Alert archive / Pennsylvania / Mesoscale Discussions in 2015

Mesoscale Discussion 803

May 27, 20157 states

The Storm Prediction Center issued this mesoscale discussion at May 27, 2015, 12:21 PM EDT for 7 states. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued: May 27, 2015, 12:21 PM EDT (16:21 UTC)
Expired: May 27, 2015, 1:15 PM EDT
In force: 54 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 76 counties

Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, City of Baltimore, 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, Washington County, MD, Bergen County, NJ, Camden County, NJ, Essex County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Delaware County, NY, Dutchess County, NY, Orange County, NY, Putnam County, NY, Rockland 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, Susquehanna County, PA, Wayne County, PA, Wyoming County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Manassas, VA, City of Manassas Park, VA, Clarke County, VA, Fairfax County, VA, Loudoun County, VA, Prince William County, VA, Warren County, VA, Jefferson County, WV

The radar

The Philadelphia radar (KDIX), 130 km from the middle of the area, began a volume at 16:21 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 227May 27, 12:55 PM EDT

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 4.4 hours before the alert went out and 160 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: 428 J/kg
Mixed-layer CIN: -59 J/kg
Mixed-layer LCL: 589 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 78 m²/s²
0-3 km storm-relative helicity: 81 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

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 27, 12:54 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	6 hr
May 27, 2:59 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	2 hr
May 27, 4:49 PM EDT	Mesoscale Discussion	SPC	Bergen, Burlington, Camden, Essex, Gloucester, Hudson and 11 more	86 min
May 27, 11:50 AM EDT	Mesoscale Discussion	SPC	Albany, Clinton, Columbia, Delaware, Essex, Fulton and 11 more	85 min

Nearby

Mesoscale Discussions in Pennsylvania, 2015 Mesoscale Discussions in Maryland, 2015 Mesoscale Discussions in New Jersey, 2015 Every mesoscale discussion in 2015

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.