Alert archive / Pennsylvania / Mesoscale Discussions in 2012

Mesoscale Discussion 1965

September 18, 20125 states

The Storm Prediction Center issued this mesoscale discussion at Sep 18, 2012, 1:56 PM EDT for 5 states. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued
Sep 18, 2012, 1:56 PM EDT (17:56 UTC)
Expired
Sep 18, 2012, 3:00 PM EDT
In force
64 min
Issued by
the Storm Prediction Center
All 60 counties

Kent County, DE, New Castle County, DE, Sussex County, DE, Cecil County, MD, Harford 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, Kings County, NY, New York County, NY, Orange County, NY, Richmond County, NY, Rockland 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, Union County, PA, Wayne County, PA, Wyoming County, PA, York County, PA

The radar

The Philadelphia radar (KDIX), 111 km from the middle of the area, began a volume at 17:58 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 5.9 hours before the alert went out and 75 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, Phillips Aaf/Abe, MD at 12:00Z on 2012-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 330 joules per kilogram.LCLLFCEL10008507005003002001001 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, Phillips Aaf/Abe, MD at 12:00Z on 2012-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 265 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
330 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
519 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
265 m²/s²
0-3 km storm-relative helicity
275 m²/s²
Significant tornado parameter
0.4
Supercell composite
2.3

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, 11:19 AM EDTMesoscale DiscussionSPCKent, New Castle86 min
Sep 18, 12:10 PM EDTTornado WatchSPCKent, New Castle, Sussex9 hr
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

Nearby

Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in New Jersey, 2012Mesoscale Discussions in New York, 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.