Alert archive / Virginia / Mesoscale Discussions in 2009

Mesoscale Discussion 700

May 4, 200921 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at May 4, 2009, 3:26 PM EDT for 21 counties in Virginia. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: May 4, 2009, 3:26 PM EDT (19:26 UTC)
Expired: May 4, 2009, 4:30 PM EDT
In force: 64 min
Issued by: the Storm Prediction Center

All 21 counties

Charles City County, VA, Chesterfield County, VA, City of Colonial Heights, 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 Virginia Beach, VA, City of Williamsburg, VA, Gloucester County, VA, Henrico County, VA, James City County, VA, Mathews County, VA, New Kent County, VA, Northampton County, VA, Prince George County, VA, Surry County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 58 km from the middle of the area, began a volume at 19:27 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, 7.4 hours before the alert went out and 127 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 474 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 203 m²/s²
0-3 km storm-relative helicity: 228 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 4, 12:03 PM EDT	Mesoscale Discussion	SPC	Amelia, Brunswick, Charles City, Chesterfield, Dinwiddie, Gloucester and 33 more	57 min
May 4, 12:29 PM EDT	Tornado Watch	SPC	Accomack, Amelia, Appomattox, Bedford, Brunswick, Campbell and 49 more	5 hr
May 4, 1:30 PM EDT	Severe Thunderstorm Watch	SPC	Isle of Wight, Southampton, City of Chesapeake, City of Franklin, City of Norfolk, City of Portsmouth and 2 more	9 hr

Nearby

Mesoscale Discussions in Virginia, 2009 Every mesoscale discussion in 2009

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.