Alert archive / Virginia / Mesoscale Discussions in 2014

Mesoscale Discussion 1549

August 12, 2014Somerset County, Maryland; 15 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Aug 12, 2014, 2:39 PM EDT for Somerset County, Maryland; 15 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 12, 2014, 2:39 PM EDT (18:39 UTC)
Expired
Aug 12, 2014, 4:45 PM EDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
20%

Counties Somerset County, MD, Accomack County, VA, Charles City County, VA, City of Williamsburg, VA, Essex County, VA, Gloucester County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Richmond County, VA

The radar

The Norfolk radar (KAKQ), 104 km from the middle of the area, began a volume at 18:41 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, 6.7 hours before the alert went out and 82 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-pSkew-T log-p diagram, Wallops Is Stn, VA at 12:00Z on 2014-08-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 135 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Wallops Is Stn, VA at 12:00Z on 2014-08-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 61 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
135 J/kg
Mixed-layer CIN
-11 J/kg
Mixed-layer LCL
882 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
61 m²/s²
0-3 km storm-relative helicity
97 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.

IssuedProductOfficeCountiesLasted
Aug 12, 12:26 PM EDTMesoscale DiscussionSPCGarrett2 hr

Nearby

Mesoscale Discussions in Virginia, 2014Mesoscale Discussions in Maryland, 2014Every mesoscale discussion in 2014

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.