Alert archive / Virginia / Mesoscale Discussions in 2009

Mesoscale Discussion 783

May 9, 200925 counties in North Carolina; 34 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at May 9, 2009, 4:30 PM EDT for 25 counties in North Carolina; 34 counties in Virginia. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued
May 9, 2009, 4:30 PM EDT (20:30 UTC)
Expired
May 9, 2009, 6:00 PM EDT
In force
90 min
Issued by
the Storm Prediction Center
All 59 counties

Alamance County, NC, Cabarrus County, NC, Caswell County, NC, Catawba County, NC, Chatham County, NC, Davidson County, NC, Davie County, NC, Durham County, NC, Forsyth County, NC, Granville County, NC, Guilford County, NC, Iredell County, NC, Lincoln County, NC, Mecklenburg County, NC, Montgomery County, NC, Moore County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Stanly County, NC, Stokes County, NC, Vance County, NC, Yadkin County, NC, Amelia County, VA, Appomattox County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charlotte County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Danville, VA, City of Hopewell, VA, City of Martinsville, VA, City of Petersburg, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fluvanna County, VA, Goochland County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, King and Queen County, VA, King William County, VA, Louisa County, VA, Lunenburg County, VA, Mecklenburg County, VA, New Kent County, VA, Nottoway County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Richmond County, VA

The radar

The Raleigh/Durham radar (KRAX), 109 km from the middle of the area, began a volume at 20:34 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.

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 8.5 hours before the alert went out and 86 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, Roanoke, VA at 12:00Z on 2009-05-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 589 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, Roanoke, VA at 12:00Z on 2009-05-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 22 square meters per square second.19395878Sfc1 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
589 J/kg
Mixed-layer CIN
-21 J/kg
Mixed-layer LCL
666 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
22 m²/s²
0-3 km storm-relative helicity
33 m²/s²
Significant tornado parameter
0.1
Supercell composite
0.6

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
May 8, 8:30 PM EDTMesoscale DiscussionSPCAlexander, Alleghany, Ashe, Avery, Buncombe, Burke and 19 more90 min
May 8, 10:01 PM EDTTornado WatchSPCCaswell, Rockingham, Stokes4 hr
May 8, 11:37 PM EDTMesoscale DiscussionSPCAlleghany, Ashe, Forsyth, Rockingham, Stokes, Surry and 3 more53 min
May 9, 12:51 AM EDTMesoscale DiscussionSPCCaswell, Edgecombe, Franklin, Gates, Granville, Halifax and 7 more84 min
May 9, 12:47 PM EDTMesoscale DiscussionSPCAlamance, Alexander, Burke, Cabarrus, Caldwell, Caswell and 32 more118 min
May 9, 1:17 PM EDTSevere Thunderstorm WatchSPCAlamance, Alexander, Anson, Burke, Cabarrus, Caldwell and 36 more8 hr
May 9, 5:58 PM EDTMesoscale DiscussionSPCBertie, Camden, Chatham, Chowan, Durham, Edgecombe and 20 more62 min
May 9, 6:25 PM EDTSevere Thunderstorm WatchSPCBeaufort, Bertie, Camden, Carteret, Chowan, Craven and 31 more4 hr
May 9, 1:07 AM EDTTornado WatchSPCAmelia, Brunswick, Charles City, Chesterfield, Cumberland, Dinwiddie and 39 more4 hr

Nearby

Mesoscale Discussions in Virginia, 2009Mesoscale Discussions in North Carolina, 2009Every 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.