Mesoscale Discussion 2050

Issued

Dec 21, 2021, 4:33 AM EST (09:33 UTC)

Expired

Dec 21, 2021, 7:00 AM EST

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

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, Sarasota County, FL

The Miami radar (KAMX), 154 km from the middle of the area, began a volume at 09:34 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.

• Tornado Watch 568Dec 21, 5:20 AM EST

311 
ACUS11 KWNS 210934
SWOMCD
SPC MCD 210933 
FLZ000-211200-

Mesoscale Discussion 2050
NWS Storm Prediction Center Norman OK
0333 AM CST Tue Dec 21 2021

Areas affected...South FL

Concerning...Severe potential...Watch possible 

Valid 210933Z - 211200Z

Probability of Watch Issuance...40 percent

SUMMARY...Several strong to severe thunderstorms may occur over
south FL this morning. Damaging wind gusts are the main threat, but
a brief tornado is also possible. A watch may be needed to cover
this severe potential.

DISCUSSION...Recent KTBW radar imagery shows several stronger storms
about 50 to 60 nm off the southwest FL coast. The most intense
thunderstorm is about 50 nm west-southwest of APF. Current motion of
this storm is northeastward at around 25 kt, bringing it to the
coast very close to 11Z. Thermodynamic conditions along the coast
are modest, with temperatures in the upper 60s/low 70s, dewpoints in
the upper 60s, and MLCAPE between 250 and 500 J/kg. Based on recent
mesoanalysis and RAP forecast soundings, modest convective
inhibition is in place, owing to a relatively warm thermodynamic
profile. 

The overall kinematic profile is a bit more favorable for organized
thunderstorms, with weak easterly/northeasterly wind veering to
moderate west-southwesterly flow in the mid levels and strong
southwesterly flow in the upper levels. This profile results in 40
to 50 kt of effective bulk shear. Low-level flow is relatively weak,
but the strong veering still results in over 150 m2/s2 of 0-1 km
storm-relative helicity.

The modest thermodynamics will likely limit overall storm coverage
and severity early this morning, with some improvement possible
after diurnal heating begin. Additionally, large-scale forcing for
ascent will increase, as will low to mid-level flow. This should
result in increasing storm coverage and a few stronger, more
organized storms. In very near-term, the storm about 50 nm off APF
may be intense enough for updraft maintenance to persist inland.
Damaging wind gusts are the main threat with this storm (and any
other development), with some low probability potential for a brief
tornado as well. Some questions remain regarding overall storm
coverage, but enough storms could develop to merit watch issuance
and convective trends are being monitored closely.

..Mosier/Grams.. 12/21/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MFL...MLB...TBW...

LAT...LON   25738164 26178188 26878240 27318262 27578222 27528119
            26988083 26308075 25808093 25708125 25738164

Mesoscale Discussions in Florida, 2021Every mesoscale discussion in 2021

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.