Alert archive / Florida / Mesoscale Discussions in 2021

Mesoscale Discussion 368

April 11, 202117 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Apr 11, 2021, 1:24 PM EDT for 17 counties in Florida. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 11, 2021, 1:24 PM EDT (17:24 UTC)
Expired: Apr 11, 2021, 3:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 91

Counties Broward County, FL, Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Highlands County, FL, Indian River County, FL, Lee County, FL, Martin County, FL, Miami-Dade County, FL, Monroe County, FL, Okeechobee County, FL, Palm Beach County, FL, Saint Lucie County, FL, Sarasota County, FL

The radar

The Tampa radar (KTBW), 146 km from the middle of the area, began a volume at 17:28 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 92Apr 11, 2:00 PM EDT

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 12:00Z, 5.4 hours before the alert went out and 146 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.

510 
ACUS11 KWNS 111724
SWOMCD
SPC MCD 111724 
FLZ000-111930-

Mesoscale Discussion 0368
NWS Storm Prediction Center Norman OK
1224 PM CDT Sun Apr 11 2021

Areas affected...parts of central and southern Florida

Concerning...Severe Thunderstorm Watch 91...

Valid 111724Z - 111930Z

The severe weather threat for Severe Thunderstorm Watch 91
continues.

SUMMARY...Severe risk continues locally across parts of central
Florida -- within WW 91 -- and will gradually shift southward
requiring new WW consideration across much of south Florida.

DISCUSSION...Latest radar loop shows a band of storms sagging
southward across central Florida, with occasionally stronger
storms/convective segments noted.  As outflow associated with this
band shifts steadily southward, the primary zone of severe risk will
likewise shift south -- and eventually out of the current WW.

Meanwhile, as the very moist south Florida airmass continues to
warm/destabilize, additional/cellular development is occurring south
of the main convective band.  Given sufficient shear across the
area, a few of these storms could produce gusty winds and hail,
prior to the arrival of storms from the north.  Given these trends,
a new WW will likely be required in the next 60 to 90 minutes,
across much of south Florida.

..Goss.. 04/11/2021

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

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

LAT...LON   27138297 27428251 27688149 27878018 26977977 25937990
            25568042 25538144 26138241 27138297

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, 10:54 AM EDT	Mesoscale Discussion	SPC	Brevard, Citrus, Hernando, Hillsborough, Lake, Manatee and 9 more	2 hr
Apr 11, 12:08 PM EDT	Mesoscale Discussion	SPC	Brevard, Hillsborough, Manatee, Orange, Osceola, Polk and 1 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.