Alert archive / Florida / Mesoscale Discussions in 2021

Mesoscale Discussion 73

February 13, 20218 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Feb 13, 2021, 5:38 AM EST for 8 counties in Florida. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Feb 13, 2021, 5:38 AM EST (10:38 UTC)
Expired: Feb 13, 2021, 8:15 AM EST
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Citrus County, FL, Hernando County, FL, Hillsborough County, FL, Lake County, FL, Marion County, FL, Pasco County, FL, Pinellas County, FL, Sumter County, FL

The radar

The Tampa radar (KTBW), 82 km from the middle of the area, began a volume at 10:40 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

Tampa Bay, FL (KTBW), launched 00:00Z, 10.6 hours before the alert went out and 83 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: 623 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 1097 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 30 m²/s²
0-3 km storm-relative helicity: -4 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

593 
ACUS11 KWNS 131038
SWOMCD
SPC MCD 131038 
FLZ000-131315-

Mesoscale Discussion 0073
NWS Storm Prediction Center Norman OK
0438 AM CST Sat Feb 13 2021

Areas affected...Tampa Bay and the FL west coast beaches...central
FL Peninsula

Concerning...Severe potential...Watch unlikely 

Valid 131038Z - 131315Z

Probability of Watch Issuance...5 percent

SUMMARY...A risk for isolated damaging gusts and/or a brief/weak
tornado will increase this morning as a squall line over the shelf
waters of the eastern Gulf of Mexico moves ashore between 7-8am EST.

DISCUSSION...Water-vapor imagery shows a wave-train of disturbances
moving from northern Mexico eastward into the Gulf of Mexico.  A
lead mid-level impulse is gradually moving east from the central
Gulf towards the FL Peninsula early today.  Radar mosaic shows a
squall line over the shelf waters west of Tampa Bay.  Linear
extrapolation places the squall line moving ashore the beaches
around 7am EST.  

At the surface, a stationary frontal zone is analyzed from
immediately north of the Tampa metro east-northeast towards Daytona
Beach.  Surface conditions south of the boundary are characterized
by temperatures near 70 deg F and dewpoints in the upper 60s and mid
60s north of the boundary.  Forecast soundings show veering
low-level flow increasing to 45 kt in the midlevels.  Although lapse
rates are modest, 250-500 J/kg MLCAPE is objectively analyzed and
expected prior to squall line passage.  However, adequate hodograph
curvature in the lowest 1-2 km and the presence of the boundary
perhaps suggest sufficient low-level vorticity potential for
mesovortexgenesis.  Isolated damaging gusts and possibly a tornado
could occur.  The overall risk appears to be limited in magnitude
and expected coverage to probably not warrant a severe thunderstorm
watch issuance.  However, convective trends will be monitored as the
squall line approaches the peninsula.

..Smith/Edwards.. 02/13/2021

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

ATTN...WFO...MLB...TBW...JAX...

LAT...LON   28798298 29328211 28938151 28068161 27398275 27848322
            28798298

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 13, 9:58 AM EST	Mesoscale Discussion	SPC	Brevard, Orange, Osceola, Polk, Seminole, Volusia	92 min

Nearby

Mesoscale Discussions in Florida, 2021 Every mesoscale discussion 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.