Alert archive / Florida / Special Marine Warnings in 2021

Special Marine Warning 21, NWS Key West, FL

April 12, 2021

NWS Key West, FL issued this special marine warning at Apr 12, 2021, 7:34 AM EDT. It was in force for 56 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Apr 12, 2021, 7:34 AM EDT (11:34 UTC)
Expired
Apr 12, 2021, 8:30 AM EDT
In force
56 min
Issued by
NWS Key West, FL
Area
Storm-based polygon
Hail
0.0 in
Wind
34.0 mph

The radar

The Key West radar (KBYX), 96 km from the middle of the area, began a volume at 11:35 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Key West, FL (KEYW), launched 00:00Z, 11.6 hours before the alert went out and 92 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Key West, FL at 00:00Z on 2021-04-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3145 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Key West, FL at 00:00Z on 2021-04-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 117 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
3145 J/kg
Mixed-layer CIN
-9 J/kg
Mixed-layer LCL
760 m above ground
0-6 km bulk shear
44 kt
0-1 km storm-relative helicity
117 m²/s²
0-3 km storm-relative helicity
127 m²/s²
Significant tornado parameter
2.7
Supercell composite
11.6

Open this sounding in Storm Lab

The text

As transmitted.

688 
WHUS52 KKEY 121134
SMWKEY
GMZ074-075-121230-
/O.NEW.KKEY.MA.W.0021.210412T1134Z-210412T1230Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Special Marine Warning
National Weather Service Key West FL
734 AM EDT Mon Apr 12 2021

The National Weather Service in Key West has issued a

* Special Marine Warning for...
  Straits of Florida from west end of Seven Mile Bridge to 20 nm west
  of Dry Tortugas 20 to 60 nm out...

* Until 830 AM EDT.

* At 734 AM EDT, a strong thunderstorm with possible waterspouts was
  located 31 nm southwest of Wood's Wall West Crack, moving southeast
  at 10 knots.

  HAZARD...Waterspouts and wind gusts 34 knots or greater.

  SOURCE...National Weather Service Meteorologist.

  IMPACT...Waterspouts can quickly form and capsize boats, cause 
           considerable damage to vessels and create suddenly higher 
           waves. Expect wind gusts in excess of 34 knots, suddenly 
           higher waves, frequent lightning, and heavy downpours.

* The strong thunderstorm will remain over mainly open waters.

LAT...LON 2391 8247 2401 8226 2394 8185 2366 8216
TIME...MOT...LOC 1134Z 309DEG 8KT 2390 8227 

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

$$

BT
1 follow-up statement
946 
FZUS72 KKEY 121159
MWSKEY

Marine Weather Statement
National Weather Service Key West FL
759 AM EDT Mon Apr 12 2021

GMZ075-121209-
/O.CAN.KKEY.MA.W.0021.000000T0000Z-210412T1230Z/
759 AM EDT Mon Apr 12 2021

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

LAT...LON 2387 8242 2398 8221 2394 8185 2366 8216
TIME...MOT...LOC 1159Z 309DEG 8KT 2386 8222 

$$

GMZ074-121230-
/O.CON.KKEY.MA.W.0021.000000T0000Z-210412T1230Z/
759 AM EDT Mon Apr 12 2021

...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL 830 AM EDT...

For the following areas...
Straits of Florida from west end of Seven Mile Bridge to south of
Halfmoon Shoal 20 to 60 nm out...

At 759 AM EDT, a strong thunderstorm with possible waterspouts was
located 31 nm southwest of Wood's Wall West Crack, moving southeast
at 10 knots.

HAZARD...Waterspouts and wind gusts 34 knots or greater.

SOURCE...National Weather Service Meteorologist.

IMPACT...Waterspouts can quickly form and capsize boats, cause 
         considerable damage to vessels and create suddenly higher 
         waves. Expect wind gusts in excess of 34 knots, suddenly 
         higher waves, frequent lightning, and heavy downpours.

The strong thunderstorm will remain over mainly open waters.

LAT...LON 2387 8242 2398 8221 2394 8185 2366 8216
TIME...MOT...LOC 1159Z 309DEG 8KT 2386 8222 

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

$$

BT

The office that day

Everything else NWS Key West, FL issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 11, 8:12 PM EDTSpecial Marine WarningKEY63 min
Apr 12, 1:19 AM EDTSpecial Marine WarningKEY56 min
Apr 12, 2:11 AM EDTSpecial Marine WarningKEY50 min
Apr 12, 5:31 AM EDTSpecial Marine WarningKEY59 min
Apr 12, 6:25 AM EDTSpecial Marine WarningKEY65 min
Apr 12, 6:32 AM EDTSpecial Marine WarningKEY58 min
Apr 12, 7:04 AM EDTSpecial Marine WarningKEY26 min
Apr 12, 7:19 AM EDTSpecial Marine WarningKEY18 min
Apr 12, 7:28 AM EDTSpecial Marine WarningKEY62 min
Apr 12, 7:43 AM EDTSpecial Marine WarningKEY47 min
Apr 12, 8:32 AM EDTSpecial Marine WarningKEY43 min
Apr 12, 8:40 AM EDTSpecial Marine WarningKEY35 min
Apr 12, 9:16 AM EDTSpecial Marine WarningKEY29 min
Apr 12, 9:45 AM EDTSpecial Marine WarningKEY30 min
Apr 12, 10:44 AM EDTSmall Craft AdvisoryKEY6 hr

Nearby

Special Marine Warnings in Florida, 2021Every special marine warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.