Alert archive / Virginia / Mesoscale Discussions in 2015

Mesoscale Discussion 1803

September 12, 20155 counties in Maryland; 11 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Sep 12, 2015, 10:02 AM EDT for 5 counties in Maryland; 11 counties in Virginia. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Sep 12, 2015, 10:02 AM EDT (14:02 UTC)
Expired: Sep 12, 2015, 12:00 PM EDT
In force: 118 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Accomack County, VA, Essex County, VA, Gloucester County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, Northampton County, VA, Northumberland County, VA, Richmond County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 117 km from the middle of the area, began a volume at 14:03 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 2.0 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.

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: 104 J/kg
Mixed-layer CIN: -40 J/kg
Mixed-layer LCL: 857 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 38 m²/s²
0-3 km storm-relative helicity: 98 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 12, 6:33 AM EDT	Mesoscale Discussion	SPC	Saint Mary's	117 min
Sep 12, 2:28 PM EDT	Mesoscale Discussion	SPC	Dorchester, Saint Mary's, Somerset, Wicomico, Worcester	2 hr

Nearby

Mesoscale Discussions in Virginia, 2015 Mesoscale Discussions in Maryland, 2015 Every mesoscale discussion in 2015

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.