Alert archive / Georgia / Mesoscale Discussions in 2021
Mesoscale Discussion 122
The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2021, 1:43 PM EST for Jefferson County, Madison County, Taylor County, Florida; 9 counties in Georgia. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Feb 18, 2021, 1:43 PM EST (18:43 UTC)
- Expired
- Feb 18, 2021, 3:15 PM EST
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 11
Counties Jefferson County, FL, Madison County, FL, Taylor County, FL, Atkinson County, GA, Berrien County, GA, Brooks County, GA, Colquitt County, GA, Cook County, GA, Echols County, GA, Lanier County, GA, Lowndes County, GA, Thomas County, GA
The radar
The Tallahassee radar (KTLH), 53 km from the middle of the area, began a volume at 18:41 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, 6.7 hours before the alert went out and 50 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.
409
ACUS11 KWNS 181843
SWOMCD
SPC MCD 181843
GAZ000-FLZ000-182015-
Mesoscale Discussion 0122
NWS Storm Prediction Center Norman OK
1243 PM CST Thu Feb 18 2021
Areas affected...the eastern Florida Panhandle through southern
Georgia
Concerning...Tornado Watch 11...
Valid 181843Z - 182015Z
The severe weather threat for Tornado Watch 11 continues.
SUMMARY...Threat for a couple of severe storms for the remaining
portion of WW 11 including the eastern Florida Panhandle through
southern GA will persist into the afternoon, but appears marginal.
DISCUSSION...Early this afternoon a band of mostly showers with a
few embedded thunderstorms persists from the central FL Panhandle
into southwest and south central GA and is associated with modest
ascent along a 40 kt southwesterly low level jet. Destabilization of
the boundary layer in this region has been slow and gradual due to
anvil plumes spreading downstream. Moreover, mid-level lapse rates
are very weak with an inversion evident between 700 and 500 mb.
Trends in VWP data from Tallahassee show winds have veered to
southwesterly in the lowest 2 km resulting in relatively small 0-1
km hodographs in warm sector, but deep shear of 40-45 kt remains
supportive of updraft rotation. Given the potential limiting factors
in the thermodynamic and low-level kinematic environment as well as
limited forcing for ascent through a deeper layer, overall threat
appears somewhat marginal this afternoon, but a couple of severe
storms cannot be ruled out.
..Dial.. 02/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAX...TAE...
LAT...LON 29488457 30218419 31238378 31458270 30638290 29618380
29488457SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 17, 11:18 PM EST | Mesoscale Discussion | SPC | Bay, Calhoun, Escambia, Gulf, Okaloosa, Santa Rosa and 2 more | 2 hr |
| Feb 18, 2:49 AM EST | Tornado Watch | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Holmes and 7 more | 6 hr |
| Feb 18, 5:54 AM EST | Mesoscale Discussion | SPC | Bay, Gulf | 2 hr |
| Feb 18, 8:09 AM EST | Mesoscale Discussion | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Jackson and 4 more | 2 hr |
| Feb 18, 8:45 AM EST | Tornado Watch | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Jackson and 6 more | 7 hr |
| Feb 18, 11:35 AM EST | Mesoscale Discussion | SPC | Gadsden, Jefferson, Leon, Liberty, Wakulla | 115 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.