Alert archive / Virginia / Mesoscale Discussions in 2015

Mesoscale Discussion 1502

July 21, 2015Saint Mary's County, Somerset County, Wicomico County, Maryland; 43 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Jul 21, 2015, 3:01 PM EDT for Saint Mary's County, Somerset County, Wicomico County, Maryland; 43 counties in Virginia. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Jul 21, 2015, 3:01 PM EDT (19:01 UTC)
Expired: Jul 21, 2015, 5:00 PM EDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 46 counties

Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Accomack County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Hopewell, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Richmond, VA, City of Williamsburg, VA, Culpeper County, VA, Essex County, VA, Gloucester County, VA, Goochland County, VA, Hanover County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Louisa County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Orange County, VA, Powhatan County, VA, Prince George County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 105 km from the middle of the area, began a volume at 19:05 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.0 hours before the alert went out and 122 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: 339 J/kg
Mixed-layer CIN: -56 J/kg
Mixed-layer LCL: 1228 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: -36 m²/s²
0-3 km storm-relative helicity: 74 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.2

Open this sounding in Storm Lab

The text

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

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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.