Special Marine Warning 31, NWS Key West, FL

900 
FZUS72 KKEY 200541
MWSKEY

Marine Weather Statement
National Weather Service Key West FL
141 AM EDT Tue Apr 20 2021

GMZ035-200551-
/O.CAN.KKEY.MA.W.0031.000000T0000Z-210420T0600Z/
141 AM EDT Tue Apr 20 2021

...THE SPECIAL MARINE WARNING IS CANCELLED...

The affected areas were...
Gulf of Mexico from west end of Seven Mile Bridge to Halfmoon Shoal
out to 5 fathoms...

The thunderstorm has moved out of the warned area and no longer 
poses a significant threat to boaters.

LAT...LON 2472 8110 2477 8127 2495 8119 2508 8110
      2513 8105 2512 8100 2514 8096 2514 8090
      2517 8090 2518 8085 2520 8084 2521 8086
      2522 8083 2491 8093
TIME...MOT...LOC 0541Z 221DEG 13KT 2488 8101 

$$

GMZ031-032-200600-
/O.CON.KKEY.MA.W.0031.000000T0000Z-210420T0600Z/
141 AM EDT Tue Apr 20 2021

...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL 200 AM EDT...

For the following areas...
Bayside and Gulf side from Craig Key to west end of Seven Mile
Bridge...
Florida Bay including Barnes Sound, Blackwater Sound, and Buttonwood
Sound...

At 141 AM EDT, a strong thunderstorm was located near Sprigger Bank
Light, moving northeast at 15 knots.

HAZARD...Wind gusts 34 knots or greater.

SOURCE...National Weather Service Meteorologist.

IMPACT...Expect wind gusts in excess of 34 knots, suddenly higher 
         waves, frequent lightning, and heavy downpours.

Locations in the warning include...
Oxfoot Bank Light, Snake Bight, First National Bank, Bradley Key,
John Sawyer Bank Light, Man Of War Key and Frank Key.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for wind gusts in excess of 35 knots, steep and fast-building
seas, frequent lightning strikes, and blinding downpours. Stay low or
go below, and make sure all on board are wearing life jackets.

Intense and continuous lightning is occurring with this storm. If
caught on the open water, stay low or go below.

&&

LAT...LON 2472 8110 2477 8127 2495 8119 2508 8110
      2513 8105 2512 8100 2514 8096 2514 8090
      2517 8090 2518 8085 2520 8084 2521 8086
      2522 8083 2491 8093
TIME...MOT...LOC 0541Z 221DEG 13KT 2488 8101 

HAIL...0.00IN
WIND...>34KTS

$$

Jacobson

975 
FZUS72 KKEY 200557
MWSKEY

Marine Weather Statement
National Weather Service Key West FL
157 AM EDT Tue Apr 20 2021

GMZ031-032-200607-
/O.EXP.KKEY.MA.W.0031.000000T0000Z-210420T0600Z/
157 AM EDT Tue Apr 20 2021

...THE SPECIAL MARINE WARNING WILL EXPIRE AT 200 AM EDT...

The affected areas were... 
Bayside and Gulf side from Craig Key to west end of Seven Mile
Bridge...
Florida Bay including Barnes Sound, Blackwater Sound, and Buttonwood
Sound...

The thunderstorm has weakened and no longer is expected to produce 
wind gusts of 34 knots or higher.

LAT...LON 2472 8110 2477 8127 2495 8119 2508 8110
      2513 8105 2512 8100 2514 8096 2514 8090
      2517 8090 2518 8085 2520 8084 2521 8086
      2522 8083 2491 8093
TIME...MOT...LOC 0557Z 194DEG 13KT 2490 8101 

$$

Jacobson

Area Forecast Discussion
National Weather Service Key West FL
859 PM EDT Mon Apr 19 2021

.DISCUSSION...
A fairly active convective evening over the Florida Keys coastal
waters. Several thunderstorms have developed from cumulus fields
over the Florida Straits and progressed towards the northeast near
20 knots. Storm tops have been just shy of 45 kft, and have been
more organized than a typical pulse thunderstorm scenario. One
thunderstorm north of Key West breifly popped above 50 kft.This
is not surprising since the Key West evening sounding revealed a
good degree of convective instability. Precipitable water values
are up around 2 inches, and the boundary layer from 700mb down is
close to saturation. ML CAPE is approaching 3000 J/kg with
virtually no inhibition. Therefore, any lift from boundaries or
thunderstorm outflow will produce a convective cell. New cells are
now forming well southwest of the Lower Keys - also moving
swiftly towards the northwest. So it would seem that this
convection will last well into the overnight hours.

&&

.MARINE...
Scattered showers and thunderstorms will impact the Keys coastal
and nearshore waters for the remainder of the evening and
overnight. Some of these storms could be strong, producing wind
gusts approaching 34 knots. Storms that do develop will be moving
rapidly towards the northwest, between 20 and 25 knots. Winds will
be generally from the southwest around 10 knots, but can
dramatically shift and strengthen in the vicinity of showers and
storms.

&&

.AVIATION...
Although VFR conditions will generally prevail at both the Key
West and Marathon terminals, passing strong showers and storms can
result in brief periods of MVFR or even IFR conditions, mainly at
the Key West terminal overnight. There is not enough certainty in
the timing and location of the storms as the evening progresses,
so there may be amendments to the terminal forecast as events
unfold.

&&

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

Public/Marine/Fire...Devanas
Aviation/Nowcasts....Devanas
Data Acquisition.....KR

Visit us on the web at weather.gov/key

Follow us on Facebook and Twitter at:
www.facebook.com/nwskeywest
www.twitter.com/nwskeywest

Hazardous Weather Outlook
National Weather Service Key West FL
447 AM EDT Mon Apr 19 2021

FLZ076>078-GMZ031>035-042>044-052>055-072>075-200900-
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-
447 AM EDT Mon Apr 19 2021

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

.DAY ONE...TODAY AND TONIGHT

Isolated thunderstorms are possible late this afternoon and
tonight. The primary thunderstorm hazards will be cloud to surface
lightning strikes and locally strong gusty winds.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Isolated thunderstorms are possible on Thursday. The primary
thunderstorm hazard will be cloud to surface lightning strikes.

Otherwise, no hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

APA