Mesoscale Discussion 1535

Issued

Aug 16, 2021, 3:55 PM EDT (19:55 UTC)

Expired

Aug 16, 2021, 6:00 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Tornado watch 441

Counties Dixie County, FL, Gilchrist County, FL, Jefferson County, FL, Lafayette County, FL, Levy County, FL, Taylor County, FL

The Tallahassee radar (KTLH), 114 km from the middle of the area, began a volume at 19:58 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.

888 
ACUS11 KWNS 161955
SWOMCD
SPC MCD 161955 
FLZ000-162200-

Mesoscale Discussion 1535
NWS Storm Prediction Center Norman OK
0255 PM CDT Mon Aug 16 2021

Areas affected...Northern and Eastern Apalachee Bay Coast

Concerning...Tornado Watch 441...

Valid 161955Z - 162200Z

The severe weather threat for Tornado Watch 441 continues.

SUMMARY...The highest tornado potential for the next 1-2 hours may
reside over northern and eastern coastal areas of Apalachee Bay as
weak thunderstorms move onshore in the coming hours.

DISCUSSION...Tropical Storm Fred continues to move northward and has
made landfall on the FL Panhandle per the latest updates from the
NHC. To the north of the center of circulation, velocity data and
VWP observations from KTLH, as well as recent RAP mesoanalysis,
suggest low-level shear is maximized west of Tallahassee, FL owing
to a maxima in Fred's wind field. However, persistent stratiform
rain has reduced near-surface theta-e values as temperatures
struggle to warm above the mid 70s, resulting in a minimum in
MLCAPE. Subsequently, storms away from Fred's center moving into
this region have shown weakening trends. Given the strongly sheared
environment, a brief tornado remains possible, but the probability
for a robust tornado threat seems reduced. 

Further to the east, low-level trajectories from north/central FL
are advecting higher theta-e air into Fred's eastern rain bands.
This higher-quality air mass is denoted by MLCAPE values exceeding
1000 J/kg in recent analyses, and should continue to support storm
development over the next few hours. Deepening convection is noted
within a developing band that will likely move towards the northern
and eastern Apalachee Bay coast over the coming hours. Although
low-level shear diminishes with eastern extent, there should be a
sufficient overlap of favorable low-level SRH and instability to
maintain a tornado threat for at least the next 1-2 hours for the
north/eastern coastal areas of the bay.

..Moore.. 08/16/2021

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

ATTN...WFO...TBW...JAX...TAE...

LAT...LON   30068427 30478406 30518373 30328325 30108291 29808263
            29438258 29138259 28998273 29028311 29218325 29468345
            29718364 29908393 29968412 30068427

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.