Special Marine Warning 129, NWS Key West, FL

Area Forecast Discussion
National Weather Service Key West FL
415 AM EDT Mon Aug 9 2021

.DISCUSSION...
Scattered showers and isolated storms have developed during the
last couple of hours over the southeastern Gulf of Mexico, but
radar detects very little shower activity along the Keys and
eastward across the Straits to Andros Island. This is consistent
with an easterly wind surge which has moved across the area during
the night, with the activity over the Gulf waters forming in an
area of low level speed convergence along the leading edge of this
surge. Skies are mostly clear along the island chain, with
temperatures hovering in the lower to mid 80s, and winds on land
from the east to southeast at 10 to 15 mph. Surface and upper air
analysis depict a dominant subtropical ridge over the central and
western Atlantic, with the western end of the ridge over Florida
and the Gulf of Mexico beginning to strengthen as a mid latitude
trough along the Mid Atlantic coast moves northeast. The 00Z Key
West sounding was quite moist, with PW of 2.13 inches, but a
considerably drier airmass is entering our area from the east,
with estimated PWs around 1.5 inches moving west of Andros Island
into the eastern Straits.

Our weather regime through the next few days will be dominated by
the strengthening subtropical ridge, with moderate easterly flow
prevailing across the Keys. There will be significant dry air in
the mid levels, with PWs generally running below normal for this
time of year, as the large area of relative dryness evident in
MIMIC imagery from the western Bahamas back through Puerto Rico
and eastward into the tropical Atlantic translates westward
across the Keys. This will keep PoPs in check despite the stronger
than normal easterly flow for August, with the best rain chances
occurring during the late night and early morning hours.

Heading to the end of the work week and into the weekend,
attention will turn to a tropical wave currently in the Atlantic
Ocean a few hundred miles east of the Leeward Islands. This
feature has a 60 percent chance of becoming a tropical cyclone
during the next 5 days as per NHC, although it should be noted
that the bulk of the model guidance suite moves the system near
the high terrain of the Greater Antilles, with not much
development indicated. For now, the forecast will continue with
the idea of a strong tropical wave approaching our area Thursday
night and Friday, then moving through Friday night into Saturday,
with rain chances climbing above normal. The latest runs of both
the GFS and ECMWF show weak low pressure moving northward near or
just west of the Florida peninsula during the later part of the
weekend, as the wave and associated moisture turn poleward into a
weakness in the subtropical ridge. This would result in the Keys
staying in a very moist airmass for a longer period of time, with
rain chances probably ending up higher than currently shown for
the later part of the weekend.

&&

.MARINE...
Overnight observations show increasing E/SE breezes across the
Keys coastal waters, with C-MAN and Weatherflow sites along the
reef and at Smith Shoal Light running in the 10 to 14 knot range
during the past few hours. Moderate easterly breezes will prevail
across the waters today through Thursday. A tropical disturbance
will move west northwest through the Greater Antilles during the
week, and is forecast to move across the Keys and South Florida
Friday through Saturday.

&&

.AVIATION...
VFR and gentle easterly breezes will prevail at the EYW and MTH
terminals through the morning. Satellite derived moisture products
from GOES and MIMIC indicate a drier airmass moving into the Florida
Keys. Rain chances will be slight for both terminals, and slim
enough to not include a VC for much of the TAF.

&&

.CLIMATE...
On this date in 1950, from the Key West Citizen, "thousands of fish
were found in the streets of Key West after a heavy rain. Most of
the fish were found along Caroline Street between William and
Grinnell. One theory was that a large waterspout had carried the
fish ashore. This theory was supported by the fact that most of
the fish were mullet, which swim on the surface and could be
picked up by a waterspout. Caroline Street regulars insisted it
had rained fish, and one man said he saw a full-grown sponge fall
from the sky."

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

Public/Marine/Fire..........Jacobson
Aviation/Climate/Nowcasts...CLR

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Hazardous Weather Outlook
National Weather Service Key West FL
417 AM EDT Mon Aug 9 2021

FLZ076>078-GMZ031>035-042>044-052>055-072>075-101000-
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-
417 AM EDT Mon Aug 9 2021

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

.DAY ONE...TODAY AND TONIGHT

Isolated thunderstorms will be possible today and tonight. The
primary thunderstorm hazards will be lightning strikes and locally
gusty winds.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Isolated thunderstorms will be possible Tuesday through Thursday
night, with scattered storms becoming more likely Friday through
Saturday as a tropical wave moves across the area. The primary
thunderstorm hazards will be lightning strikes and locally gusty
winds.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.