Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 2030

August 21, 20118 states

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2011, 11:54 AM EDT for 8 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 21, 2011, 11:54 AM EDT (15:54 UTC)
Expired: Aug 21, 2011, 2:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 123 counties

Kent County, DE, New Castle County, DE, Sussex County, DE, Berkshire County, MA, Allegany County, MD, 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, Talbot County, MD, Washington County, MD, Wicomico County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Albany County, NY, Bronx County, NY, Columbia County, NY, Dutchess County, NY, Greene County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Orange County, NY, Putnam County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Sullivan County, NY, Ulster County, NY, Westchester County, NY, Adams County, PA, Bedford 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, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Wayne County, PA, York County, PA, Arlington County, VA, Caroline County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Hampshire County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Dover AFB radar (KDOX), 148 km from the middle of the area, began a volume at 15:57 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, 3.9 hours before the alert went out and 158 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: 1589 J/kg
Mixed-layer CIN: -99 J/kg
Mixed-layer LCL: 969 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 131 m²/s²
0-3 km storm-relative helicity: 125 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 4.9

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
Aug 21, 12:52 PM EDT	Severe Thunderstorm Watch	SPC	Greater Bridgeport Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region	8 hr
Aug 21, 1:20 PM EDT	Severe Thunderstorm Watch	SPC	Capitol Planning Region, Northwest Hills Planning Region, Northeastern Connecticut Planning Region	8 hr
Aug 21, 3:05 PM EDT	Mesoscale Discussion	SPC		55 min
Aug 21, 7:12 PM EDT	Mesoscale Discussion	SPC		63 min
Aug 21, 2:06 PM EDT	Severe Thunderstorm Watch	SPC	Dorchester, Somerset, Wicomico, Worcester	7 hr
Aug 21, 6:42 PM EDT	Mesoscale Discussion	SPC	Somerset	63 min
Aug 21, 4:34 PM EDT	Mesoscale Discussion	SPC	Berkshire	116 min
Aug 21, 1:45 PM EDT	Mesoscale Discussion	SPC	Amelia, Appomattox, Brunswick, Buckingham, Campbell, Charlotte and 22 more	90 min
Aug 21, 1:43 PM EDT	Mesoscale Discussion	SPC	Calhoun, Doddridge, Gilmer, Jackson, Mason, Pleasants and 4 more	62 min

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

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.