Alert archive / Florida / Mesoscale Discussions in 2021

Mesoscale Discussion 366

April 11, 202115 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Apr 11, 2021, 10:54 AM EDT for 15 counties in Florida. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 11, 2021, 10:54 AM EDT (14:54 UTC)
Expired: Apr 11, 2021, 1:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 91

Counties Brevard County, FL, Citrus County, FL, Hernando County, FL, Hillsborough County, FL, Lake County, FL, Manatee County, FL, Marion County, FL, Orange County, FL, Osceola County, FL, Pasco County, FL, Pinellas County, FL, Polk County, FL, Seminole County, FL, Sumter County, FL, Volusia County, FL

The radar

The Tampa radar (KTBW), 72 km from the middle of the area, began a volume at 14:55 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 12:00Z, 2.9 hours before the alert went out and 72 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: 1004 J/kg
Mixed-layer CIN: -131 J/kg
Mixed-layer LCL: 1005 m above ground
0-6 km bulk shear: 57 kt
0-1 km storm-relative helicity: 288 m²/s²
0-3 km storm-relative helicity: 296 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.3

Open this sounding in Storm Lab

The text

As transmitted.

702 
ACUS11 KWNS 111454
SWOMCD
SPC MCD 111454 
FLZ000-111700-

Mesoscale Discussion 0366
NWS Storm Prediction Center Norman OK
0954 AM CDT Sun Apr 11 2021

Areas affected...central portions of the Florida Peninsula

Concerning...Severe Thunderstorm Watch 91...

Valid 111454Z - 111700Z

The severe weather threat for Severe Thunderstorm Watch 91
continues.

SUMMARY...Storms continue to develop across/spread into central
Florida/WW 91.  Risk for damaging winds is expected to ramp up over
the next couple of hours, beginning over western portions of the
watch.

DISCUSSION...Latest surface analysis shows an outflow boundary lying
west-to-east across central Florida, from roughly Tampa to Orlando
to Melbourne.  A loosely organized warm-advection band of storms is
occurring north of this boundary, from roughly Citrus to
Seminole/Orange Counties, where local wind/hail potential exists.

Meanwhile, a much larger area of storms remains over the eastern
Gulf of Mexico, with the leading edge of this convection now
approaching coastal Citrus/Hernando/Pasco/Pinellas Counties.  This
band has remained rather loosely defined, but has recently begun to
take ona bit more of an organized/bowing character.  This more
organized/advancing portion of the band will move onshore across the
aforementioned counties over the next hour, and should progress
eastward in the vicinity of the outflow boundary.  The organizing
character of the storms, and focused ascent in the vicinity of the
boundary, suggests a corridor of enhanced severe risk evolving in
the short term.

..Goss.. 04/11/2021

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

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

LAT...LON   28508365 28928319 29258260 29488096 28948059 28148054
            27798158 27178256 27348335 27838348 28508365

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 11, 5:27 AM EDT	Mesoscale Discussion	SPC	Alachua, Bradford, Citrus, Clay, Dixie, Flagler and 14 more	3 hr
Apr 11, 8:15 AM EDT	Severe Thunderstorm Watch	SPC	Alachua, Brevard, Citrus, DeSoto, Dixie, Flagler and 23 more	8 hr
Apr 11, 12:08 PM EDT	Mesoscale Discussion	SPC	Brevard, Hillsborough, Manatee, Orange, Osceola, Polk and 1 more	2 hr
Apr 11, 1:24 PM EDT	Mesoscale Discussion	SPC	Broward, Charlotte, Collier, DeSoto, Glades, Hardee and 11 more	2 hr
Apr 11, 2:03 PM EDT	Severe Thunderstorm Watch	SPC	Broward, Charlotte, Collier, Glades, Hendry, Lee and 3 more	6 hr
Apr 11, 4:12 PM EDT	Mesoscale Discussion	SPC	Broward, Collier, Hendry, Lee	2 hr

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.