Alert archive / Florida / Special Marine Warnings in 2021

Special Marine Warning 13, NWS Key West, FL

April 12, 2021

NWS Key West, FL issued this special marine warning at Apr 12, 2021, 1:19 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, 1:19 AM EDT (05:19 UTC)
Expired: Apr 12, 2021, 2:15 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), 62 km from the middle of the area, began a volume at 05:21 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, 5.3 hours before the alert went out and 66 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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.

205 
WHUS52 KKEY 120519
SMWKEY
GMZ033-120615-
/O.NEW.KKEY.MA.W.0013.210412T0519Z-210412T0615Z/

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

The National Weather Service in Key West has issued a

* Special Marine Warning for...
  Gulf Waters from East Cape Sable to Chokoloskee 20 to 60 nm out and
  beyond 5 fathoms...

* Until 215 AM EDT.

* At 118 AM EDT, a strong to perhaps severe cluster of thunderstorms 
  with possible waterspouts was located near P Tower, moving 
  southeast at 20 to 25 knots.

  HAZARD...Waterspouts and wind gusts 40 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.

* Locations in the warning include...
  P Tower.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for severe thunderstorms with wind gusts in excess of 50
knots, extremely rough seas, frequent lightning, and torrential
downpours. Be advised that any severe thunderstorm can spawn a
waterspout or tornado. Stay low or go below, and make sure all on
board are wearing life jackets.

&&

LAT...LON 2512 8221 2537 8202 2517 8153 2483 8161
TIME...MOT...LOC 0518Z 295DEG 31KT 2518 8204 

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

$$

APA

1 follow-up statement

357 
FZUS72 KKEY 120547
MWSKEY

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

GMZ033-120615-
/O.CON.KKEY.MA.W.0013.000000T0000Z-210412T0615Z/
147 AM EDT Mon Apr 12 2021

...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL 215 AM EDT...

For the following areas...
Gulf Waters from East Cape Sable to Chokoloskee 20 to 60 nm out and
beyond 5 fathoms...

At 145 AM EDT, a cluster of strong to severe thunderstorms with 
possible waterspouts was located 13 nm east of P Tower, moving east 
southeast near 35 knots.

HAZARD...Waterspouts and wind gusts 45 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. In 
         addition, small hail is possible. 

Locations in the warning include...
P Tower.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for severe thunderstorms with wind gusts in excess of 50
knots, extremely rough seas, frequent lightning, and torrential
downpours. Be advised that any severe thunderstorm can spawn a
waterspout or tornado. 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 2508 8204 2529 8195 2517 8153 2483 8161
TIME...MOT...LOC 0545Z 290DEG 49KT 2509 8176 

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

$$

APA

The office that day

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

Issued	Product	Office	Lasted
Apr 11, 8:12 PM EDT	Special Marine Warning	KEY	63 min
Apr 12, 2:11 AM EDT	Special Marine Warning	KEY	50 min
Apr 12, 5:31 AM EDT	Special Marine Warning	KEY	59 min
Apr 12, 6:25 AM EDT	Special Marine Warning	KEY	65 min
Apr 12, 6:32 AM EDT	Special Marine Warning	KEY	58 min
Apr 12, 7:04 AM EDT	Special Marine Warning	KEY	26 min
Apr 12, 7:19 AM EDT	Special Marine Warning	KEY	18 min
Apr 12, 7:28 AM EDT	Special Marine Warning	KEY	62 min
Apr 12, 7:34 AM EDT	Special Marine Warning	KEY	56 min
Apr 12, 7:43 AM EDT	Special Marine Warning	KEY	47 min
Apr 12, 8:32 AM EDT	Special Marine Warning	KEY	43 min
Apr 12, 8:40 AM EDT	Special Marine Warning	KEY	35 min
Apr 12, 9:16 AM EDT	Special Marine Warning	KEY	29 min
Apr 12, 9:45 AM EDT	Special Marine Warning	KEY	30 min
Apr 12, 10:44 AM EDT	Small Craft Advisory	KEY	6 hr

Nearby

Special Marine Warnings in Florida, 2021 Every 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.