Alert archive / North Carolina / Mesoscale Discussions in 2020

Mesoscale Discussion 1702

September 17, 20206 counties in North Carolina; Horry County, South Carolina

The Storm Prediction Center issued this mesoscale discussion at Sep 17, 2020, 6:54 PM EDT for 6 counties in North Carolina; Horry County, South Carolina. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Sep 17, 2020, 6:54 PM EDT (22:54 UTC)
Expired: Sep 17, 2020, 9:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Tornado watch 493

Counties Bladen County, NC, Brunswick County, NC, Columbus County, NC, New Hanover County, NC, Onslow County, NC, Pender County, NC, Horry County, SC

The radar

The Wilmington radar (KLTX), 41 km from the middle of the area, began a volume at 22:59 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

Newport, NC (KMHX), launched 12:00Z, 10.9 hours before the alert went out and 126 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: 226 J/kg
Mixed-layer CIN: -45 J/kg
Mixed-layer LCL: 646 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 95 m²/s²
0-3 km storm-relative helicity: 148 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 17, 10:27 AM EDT	Mesoscale Discussion	SPC	Cumberland, Hoke, Robeson, Scotland	2 hr
Sep 17, 2:33 PM EDT	Mesoscale Discussion	SPC	Bladen, Columbus, Cumberland, Duplin, Lenoir, Robeson and 1 more	117 min
Sep 17, 3:06 PM EDT	Tornado Watch	SPC	Bladen, Brunswick, Carteret, Columbus, Craven, Cumberland and 13 more	8 hr
Sep 17, 10:20 AM EDT	Tornado Watch	SPC	Aiken, Bamberg, Barnwell, Calhoun, Chesterfield, Clarendon and 15 more	8 hr

Nearby

Mesoscale Discussions in North Carolina, 2020 Mesoscale Discussions in South Carolina, 2020 Every mesoscale discussion in 2020

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.