Alert archive / Florida / Special Weather Statements in 2018

Special Weather Statement, NWS Key West, FL

December 20, 2018

NWS Key West, FL issued this special weather statement at Dec 20, 2018, 3:38 PM EST. It was in force for 52 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
Dec 20, 2018, 3:38 PM EST (20:38 UTC)
Expired
Dec 20, 2018, 4:30 PM EST
In force
52 min
Issued by
NWS Key West, FL

The radar

The Key West radar (KBYX), 32 km from the middle of the area, began a volume at 20:42 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

Miami, FL (KMFL), launched 12:00Z, 8.6 hours before the alert went out and 168 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, Miami, FL at 12:00Z on 2018-12-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 343 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, Miami, FL at 12:00Z on 2018-12-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 262 square meters per square second.1939587897Sfc1 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
343 J/kg
Mixed-layer CIN
-14 J/kg
Mixed-layer LCL
787 m above ground
0-6 km bulk shear
55 kt
0-1 km storm-relative helicity
262 m²/s²
0-3 km storm-relative helicity
271 m²/s²
Significant tornado parameter
0.6
Supercell composite
4.1

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Key West, FL wrote its last area forecast discussion before this special weather statement went out at Dec 20, 11:40 AM EST, 3 hours 58 minutes earlier.

Area forecast discussion, Dec 20, 11:40 AM EST, 3 hours 58 minutes before
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Hazardous weather outlook, Dec 20, 5:19 AM EST, 10 hours 19 minutes before
Hazardous Weather Outlook
National Weather Service Key West FL
519 AM EST Thu Dec 20 2018

FLZ076>078-GMZ031>035-042>044-052>055-072>075-211030-
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-
519 AM EST Thu Dec 20 2018

...STRONG COLD FRONT WILL IMPACT THE KEYS TODAY THROUGH FRIDAY
NIGHT...

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

.DAY ONE...TODAY AND TONIGHT

A strong cold front is expected to blast through the Florida Keys
and adjacent coastal waters during the afternoon and evening
hours. This front is expected to bring multiple weather hazards
to the Keys for today through Friday evening, including strong to
severe thunderstorms, strong winds on land with gales likely on
the coastal waters, and possible coastal flooding on the Gulf and
Bayside.

The potential for strong to severe thunderstorms ahead of the
cold front will be highest across the Keys this afternoon and
tonight. These thunderstorms are expected to organize into a
squall line which is forecast to move through the Keys during the
late afternoon or evening hours. The primary hazards with any
thunderstorms will be strong, gusty and shifting winds along with
lightning strikes. Some of the thunderstorms, either embedded
within the squall line or developing out ahead of the line, could
become severe with damaging winds and large hail. Isolated
waterspouts will also be possible, and there is a slight risk for
tornadoes as well. The Storm Prediction Center continues to
include all of South Florida and the Keys within a severe
thunderstorm risk area for today into tonight.

On land, gusty south to southwest winds will increase to 20 to 30
mph today, then shift toward the west and increase to 25 to 30
mph tonight. This will probably require a Wind Advisory to be
issued later today or tonight.

These persistent and strong westerly winds will cause Coastal
Flooding impacts from the north side of the Lower Keys through the
Gulf side and Bayside communities of the Middle and Upper Keys
beginning late tonight. See the latest Coastal Flood Statement
for additional details.

A Gale Warning has been issued for all of the Keys coastal
waters, and SMALL CRAFT SHOULD REMAIN IN PORT today through
Friday. Weather will change rapidly today into tonight. South to
southwest winds will increase today with frequent gusts to near
gale force becoming likely, then full on westerly gales are
expected tonight. An intense squall line likely will move through
Keys coastal waters during the afternoon and evening, with a
slight risk for a few severe thunderstorms. Very large seas are
also expected during this event.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Strong sustained west winds around 30 mph with gusts near
40 mph are expected along the Keys island chain on Friday. This
will require a Wind Advisory to be issued.

The strong westerly winds will cause Coastal Flooding impacts to
continue from the north side of the Lower Keys through the Gulf
side and Bayside communities of the Middle and Upper Keys Friday
and Friday night. Total water levels may reach 3 to 4.5 feet
above mean sea level for the Bayside communities of the eastern
Middle Keys and the Upper Keys Friday and Friday night. The
maximum water levels likely will occur within Buttonwood Sound,
Tarpon Basin, and Blackwater Sound, around the times of high tide.
Water levels will begin to slowly subside on Saturday. See the
latest Coastal Flood Statement for additional details. A Coastal
Flood Warning may be required for the Middle and Upper Keys.

SMALL CRAFT SHOULD REMAIN IN PORT on Friday, when westerly gale
conditions are expected. Very large seas will peak on Friday at
11 to 19 feet across the Straits of Florida and deep waters of the
southeastern Gulf of Mexico, 5 to 8 feet across Hawk Channel
inside the reef, and 4 to 8 feet across the Gulf waters inside
five fathoms.

Winds should drop below Small Craft Advisory levels on the Keys
coastal waters Saturday morning, but lingering high seas will
remain above 7 feet over the Florida Straits and deep waters of
the southeastern Gulf of Mexico through Saturday afternoon or
evening.

.SPOTTER INFORMATION STATEMENT...

Weather spotters and emergency management officials are
encouraged to report severe thunderstorms, waterspouts, strong
winds, heavy rainfall, hail or coastal flooding to the National
Weather Service Forecast Office in Key West.

In the hours before

Special weather statement, Dec 20, 3:38 PM EST, 0 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Dec 20, 3:10 AM ESTSpecial Marine WarningKEY50 min
Dec 20, 4:14 AM ESTGale WarningKEY42 hr
Dec 20, 5:19 AM ESTCoastal Flood StatementKEYMonroe43 hr
Dec 20, 6:28 AM ESTSpecial Marine WarningKEY47 min
Dec 20, 11:58 AM ESTSpecial Marine WarningKEY2 hr
Dec 20, 12:45 PM ESTSpecial Marine WarningKEY60 min
Dec 20, 1:27 PM ESTSpecial Marine WarningKEY93 min
Dec 20, 2:56 PM ESTSpecial Marine WarningKEY94 min
Dec 20, 3:45 PM ESTCoastal Flood AdvisoryKEYMonroe43 hr
Dec 20, 4:16 PM ESTSpecial Marine WarningKEY89 min
Dec 20, 6:10 PM ESTSpecial Marine WarningKEY50 min
Dec 20, 6:55 PM ESTSpecial Weather StatementKEY50 min
Dec 20, 6:56 PM ESTSpecial Marine WarningKEY64 min

Nearby

Special Weather Statements in Florida, 2018Every special weather statement in 2018

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.