Alert archive / Georgia / Mesoscale Discussions in 2021
Mesoscale Discussion 117
The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2021, 7:09 AM CST for 10 counties in Florida; 27 counties in Georgia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 18, 2021, 7:09 AM CST (13:09 UTC)
- Expired
- Feb 18, 2021, 9:15 AM CST
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 37 counties
Bay County, FL, Calhoun County, FL, Franklin County, FL, Gadsden County, FL, Gulf County, FL, Jackson County, FL, Jefferson County, FL, Leon County, FL, Liberty County, FL, Wakulla County, FL, Atkinson County, GA, Baker County, GA, Ben Hill County, GA, Berrien County, GA, Brooks County, GA, Calhoun County, GA, Coffee County, GA, Colquitt County, GA, Cook County, GA, Crisp County, GA, Decatur County, GA, Dodge County, GA, Dooly County, GA, Dougherty County, GA, Grady County, GA, Irwin County, GA, Lanier County, GA, Lee County, GA, Miller County, GA, Mitchell County, GA, Seminole County, GA, Telfair County, GA, Thomas County, GA, Tift County, GA, Turner County, GA, Wilcox County, GA, Worth County, GA
The radar
The Tallahassee radar (KTLH), 41 km from the middle of the area, began a volume at 13:08 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.
The nearest sounding before it
Tallahassee Rgnl, FL (KTLH), launched 12:00Z, 1.2 hours before the alert went out and 41 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
- 104 J/kg
- Mixed-layer CIN
- -77 J/kg
- Mixed-layer LCL
- 497 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 387 m²/s²
- 0-3 km storm-relative helicity
- 410 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.3
The text
As transmitted.
700
ACUS11 KWNS 181309
SWOMCD
SPC MCD 181309
GAZ000-FLZ000-ALZ000-181515-
Mesoscale Discussion 0117
NWS Storm Prediction Center Norman OK
0709 AM CST Thu Feb 18 2021
Areas affected...southern GA...FL Panhandle
Concerning...Severe potential...Watch possible
Valid 181309Z - 181515Z
Probability of Watch Issuance...60 percent
SUMMARY...A conditional severe risk will continue through the
morning. The timing of another tornado watch is uncertain due in
part to the nebulous time period in which storm intensification will
occur, but a tornado watch will likely be needed at some point for
the FL Panhandle into southern GA as destabilization occurs.
DISCUSSION...Radar imagery shows several cells intermittently
exhibiting structures characteristic of marginal supercells located
to the west of Cape San Blas as of 13 UTC. Low-level moisture
advection has led to lower 60s F dewpoints infiltrating the eastern
part of the FL Panhandle and into the southern tier of counties in
GA. Further moistening is expected this morning as a warm frontal
zone gradually advances northward in southern GA. As heating occurs
today, weak surface-based buoyancy is forecast (250-750 J/kg SBCAPE)
across most of the discussion area towards the early afternoon.
Strong and increasing flow with height supports a profile for
supercells and line segments. Current projections are for a gradual
intensification of storms coincident with destabilization owing to
the diurnal cycle and low-level moisture advection. A tornado risk,
in addition to the threat for isolated damaging gusts, would
seemingly accompany the strongest storms. Convective trends will be
monitored.
..Smith/Edwards.. 02/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAX...FFC...TAE...
LAT...LON 30058592 31378480 32268381 32148285 31648262 31248282
30158406 29298493 29508578 30058592SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 17, 10:18 PM CST | Mesoscale Discussion | SPC | Bay, Calhoun, Escambia, Gulf, Okaloosa, Santa Rosa and 2 more | 2 hr |
| Feb 18, 1:49 AM CST | Tornado Watch | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 7 more | 6 hr |
| Feb 18, 4:54 AM CST | Mesoscale Discussion | SPC | Bay, Gulf | 2 hr |
| Feb 18, 7:45 AM CST | Tornado Watch | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Jackson and 6 more | 7 hr |
| Feb 18, 10:35 AM CST | Mesoscale Discussion | SPC | Gadsden, Jefferson, Leon, Liberty, Wakulla | 115 min |
| Feb 18, 12:43 PM CST | Mesoscale Discussion | SPC | Jefferson, Madison, Taylor | 92 min |
Nearby
Mesoscale Discussions in Georgia, 2021Mesoscale Discussions in Florida, 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.