Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 796

May 21, 2004Charles County, Saint Mary's County, Maryland; 12 counties in North Carolina; 79 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at May 21, 2004, 12:28 PM EDT for Charles County, Saint Mary's County, Maryland; 12 counties in North Carolina; 79 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 21, 2004, 12:28 PM EDT (16:28 UTC)
Expired: May 21, 2004, 2:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 93 counties

Charles County, MD, Saint Mary's County, MD, Bertie County, NC, Camden County, NC, Chowan County, NC, Currituck County, NC, Gates County, NC, Halifax County, NC, Hertford County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Tyrrell County, NC, Washington County, NC, Accomack County, VA, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Bedford County, VA, Botetourt County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Hopewell, VA, City of Lexington, VA, City of Lynchburg, 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 Roanoke, VA, City of Salem, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Waynesboro, VA, City of Williamsburg, VA, Craig County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fluvanna County, VA, Gloucester County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Halifax 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, Lunenburg County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Richmond County, VA, Roanoke County, VA, Rockbridge County, VA, Southampton 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), 47 km from the middle of the area, began a volume at 16:29 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 233May 21, 1:00 PM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 4.5 hours before the alert went out and 181 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: 532 J/kg
Mixed-layer CIN: -66 J/kg
Mixed-layer LCL: 845 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: -50 m²/s²
0-3 km storm-relative helicity: 11 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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
May 21, 8:34 AM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Carroll, Charles, Frederick, Howard and 4 more	86 min
May 21, 5:31 PM EDT	Mesoscale Discussion	SPC	Allegany, Frederick, Garrett, Washington	89 min
May 21, 6:35 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Carroll, Charles, Frederick, Garrett, Howard and 3 more	4 hr
May 21, 1:00 PM EDT	Severe Thunderstorm Watch	SPC	Camden, Currituck, Gates, Hertford, Northampton, Pasquotank	7 hr
May 21, 4:30 PM EDT	Mesoscale Discussion	SPC	Camden, Chowan, Currituck, Gates, Hertford, Pasquotank and 1 more	2 hr

Nearby

Mesoscale Discussions in Virginia, 2004 Mesoscale Discussions in North Carolina, 2004 Mesoscale Discussions in Maryland, 2004 Every mesoscale discussion in 2004

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.