes Sound, Blackwater Sound, and
Buttonwood Sound-
Bayside and Gulf side from Craig Key to west end of Seven Mile
Bridge-
Gulf waters from East Cape Sable to Chokoloskee 20 to 60 NM out
and beyond 5 fathoms-
Gulf of Mexico including Dry Tortugas and Rebecca Shoal Channel-
Gulf of Mexico from west end of Seven Mile Bridge to Halfmoon
Shoal out to 5 Fathoms-
Hawk Channel from Ocean Reef to Craig Key out to the reef-
Hawk Channel from Craig Key to west end of Seven Mile Bridge out
to the reef-
Hawk Channel from west end of Seven Mile Bridge to Halfmoon Shoal
out to the reef-
Straits of Florida from Ocean Reef to Craig Key out 20 NM-
Straits of Florida from Craig Key to west end of Seven Mile
Bridge out 20 NM-
Straits of Florida from west end of Seven Mile Bridge to south of
Halfmoon Shoal out 20 NM-
Straits of Florida from Halfmoon Shoal to 20 NM west of Dry
Tortugas out 20 NM-
Straits of Florida from Ocean Reef to Craig Key 20 to 60 NM out-
Straits of Florida from Craig Key to west end of Seven Mile
Bridge 20 to 60 NM out-
Straits of Florida from west end of Seven Mile Bridge to south of
Halfmoon Shoal 20 to 60 NM out-
Straits of Florida from Halfmoon Shoal to 20 NM west of Dry
Tortugas 20 to 60 NM out-
456 AM EST Wed Nov 15 2023

This Hazardous Weather Outlook is for the Florida Keys and
adjacent coastal waters.

.DAY ONE...Today and tonight.

Strong easterly breezes will relax tonight. A Small Craft
Advisory is in effect for all of the Florida Keys coastal waters
for winds increasing to near 20 knots.

A combination of elevated tides and potentially heavy rainfall
tonight will result in ponding on roadways and low-lying areas. A
Coastal Flood Statement is in effect for the Florida Keys island
chain.

Isolated to scattered thunderstorms will be possible. The primary
threats for any thunderstorm will be locally gusty winds and
cloud to surface lightning strikes.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Small Craft Advisory conditions will be possible for portions of
the Florida Keys coastal waters on Thursday. Although winds are
should slacken tonight, seas are expected to remain elevated in
the eastern coastal waters through Thursday evening.

Predicted tides are expected to remain high over the next several
days. A Coastal Flood Statement or Advisory will likely remain in
effect for portions or all of the Florida Keys through late in
the week or the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Preliminary Local Storm Report
National Weather Service Key West FL
536 AM EST Wed Nov 15 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0256 AM     Tstm Wnd Gst     8 ESE North Key Largo   25.23N 80.21W
11/15/2023  E39 MPH          GMZ042             FL   Mesonet

            The Weatherflow Mesonet at Carysfort Reef
            Light measured a east southeast wind gust of
            34 knots, or 39 mph, at 2:56 AM with a
            passing squall.

&&

JAM