Alert archive / Georgia / Mesoscale Discussions in 2021
Mesoscale Discussion 1030
The Storm Prediction Center issued this mesoscale discussion at Jun 20, 2021, 8:40 AM EDT for 7 counties in Florida; 42 counties in Georgia; 7 counties in South Carolina. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 20, 2021, 8:40 AM EDT (12:40 UTC)
- Expired
- Jun 20, 2021, 11:15 AM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 56 counties
Baker County, FL, Columbia County, FL, Duval County, FL, Hamilton County, FL, Madison County, FL, Nassau County, FL, Suwannee County, FL, Appling County, GA, Atkinson County, GA, Bacon County, GA, Ben Hill County, GA, Berrien County, GA, Brantley County, GA, Brooks County, GA, Bryan County, GA, Bulloch County, GA, Burke County, GA, Camden County, GA, Candler County, GA, Charlton County, GA, Chatham County, GA, Clinch County, GA, Coffee County, GA, Cook County, GA, Echols County, GA, Effingham County, GA, Emanuel County, GA, Evans County, GA, Glynn County, GA, Irwin County, GA, Jeff Davis County, GA, Jenkins County, GA, Johnson County, GA, Lanier County, GA, Liberty County, GA, Long County, GA, Lowndes County, GA, McIntosh County, GA, Montgomery County, GA, Pierce County, GA, Screven County, GA, Tattnall County, GA, Telfair County, GA, Tift County, GA, Toombs County, GA, Treutlen County, GA, Ware County, GA, Wayne County, GA, Wheeler County, GA, Allendale County, SC, Bamberg County, SC, Barnwell County, SC, Beaufort County, SC, Colleton County, SC, Hampton County, SC, Jasper County, SC
The radar
The Jacksonville radar (KJAX), 130 km from the middle of the area, began a volume at 12:39 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
Jacksonville, FL (KJAX), launched 12:00Z, 0.7 hours before the alert went out and 129 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.
- Mixed-layer CAPE
- 1078 J/kg
- Mixed-layer CIN
- -61 J/kg
- Mixed-layer LCL
- 938 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 170 m²/s²
- 0-3 km storm-relative helicity
- 197 m²/s²
- Significant tornado parameter
- 0.7
- Supercell composite
- 9.6
The text
As transmitted.
386
ACUS11 KWNS 201241
SWOMCD
SPC MCD 201240
SCZ000-GAZ000-FLZ000-201515-
Mesoscale Discussion 1030
NWS Storm Prediction Center Norman OK
0740 AM CDT Sun Jun 20 2021
Areas affected...Eastern Georgia...Northeast Florida...Southern
South Carolina
Concerning...Severe potential...Watch possible
Valid 201240Z - 201515Z
Probability of Watch Issuance...60 percent
SUMMARY...A tornado threat may develop across parts of northeast
Florida, eastern Georgia and southern South Carolina this morning. A
tornado watch may need to be considered across this area.
DISCUSSION...Surface analysis shows that the remnant low of
Claudette is currently located in northwestern Georgia. A distinct
band of thunderstorms is ongoing to the southeast of the low, across
southwest and central Georgia. This band will continue to move
eastward this morning across eastern Georgia and southern South
Carolina. Intensification of the cells within the band of storms
will be possible as destabilization occurs. In addition, the WSR-88D
VWP near Charleston, South Carolina has 0-1 km shear near 35 kt with
0-3 km storm relative helicity in the 200 to 250 m2/s2 range. This
may support a tornado threat with rotating cells embedded in this
band of storms.
..Broyles/Edwards.. 06/20/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CHS...CAE...JAX...FFC...TAE...
LAT...LON 32098051 31488109 30838134 30408142 30138199 30148282
30308349 30638380 31408362 32168309 32958251 33358160
33188056 32928025 32428024 32098051SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 19, 8:00 PM EDT | Tornado Watch | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 9 more | 13 hr |
| Jun 20, 12:58 AM EDT | Mesoscale Discussion | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 9 more | 2 hr |
| Jun 20, 6:00 AM EDT | Mesoscale Discussion | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Hamilton and 9 more | 2 hr |
| Jun 20, 11:01 AM EDT | Mesoscale Discussion | SPC | Alachua, Bradford, Clay | 119 min |
| Jun 20, 2:43 PM EDT | Mesoscale Discussion | SPC | Calhoun, Chesterfield, Darlington, Dillon, Kershaw, Lee and 4 more | 92 min |
Nearby
Mesoscale Discussions in Georgia, 2021Mesoscale Discussions in Florida, 2021Mesoscale Discussions in South Carolina, 2021Every 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.