Alert archive / Florida / Tornado Watches in 2021

Tornado Watch 568

December 21, 202110 counties in Florida

The Storm Prediction Center issued this tornado watch at Dec 21, 2021, 5:22 AM EST for 10 counties in Florida. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Dec 21, 2021, 5:22 AM EST (10:22 UTC)
Expired: Dec 21, 2021, 10:00 AM EST
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

Counties Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Highlands County, FL, Lee County, FL, Manatee County, FL, Sarasota County, FL

The radar

The Tampa radar (KTBW), 129 km from the middle of the area, began a volume at 10:24 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 30%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 20%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 10%
One or more hailstones of 2 inches or more: 10%
Six or more combined severe hail and wind reports: 40%

Warnings issued inside it

1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Dec 21, 8:15 AM EST	Severe Thunderstorm Warning	TBW	Hillsborough, Manatee, Sarasota	30 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 00:00Z, 10.4 hours before the alert went out and 129 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 721 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 127 m²/s²
0-3 km storm-relative helicity: 194 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

657 
WWUS20 KWNS 211018
SEL8  
SPC WW 211018
FLZ000-CWZ000-211500-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 568
NWS Storm Prediction Center Norman OK
520 AM EST Tue Dec 21 2021

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Southwest Florida
  Coastal Waters

* Effective this Tuesday morning from 520 AM until 1000 AM EST.

* Primary threats include...
  A couple tornadoes possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...A long-lived supercell west of Naples may be maintained as
it reaches and spreads inland of the coast. An additional supercell
might develop farther north as well as low-level flow intensifies
this morning.

The tornado watch area is approximately along and 50 statute miles
either side of a line from 20 miles southwest of Fort Myers FL to 55
miles east northeast of Fort Myers FL. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU8).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

&&

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 24025.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 21, 4:33 AM EST	Mesoscale Discussion	SPC	Charlotte, Collier, DeSoto, Glades, Hardee, Hendry and 3 more	2 hr
Dec 21, 8:01 AM EST	Mesoscale Discussion	SPC	Charlotte, Collier, DeSoto, Hardee, Hendry, Lee and 2 more	89 min
Dec 21, 9:34 AM EST	Mesoscale Discussion	SPC	Charlotte, Collier, DeSoto, Glades, Hardee, Hendry and 4 more	26 min

Nearby

Tornado Watches in Florida, 2021 Every tornado watch 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.