Alert archive / New Jersey / Mesoscale Discussions in 2011

Mesoscale Discussion 1913

August 9, 20119 counties in New Jersey; 5 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Aug 9, 2011, 12:48 PM EDT for 9 counties in New Jersey; 5 counties in Pennsylvania. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Aug 9, 2011, 12:48 PM EDT (16:48 UTC)
Expired: Aug 9, 2011, 1:45 PM EDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Somerset County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 48 km from the middle of the area, began a volume at 16:51 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 755Aug 9, 4:20 PM EDT

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 4.8 hours before the alert went out and 135 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: 210 J/kg
Mixed-layer CIN: -77 J/kg
Mixed-layer LCL: 1178 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 96 m²/s²
0-3 km storm-relative helicity: 173 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

Open this sounding in Storm Lab

The text

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

748 
ACUS11 KWNS 091648
SWOMCD
SPC MCD 091648 
NJZ000-NYZ000-PAZ000-DEZ000-091745-

MESOSCALE DISCUSSION 1913
NWS STORM PREDICTION CENTER NORMAN OK
1148 AM CDT TUE AUG 09 2011

AREAS AFFECTED...SERN PA...NRN DE...SRN/CNTRL NJ

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 091648Z - 091745Z

INITIAL STORMS MOVING THROUGH THE UPPER MID ATLANTIC WILL PRODUCE
ISOLATED STRONG TO SEVERE WINDS AND PERHAPS A TORNADO. ALTHOUGH A WW
IS NOT EXPECTED AT THIS TIME...ONE MAY BECOME NECESSARY LATER THIS
AFTERNOON.

A FEW THUNDERSTORMS HAVE DEVELOPED EARLY THIS AFTERNOON ACROSS
PORTIONS OF THE UPPER MID ATLANTIC IN ADVANCE OF A NEGATIVELY TILTED
SHORT WAVE TROUGH ACROSS SRN/ERN ONTARIO SEWD INTO CNTRL VA. A WEAK
VORT MAX IS OBSERVED ON WV IMAGERY OVER WRN/CNTRL NY...AND INTO
CNTRL NY...PROVIDING SUBTLE UPPER FORCING FOR CONTINUED CONVECTIVE
DEVELOPMENT. BROAD WARM ADVECTION REGIME MAY CONTINUE TO SUPPORT THE
DEVELOPMENT OF THUNDERSTORMS THROUGHOUT THE EARLY AFTERNOON...THOUGH
CLOUD COVER IS LIMITING DESTABILIZATION AT THE MOMENT. 12Z IAD AND
APG SOUNDINGS REFLECT POOR LOW/MID LEVEL LAPSE RATES...WHICH MAY
INITIALLY ONLY SUPPORT ISOLATED STRONG TO SEVERE DEVELOPMENT UNTIL
LATER THIS AFTERNOON. HOWEVER...RECENT DOVER VAD WIND PROFILE DATA
SHOWS NEAR 300 M2/S2 0-3 KM SRH...WHICH WILL BE SUPPORTIVE OF
OCCASIONALLY ROTATING STORMS CAPABLE OF DMGG WINDS AND PERHAPS AN
ISOLATED TORNADO. DUE TO THE INITIALLY ISOLATED NATURE...A WW IS NOT
ANTICIPATED AT THIS TIME...BUT MAY BECOME NECESSARY LATER THIS
AFTERNOON.

..HURLBUT.. 08/09/2011

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

ATTN...WFO...OKX...PHI...

LAT...LON   40367400 39577431 39677549 39947589 40477559 40747512
            40637441 40367400

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 9, 3:05 PM EDT	Mesoscale Discussion	SPC	Bergen, Burlington, Camden, Essex, Gloucester, Hudson and 10 more	55 min
Aug 9, 4:16 PM EDT	Severe Thunderstorm Watch	SPC	Bergen, Burlington, Camden, Essex, Gloucester, Hudson and 8 more	5 hr
Aug 9, 7:07 PM EDT	Mesoscale Discussion	SPC	Burlington, Camden, Cumberland, Gloucester, Hunterdon, Mercer and 6 more	83 min
Aug 9, 6:56 PM EDT	Severe Thunderstorm Watch	SPC	Crawford, Erie, Lawrence, Mercer	5 hr

Nearby

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