Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 2147

September 7, 20114 counties in New Jersey; 6 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Sep 7, 2011, 3:36 PM EDT for 4 counties in New Jersey; 6 counties in Pennsylvania. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Sep 7, 2011, 3:36 PM EDT (19:36 UTC)
Expired: Sep 7, 2011, 5:00 PM EDT
In force: 84 min
Issued by: the Storm Prediction Center

Counties Burlington County, NJ, Camden County, NJ, Mercer County, NJ, Middlesex County, NJ, Berks County, PA, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 70 km from the middle of the area, began a volume at 19:39 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

Brookhaven, NY (KOKX), launched 12:00Z, 7.6 hours before the alert went out and 218 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: 1 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 428 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 228 m²/s²
0-3 km storm-relative helicity: 270 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

802 
ACUS11 KWNS 071937
SWOMCD
SPC MCD 071936
NJZ000-PAZ000-DEZ000-072100-

MESOSCALE DISCUSSION 2147
NWS STORM PREDICTION CENTER NORMAN OK
0236 PM CDT WED SEP 07 2011

AREAS AFFECTED...SERN AND EAST CENTRAL PA INTO PARTS OF CENTRAL NJ

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 071936Z - 072100Z

AN ISOLATED THREAT FOR A STRONG WIND GUST AND/OR A TORNADO CANNOT BE
RULED OUT THE REST OF THE AFTERNOON FROM SERN PA INTO CENTRAL NJ.
GIVEN THE LIMITED SPATIAL EXTENT AND OVERALL THREAT CONCERN...A WW
IS NOT ANTICIPATED.

AFTERNOON MESOANALYSES INDICATED A WARM FRONT HAD MOVED INTO SERN PA
AND EXTENDED NEWD FROM LANCASTER TO NRN BUCKS COUNTIES PA AND THEN
ENEWD THROUGH CENTRAL NJ TO OFFSHORE THE SRN LONG ISLAND COAST.
STRONG SURFACE HEATING AND DEWPOINTS IN THE LOWER-MID 70S ARE
RESULTING IN MLCAPE OF 1000-1200 J/KG WITHIN THE WARM SECTOR.  DEEP
UNIDIRECTIONAL FLOW/SHEAR VECTORS ARE SUPPORTING PRIMARILY
LINES/SHORT BOWING SEGMENTS AS INDICATED BY REGIONAL RADAR IMAGERY
MOVING NEWD THROUGH SERN PA AT 1925Z.  BACKED SURFACE WINDS IN THE
WARM SECTOR AND INVOF THE WARM FRONT ARE ALSO RESULTING IN ENHANCED
LOW LEVEL SHEAR /EFFECTIVE SRH UP TO 200 M2 PER S2/ SUPPORTING LOW
LEVEL STORM ROTATION AS HAS BEEN NOTED IN A STORM OR TWO THIS
AFTERNOON OVER SERN PA.

..PETERS.. 09/07/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...CTP...

LAT...LON   39767592 40097588 40467595 40537502 40457428 40217412
            39867431 39777509 39707566 39767592

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in New Jersey, 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.