Alert archive / South Carolina / Mesoscale Discussions in 2021

Mesoscale Discussion 1925

October 28, 20218 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Oct 28, 2021, 6:36 PM EDT for 8 counties in South Carolina. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Oct 28, 2021, 6:36 PM EDT (22:36 UTC)
Expired: Oct 28, 2021, 9:30 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Colleton County, SC, Dorchester County, SC, Georgetown County, SC, Horry County, SC, Williamsburg County, SC

The radar

The Wilmington radar (KLTX), 134 km from the middle of the area, began a volume at 22:38 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

Charleston AFB, SC (KCHS), launched 12:00Z, 10.6 hours before the alert went out and 55 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1425 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 130 m²/s²
0-3 km storm-relative helicity: 143 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

664 
ACUS11 KWNS 282236
SWOMCD
SPC MCD 282236 
NCZ000-SCZ000-290130-

Mesoscale Discussion 1925
NWS Storm Prediction Center Norman OK
0536 PM CDT Thu Oct 28 2021

Areas affected...southern and eastern South Carolina into southern
coastal North Carolina

Concerning...Severe potential...Watch unlikely 

Valid 282236Z - 290130Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated cells may affect eastern South Carolina over the
next few hours, and eventually into eastern North Carolina later
this evening. A conditional threat of a tornado will exist.

DISCUSSION...Surface observations show a warm front extending from
eastern GA into southern SC, with low 70s F dewpoints south of the
boundary. Although temperatures aloft are warm, this magnitude of
moisture will lead to sufficient CAPE to support convection.
Low-level shear is quite favorable for rotation assuming a storm
moves into this environment, with 0-1 km values near 300 m2/s2
immediately near the warm front.

Ongoing convection currently over southern SC will need to be
monitored as it potentially translates up the coastal counties this
evening. Additional cells are possible as well due to lift from warm
advection. A brief tornado is conditionally possible, but expected
coverage of severe may not warrant a watch.

..Jewell/Grams.. 10/28/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ILM...CHS...CAE...

LAT...LON   32558000 32328037 32138055 32148074 32408089 32848085
            33777969 34157920 34217877 34157841 34057831 33877831
            33797862 33527896 33147913 32558000

Nearby

Mesoscale Discussions in South Carolina, 2021 Every 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.