Alert archive / North Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 1544
The Storm Prediction Center issued this mesoscale discussion at Aug 17, 2021, 12:35 PM EDT for 15 counties in North Carolina; 14 counties in South Carolina. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Aug 17, 2021, 12:35 PM EDT (16:35 UTC)
- Expired
- Aug 17, 2021, 2:00 PM EDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 444
All 29 counties
Alexander County, NC, Cabarrus County, NC, Catawba County, NC, Cleveland County, NC, Davie County, NC, Forsyth County, NC, Gaston County, NC, Iredell County, NC, Lincoln County, NC, Mecklenburg County, NC, Rowan County, NC, Rutherford County, NC, Surry County, NC, Wilkes County, NC, Yadkin County, NC, Abbeville County, SC, Anderson County, SC, Cherokee County, SC, Chester County, SC, Edgefield County, SC, Greenville County, SC, Greenwood County, SC, Laurens County, SC, McCormick County, SC, Newberry County, SC, Saluda County, SC, Spartanburg County, SC, Union County, SC, York County, SC
The radar
The Greer radar (KGSP), 83 km from the middle of the area, began a volume at 16:35 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
Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 4.6 hours before the alert went out and 166 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
- 522 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 593 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 77 m²/s²
- 0-3 km storm-relative helicity
- 99 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.9
The text
As transmitted.
042
ACUS11 KWNS 171636
SWOMCD
SPC MCD 171635
NCZ000-SCZ000-GAZ000-171800-
Mesoscale Discussion 1544
NWS Storm Prediction Center Norman OK
1135 AM CDT Tue Aug 17 2021
Areas affected...western Carolinas
Concerning...Tornado Watch 444...
Valid 171635Z - 171800Z
The severe weather threat for Tornado Watch 444 continues.
SUMMARY...The risk for a tornado will likely focus through the
midday and into the early afternoon in two areas: 1) occasional
strengthening of storm-scale rotation in the more prominent band
east of the circulation center, and 2) with developing convection
over west-central NC moving northwestward into a baroclinic zone.
DISCUSSION...Midday surface analysis indicates a sharpening
baroclinic zone over the western Carolinas in a north-south line
from near/immediately east of Spartanburg, SC northward to 35 mi
northeast of Hickory, NC. Temperatures east of the boundary have
warmed into the upper 70s over SC Piedmont and slightly warmer
farther north into NC with lower 80s observed near Charlotte. A
very moisture rich airmass featuring mid 70s surface dewpoints in
combination with some heating will yield sufficient buoyancy for
sustained strong updraft development for a couple of storms. It
seems the most vorticity rich low levels will continue to be near
the boundary. The Greer, SC 88D VAD shows an enlarged hodograph
with 100-150 m2/s2 0-1 km SRH when accounting for observed storm
motions. Given the adequate buoyancy/SRH in place, a couple of
supercells with an occasional tornado threat seems probable through
the early and into the mid afternoon.
..Smith.. 08/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RAH...RNK...CAE...GSP...
LAT...LON 34458283 36298110 36468073 36118021 35628026 33368203
34458283SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 10:42 AM EDT | Tornado Watch | SPC | Alexander, Avery, Buncombe, Burke, Cabarrus, Caldwell and 20 more | 8 hr |
| Aug 17, 1:06 PM EDT | Tornado Watch | SPC | Alleghany, Ashe, Rockingham, Stokes, Surry, Watauga and 2 more | 5 hr |
| Aug 17, 3:25 PM EDT | Mesoscale Discussion | SPC | Buncombe, Burke, Cleveland, Gaston, Henderson, Lincoln and 4 more | 2 hr |
| Aug 17, 5:55 PM EDT | Mesoscale Discussion | SPC | Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 28 more | 65 min |
| Aug 17, 6:28 PM EDT | Tornado Watch | SPC | Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 24 more | 10 hr |
| Aug 17, 8:22 AM EDT | Mesoscale Discussion | SPC | Abbeville, Anderson, Edgefield, Greenwood, McCormick | 113 min |
Nearby
Mesoscale Discussions in North Carolina, 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.