Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 1960

September 18, 20129 states

The Storm Prediction Center issued this mesoscale discussion at Sep 18, 2012, 11:19 AM EDT for 9 states. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued
Sep 18, 2012, 11:19 AM EDT (15:19 UTC)
Expired
Sep 18, 2012, 12:45 PM EDT
In force
86 min
Issued by
the Storm Prediction Center
All 185 counties

Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Alamance County, NC, Caswell County, NC, Chatham County, NC, Cumberland County, NC, Durham County, NC, Edgecombe County, NC, Franklin County, NC, Granville County, NC, Greene County, NC, Guilford County, NC, Halifax County, NC, Harnett County, NC, Hertford County, NC, Hoke County, NC, Johnston County, NC, Lee County, NC, Montgomery County, NC, Moore County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Richmond County, NC, Robeson County, NC, Rockingham County, NC, Sampson County, NC, Scotland County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wayne County, NC, Wilson County, NC, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Morris County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, Albany County, NY, Broome County, NY, Chenango County, NY, Delaware County, NY, Fulton County, NY, Greene County, NY, Montgomery County, NY, Orange County, NY, Otsego County, NY, Saratoga County, NY, Schenectady County, NY, Schoharie County, NY, Sullivan County, NY, Ulster County, NY, Adams County, PA, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Monroe County, PA, Montgomery County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Wayne County, PA, Wyoming County, PA, York County, PA, Marlboro County, SC, Albemarle County, VA, Amelia County, VA, Appomattox County, VA, Arlington 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 Alexandria, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Fairfax, VA, City of Falls Church, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Newport News, VA, City of Petersburg, VA, City of Richmond, VA, City of Suffolk, VA, City of Williamsburg, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier 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, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA, Jefferson County, WV

The radar

The Sterling radar (KLWX), 50 km from the middle of the area, began a volume at 15:20 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 3.3 hours before the alert went out and 42 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, Washington/Dulle, VA at 12:00Z on 2012-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 371 joules per kilogram.LCLEL10008507005003002001001 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, Washington/Dulle, VA at 12:00Z on 2012-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 322 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
371 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
454 m above ground
0-6 km bulk shear
56 kt
0-1 km storm-relative helicity
322 m²/s²
0-3 km storm-relative helicity
403 m²/s²
Significant tornado parameter
0.9
Supercell composite
4.2

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
Sep 18, 11:14 AM EDTMesoscale DiscussionSPCNew Castle91 min
Sep 18, 12:10 PM EDTTornado WatchSPCKent, New Castle, Sussex9 hr
Sep 18, 1:56 PM EDTMesoscale DiscussionSPCKent, New Castle, Sussex64 min
Sep 18, 4:21 PM EDTMesoscale DiscussionSPCKent, New Castle, Sussex114 min
Sep 18, 6:08 PM EDTMesoscale DiscussionSPCKent, Sussex67 min
Sep 18, 6:15 PM EDTMesoscale DiscussionSPCKent, Sussex30 min
Sep 18, 8:49 AM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Calvert, Carroll, Charles, Frederick and 8 more116 min
Sep 18, 10:54 AM EDTTornado WatchSPCAnne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 11 more9 hr
Sep 18, 1:27 PM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 10 more63 min
Sep 18, 3:52 PM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Calvert, Charles, Dorchester, Howard and 7 more113 min
Sep 18, 12:57 PM EDTMesoscale DiscussionSPCAlbany, Broome, Chemung, Chenango, Columbia, Cortland and 11 more93 min
Sep 18, 1:21 PM EDTTornado WatchSPCBroome, Chenango, Cortland, Delaware, Madison, Oneida and 4 more5 hr
Sep 18, 2:10 PM EDTMesoscale DiscussionSPCClinton, Essex, Franklin, Fulton, Hamilton, Herkimer and 6 more95 min
Sep 18, 3:26 PM EDTMesoscale DiscussionSPCAlbany, Columbia, Dutchess, Essex, Franklin, Fulton and 11 more34 min
Sep 18, 3:38 PM EDTTornado WatchSPCAlbany, Columbia, Dutchess, Fulton, Greene, Hamilton and 13 more8 hr
Sep 18, 7:42 PM EDTMesoscale DiscussionSPCBronx, Kings, Nassau, Putnam, Queens, Suffolk and 1 more63 min
Sep 17, 8:14 PM EDTMesoscale DiscussionSPCCherokee, Clay, Graham, Haywood, Henderson, Jackson and 4 more2 hr
Sep 18, 12:23 AM EDTMesoscale DiscussionSPCAlexander, Buncombe, Burke, Cabarrus, Caldwell, Catawba and 14 more97 min
Sep 18, 9:45 AM EDTTornado WatchSPCAlamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more8 hr
Sep 18, 11:35 AM EDTMesoscale DiscussionSPCUnion85 min
Sep 18, 1:00 PM EDTTornado WatchSPCBeaufort, Carteret, Craven, Dare, Duplin, Greene and 9 more5 hr
Sep 18, 1:21 PM EDTMesoscale DiscussionSPCAlamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more84 min
Sep 18, 4:11 PM EDTMesoscale DiscussionSPCAlamance, Anson, Beaufort, Carteret, Chatham, Craven and 40 more94 min
Sep 17, 10:21 PM EDTMesoscale DiscussionSPCAbbeville, Anderson, McCormick, Oconee, Pickens84 min
Sep 18, 9:39 AM EDTMesoscale DiscussionSPCAllendale, Bamberg, Barnwell, Beaufort, Hampton, Jasper66 min

Nearby

Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in Pennsylvania, 2012Every mesoscale discussion in 2012

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.