Alert archive / Pennsylvania / Mesoscale Discussions in 2012

Mesoscale Discussion 1764

August 14, 20125 states

The Storm Prediction Center issued this mesoscale discussion at Aug 14, 2012, 9:57 PM EDT for 5 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 14, 2012, 9:57 PM EDT (01:57 UTC)
Expired: Aug 15, 2012, 12:00 AM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 38 counties

Kent County, DE, New Castle County, DE, Baltimore County, MD, Carroll County, MD, Cecil County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Queen Anne's County, MD, Salem County, NJ, Broome County, NY, Chenango County, NY, Delaware County, NY, Otsego County, NY, Adams County, PA, Berks County, PA, Carbon County, PA, Chester County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Luzerne County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA, York County, PA

The radar

The Philadelphia radar (KDIX), 139 km from the middle of the area, began a volume at 01:59 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 2.0 hours before the alert went out and 222 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: 833 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 1690 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 32 m²/s²
0-3 km storm-relative helicity: 59 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
Aug 15, 2:34 PM EDT	Severe Thunderstorm Watch	SPC	Dorchester, Saint Mary's, Somerset, Wicomico, Worcester	6 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2012 Mesoscale Discussions in Maryland, 2012 Mesoscale Discussions in New York, 2012 Every 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.