Alert archive / Florida / Mesoscale Discussions in 2021
Mesoscale Discussion 1177
The Storm Prediction Center issued this mesoscale discussion at Jul 7, 2021, 10:30 AM EDT for 9 counties in Florida; 9 counties in Georgia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 7, 2021, 10:30 AM EDT (14:30 UTC)
- Expired
- Jul 7, 2021, 12:30 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 341
Counties Baker County, FL, Bradford County, FL, Clay County, FL, Columbia County, FL, Duval County, FL, Hamilton County, FL, Nassau County, FL, Suwannee County, FL, Union County, FL, Brantley County, GA, Camden County, GA, Charlton County, GA, Clinch County, GA, Echols County, GA, Glynn County, GA, Pierce County, GA, Ware County, GA, Wayne County, GA
The radar
The Jacksonville radar (KJAX), 48 km from the middle of the area, began a volume at 14:33 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
Jacksonville, FL (KJAX), launched 12:00Z, 2.5 hours before the alert went out and 47 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
- 1540 J/kg
- Mixed-layer CIN
- -8 J/kg
- Mixed-layer LCL
- 838 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 103 m²/s²
- 0-3 km storm-relative helicity
- 144 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
561
ACUS11 KWNS 071430
SWOMCD
SPC MCD 071430
GAZ000-FLZ000-071630-
Mesoscale Discussion 1177
NWS Storm Prediction Center Norman OK
0930 AM CDT Wed Jul 07 2021
Areas affected...North FL Peninsula...southeast GA
Concerning...Tornado Watch 341...
Valid 071430Z - 071630Z
The severe weather threat for Tornado Watch 341 continues.
SUMMARY...The risk for a few tornadoes continues in association with
Tropical Storm Elsa.
DISCUSSION...At 1420z Tropical Storm Elsa was located just offshore
of the FL coast northwest of Cedar Key. A large area of rain
east/northeast of the center covered much of north FL, however
latest reflectivity data from KJAX shows a pronounced outer band
lifting north/northwest just north of the GA/FL border with recent
transient rotation, and more discrete cells/showers also over
southeast GA producing occasional short-lived low-level rotation.
Modifying the latest KJAX VAD for observed storm motion from the
southeast results in ESRH at or below 50 m2/s2, however latest RAP
forecast soundings suggest increasing ESRH values over the next few
hours as low-level winds increase as Elsa continues moving north.
Correspondingly, the risk for brief tornadoes may also increase over
the next few hours.
..Bunting.. 07/07/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CHS...JAX...TAE...
LAT...LON 30018145 29908228 29978309 30278321 30968296 31398262
31708203 31748189 31568154 31278136 30158136 30018145SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 6, 10:37 PM EDT | Tornado Watch | SPC | Alachua, Charlotte, Citrus, Collier, DeSoto, Gilchrist and 22 more | 9 hr |
| Jul 6, 11:59 PM EDT | Mesoscale Discussion | SPC | Charlotte, DeSoto, Hardee, Hillsborough | 2 hr |
| Jul 7, 3:03 AM EDT | Mesoscale Discussion | SPC | Charlotte, Citrus, DeSoto, Hardee, Hernando, Hillsborough and 5 more | 117 min |
| Jul 7, 5:42 AM EDT | Mesoscale Discussion | SPC | Alachua, Bradford, Charlotte, Citrus, Columbia, DeSoto and 19 more | 2 hr |
| Jul 7, 6:46 AM EDT | Tornado Watch | SPC | Baker, Bradford, Clay, Columbia, Duval, Hamilton and 4 more | 6 hr |
| Jul 7, 7:06 AM EDT | Mesoscale Discussion | SPC | Charlotte, Citrus, DeSoto, Hardee, Hernando, Highlands and 10 more | 54 min |
| Jul 7, 12:28 PM EDT | Mesoscale Discussion | SPC | Baker, Bradford, Clay, Columbia, Duval, Nassau and 1 more | 2 hr |
| Jul 7, 1:04 PM EDT | Tornado Watch | SPC | Baker, Bradford, Clay, Columbia, Duval, Hamilton and 3 more | 7 hr |
| Jul 7, 4:47 PM EDT | Mesoscale Discussion | SPC | Baker, Clay, Columbia, Duval, Nassau, Saint Johns and 1 more | 118 min |
| Jul 7, 6:12 PM EDT | Mesoscale Discussion | SPC | Brantley, Bryan, Camden, Chatham, Effingham, Evans and 6 more | 2 hr |
| Jul 7, 7:25 PM EDT | Tornado Watch | SPC | Bryan, Bulloch, Burke, Candler, Chatham, Effingham and 11 more | 11 hr |
Nearby
Mesoscale Discussions in Florida, 2021Mesoscale Discussions in Georgia, 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.