Alert archive / Pennsylvania / Mesoscale Discussions in 2014

Mesoscale Discussion 1689

September 6, 20146 states

The Storm Prediction Center issued this mesoscale discussion at Sep 6, 2014, 6:58 PM EDT for 6 states. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Sep 6, 2014, 6:58 PM EDT (22:58 UTC)
Expired: Sep 6, 2014, 8:30 PM EDT
In force: 92 min
Issued by: the Storm Prediction Center

All 66 counties

Kent County, DE, New Castle County, DE, Sussex 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, 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, Talbot County, MD, Washington County, MD, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, Adams County, PA, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Perry County, PA, Philadelphia County, PA, Schuylkill 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, Fairfax County, VA, Loudoun County, VA, Prince William County, VA, Berkeley County, WV, Jefferson County, WV

The radar

The Dover AFB radar (KDOX), 101 km from the middle of the area, began a volume at 22:57 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 nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 11.0 hours before the alert went out and 143 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: 1444 J/kg
Mixed-layer CIN: -42 J/kg
Mixed-layer LCL: 867 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 65 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
Sep 6, 2:07 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	7 hr
Sep 6, 4:20 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	85 min
Sep 6, 12:31 PM EDT	Mesoscale Discussion	SPC	Bergen, Essex, Hudson, Hunterdon, Mercer, Middlesex and 7 more	89 min
Sep 6, 1:22 PM EDT	Severe Thunderstorm Watch	SPC	Bergen, Essex, Hudson, Passaic, Union	8 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2014 Mesoscale Discussions in Maryland, 2014 Mesoscale Discussions in New Jersey, 2014 Every mesoscale discussion in 2014

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.