Alert archive / Georgia / Mesoscale Discussions in 2021

Mesoscale Discussion 604

May 12, 202122 counties in Florida; 23 counties in Georgia

The Storm Prediction Center issued this mesoscale discussion at May 12, 2021, 12:30 PM EDT for 22 counties in Florida; 23 counties in Georgia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 12, 2021, 12:30 PM EDT (16:30 UTC)
Expired: May 12, 2021, 2:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 168

All 45 counties

Baker County, FL, Bay County, FL, Bradford County, FL, Calhoun County, FL, Clay County, FL, Columbia County, FL, Duval County, FL, Franklin County, FL, Gadsden County, FL, Gilchrist County, FL, Gulf County, FL, Hamilton County, FL, Jefferson County, FL, Lafayette County, FL, Leon County, FL, Liberty County, FL, Madison County, FL, Nassau County, FL, Suwannee County, FL, Taylor County, FL, Union County, FL, Wakulla County, FL, Atkinson County, GA, Bacon County, GA, Berrien County, GA, Brantley County, GA, Brooks County, GA, Camden County, GA, Charlton County, GA, Clinch County, GA, Coffee County, GA, Colquitt County, GA, Cook County, GA, Decatur County, GA, Echols County, GA, Glynn County, GA, Grady County, GA, Irwin County, GA, Lanier County, GA, Lowndes County, GA, Mitchell County, GA, Pierce County, GA, Thomas County, GA, Tift County, GA, Ware County, GA

The radar

The Tallahassee radar (KTLH), 64 km from the middle of the area, began a volume at 16:31 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

Tallahassee Rgnl, FL (KTLH), launched 12:00Z, 4.5 hours before the alert went out and 61 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: 263 J/kg
Mixed-layer CIN: -88 J/kg
Mixed-layer LCL: 1066 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 108 m²/s²
0-3 km storm-relative helicity: 139 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

Open this sounding in Storm Lab

The text

As transmitted.

207 
ACUS11 KWNS 121630
SWOMCD
SPC MCD 121630 
GAZ000-FLZ000-121830-

Mesoscale Discussion 0604
NWS Storm Prediction Center Norman OK
1130 AM CDT Wed May 12 2021

Areas affected...Southern Georgia and north Florida

Concerning...Severe Thunderstorm Watch 168...

Valid 121630Z - 121830Z

The severe weather threat for Severe Thunderstorm Watch 168
continues.

SUMMARY...An isolated severe threat remains possible across WW 168
through the early afternoon hours. Damaging winds will remain the
primary concern.

DISCUSSION...The line of storms that progressed through the AL/GA/FL
region continues to move into south-central GA, but has undergone
considerable weakening over the past 2 hours with warming cloud tops
and a drop-off in lightning noted. To the southwest across the FL
Panhandle, new convection continues to develop along an outflow
boundary, though these cells have exhibited transient behavior -
likely due to somewhat weak forcing for ascent. Ahead of this
activity across north FL and southern/southeast GA, temperatures
continue to warm into the low 80s with SBCAPE increasing as
inhibition gradually erodes. Increasing instability coupled with
adequate deep-layer shear over the region may support additional
storms and/or re-intensification of ongoing convection across north
FL and southeast GA that may support a damaging wind (and perhaps
marginally severe hail) threat through early afternoon. However,
considerable uncertainty remains due to weak low-level flow and
generally weak forcing for ascent. A downstream watch is still not
anticipated, but trends will continue to be monitored.

..Moore.. 05/12/2021

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

ATTN...WFO...CHS...JAX...TAE...

LAT...LON   30238589 31188438 31708357 31648246 31398139 30748105
            30158113 29778175 29628283 29728385 29748446 29488502
            29578542 29858587 30238589

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 12, 7:43 AM EDT	Mesoscale Discussion	SPC	Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 6 more	2 hr
May 12, 8:14 AM EDT	Severe Thunderstorm Watch	SPC	Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 9 more	6 hr
May 12, 10:17 AM EDT	Mesoscale Discussion	SPC	Bay, Calhoun, Franklin, Gadsden, Gulf, Hamilton and 7 more	118 min

Nearby

Mesoscale Discussions in Georgia, 2021 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.