Alert archive / Florida / Mesoscale Discussions in 2021
Mesoscale Discussion 1533
The Storm Prediction Center issued this mesoscale discussion at Aug 16, 2021, 12:36 PM EDT for Franklin County, Taylor County, Wakulla County, Florida. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Aug 16, 2021, 12:36 PM EDT (16:36 UTC)
- Expired
- Aug 16, 2021, 2:30 PM EDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 441
Counties Franklin County, FL, Taylor County, FL, Wakulla County, FL
The radar
The Tallahassee radar (KTLH), 70 km from the middle of the area, began a volume at 16:38 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, 4.6 hours before the alert went out and 70 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
- 368 J/kg
- Mixed-layer CIN
- -22 J/kg
- Mixed-layer LCL
- 754 m above ground
- 0-6 km bulk shear
- 13 kt
- 0-1 km storm-relative helicity
- 40 m²/s²
- 0-3 km storm-relative helicity
- 30 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
389
ACUS11 KWNS 161636
SWOMCD
SPC MCD 161636
FLZ000-161830-
Mesoscale Discussion 1533
NWS Storm Prediction Center Norman OK
1136 AM CDT Mon Aug 16 2021
Areas affected...The Apalachee Bay Coast
Concerning...Tornado Watch 441...
Valid 161636Z - 161830Z
The severe weather threat for Tornado Watch 441 continues.
SUMMARY...Rain bands with embedded thunderstorms will continue to
move northward into the Apalachee Bay coastal areas over the next
1-2 hours. The threat for brief waterspouts and/or tornadoes should
correspondingly increase through the early afternoon.
DISCUSSION...Tropical storm Fred continues to gradually shift
northward towards the FL panhandle. To the east of the center
circulation, persistent rain bands continue to feature embedded
thunderstorms thanks to a combination of low-level confluence over
Apalachee Bay and warm theta-e advection off the FL peninsula. VWP
observations from KTLH have shown strengthening flow in the lowest
1-2 km over the past hour as Fred's stronger wind field shifts
north. Consequently, low-level helicity has increased and is
supporting weak rotation in thunderstorms within the rain bands.
Recent RAP analyses support this trend and show favorable ESRH
beginning to overspread much of the Apalachee Bay coastal areas. As
a result, the potential for brief waterspouts and tornadoes is
expected to increase along the coast over the next few hours as the
rain bands begin to move onshore.
..Moore.. 08/16/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TAE...
LAT...LON 29638516 29978500 30188460 30278422 30118368 29968346
29788331 29568333 29488345 29538358 29698373 29878389
29928411 29768436 29638465 29498492 29488512 29638516SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 16, 6:26 AM EDT | Mesoscale Discussion | SPC | Franklin | 3 hr |
| Aug 16, 8:33 AM EDT | Tornado Watch | SPC | Bay, Calhoun, Dixie, Franklin, Gadsden, Gulf and 8 more | 13 hr |
| Aug 16, 10:20 AM EDT | Mesoscale Discussion | SPC | Franklin, Wakulla | 115 min |
| Aug 16, 3:55 PM EDT | Mesoscale Discussion | SPC | Dixie, Gilchrist, Jefferson, Lafayette, Levy, Taylor | 2 hr |
| Aug 16, 7:26 PM EDT | Mesoscale Discussion | SPC | Bay, Calhoun, Franklin, Gadsden, Gulf, Jackson and 6 more | 64 min |
Nearby
Mesoscale 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.