Alert archive / Florida / Mesoscale Discussions in 2020

Mesoscale Discussion 421

April 20, 202010 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2020, 2:00 PM EDT for 10 counties in Florida. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2020, 2:00 PM EDT (18:00 UTC)
Expired: Apr 20, 2020, 3:30 PM EDT
In force: 90 min
Issued by: the Storm Prediction Center

Counties DeSoto County, FL, Hardee County, FL, Highlands County, FL, Indian River County, FL, Manatee County, FL, Okeechobee County, FL, Osceola County, FL, Polk County, FL, Saint Lucie County, FL, Sarasota County, FL

The radar

The Tampa radar (KTBW), 83 km from the middle of the area, began a volume at 18:00 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, 6.0 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: 1093 J/kg
Mixed-layer CIN: -37 J/kg
Mixed-layer LCL: 989 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 351 m²/s²
0-3 km storm-relative helicity: 431 m²/s²
Significant tornado parameter: 2.4
Supercell composite: 22.1

Open this sounding in Storm Lab

The text

As transmitted.

596 
ACUS11 KWNS 201801
SWOMCD
SPC MCD 201800 
FLZ000-201930-

Mesoscale Discussion 0421
NWS Storm Prediction Center Norman OK
0100 PM CDT Mon Apr 20 2020

Areas affected...Portions of the central/southern FL Peninsula

Concerning...Severe Thunderstorm Watch 127...

Valid 201800Z - 201930Z

The severe weather threat for Severe Thunderstorm Watch 127
continues.

SUMMARY...An isolated strong to locally damaging wind threat
continues. The severe risk should gradually diminish this afternoon.
An additional downstream watch is not expected.

DISCUSSION...Supercells that developed earlier along the FL Space
Coast have moved offshore, with a trailing broken line of storms
continuing to move east-southeastward around 30-40 kt across the
central FL Peninsula. Although the airmass downstream of this
ongoing convection remains quite unstable (MLCAPE 2000-2500 J/kg)
and deep-layer is strong, the large-scale forcing over this region
is becoming increasingly marginal. Low-level winds have also veered
to southwesterly, limiting hodograph curvature. Therefore, the
primary threat for the next hour or so remains isolated strong to
damaging wind gusts, with a lower threat for a tornado than earlier.
Current expectations are for low/mid-level winds to gradually
diminish through the rest of the afternoon, with a gradual reduction
in storm organization and intensity. A downstream watch into south
FL is not currently anticipated.

..Gleason.. 04/20/2020

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

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

LAT...LON   27418259 28188171 28288056 27468023 27178096 26918238
            27418259

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 19, 10:39 PM EDT	Tornado Watch	SPC	Escambia, Okaloosa, Santa Rosa	5 hr
Apr 19, 10:53 PM EDT	Mesoscale Discussion	SPC	Gadsden, Holmes, Jackson, Walton, Washington	67 min
Apr 19, 11:13 PM EDT	Tornado Watch	SPC	Bay, Calhoun, Dixie, Franklin, Gadsden, Gulf and 11 more	10 hr
Apr 20, 1:52 AM EDT	Mesoscale Discussion	SPC	Alachua, Baker, Bradford, Clay, Columbia, Duval and 6 more	83 min
Apr 20, 2:19 AM EDT	Tornado Watch	SPC	Alachua, Baker, Bradford, Clay, Columbia, Duval and 9 more	9 hr
Apr 20, 6:19 AM EDT	Mesoscale Discussion	SPC	Alachua, Baker, Bradford, Citrus, Clay, Columbia and 16 more	86 min
Apr 20, 7:02 AM EDT	Severe Thunderstorm Watch	SPC	Brevard, Citrus, Hardee, Hernando, Hillsborough, Lake and 11 more	8 hr
Apr 20, 8:18 AM EDT	Mesoscale Discussion	SPC	Alachua, Citrus, Flagler, Levy, Marion, Putnam and 2 more	87 min
Apr 20, 11:06 AM EDT	Mesoscale Discussion	SPC	Brevard, Hardee, Hernando, Hillsborough, Indian River, Lake and 10 more	114 min

Nearby

Mesoscale Discussions in Florida, 2020 Every mesoscale discussion in 2020

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.