Alert archive / New Jersey / Mesoscale Discussions in 2012

Mesoscale Discussion 1713

August 5, 20127 states

The Storm Prediction Center issued this mesoscale discussion at Aug 5, 2012, 6:38 PM EDT for 7 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 5, 2012, 6:38 PM EDT (22:38 UTC)
Expired: Aug 5, 2012, 8:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 39 counties

Kent County, DE, New Castle County, DE, Bristol County, MA, Norfolk County, MA, Caroline County, MD, Queen Anne's 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, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Union County, NJ, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Putnam County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Suffolk County, NY, Westchester County, NY, Philadelphia County, PA, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI

The radar

The Philadelphia radar (KDIX), 44 km from the middle of the area, began a volume at 22:38 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, 10.6 hours before the alert went out and 122 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: 2201 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 477 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 11 m²/s²
0-3 km storm-relative helicity: 3 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.

500 
ACUS11 KWNS 052238
SWOMCD
SPC MCD 052238 
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-060045-

MESOSCALE DISCUSSION 1713
NWS STORM PREDICTION CENTER NORMAN OK
0538 PM CDT SUN AUG 05 2012

AREAS AFFECTED...PORTIONS NJ...EXTREME ERN PA...ERN MD...DE...SERN
NY...CT...RI...MA.

CONCERNING...SEVERE THUNDERSTORM WATCH 564...

VALID 052238Z - 060045Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 564
CONTINUES.

SUMMARY...WW IS BEING EXTENDED EWD ACROSS PORTIONS NJ PER COORD
W/WFO PHI.  WW MAY BE CLEARED BEHIND PRIMARY QLCS...WHICH WAS
EVIDENT AT 2215Z FROM ANNE ARUNDEL COUNTY MD NNEWD ACROSS EXTREME
ERN PA TO ULSTER COUNTY NY.  ACTIVITY FARTHER W ACROSS WRN PA AND WV
SHOULD NOT REACH THIS REGION BEFORE SCHEDULED WW EXPIRATION
TIME...NOR SHOULD IT POSE ORGANIZED SVR THREAT BY THEN.

DISCUSSION...MEASURED GUSTS AT STATIONS ACROSS WHICH QLCS HAS PASSED
HAVE BEEN SUB-SVR...PEAKING AT 44 KT AT RDG AT 2059Z.  GIVEN
PRESENCE OF WEAK DEEP-LAYER SHEAR...ACTIVITY IS DRIVEN LARGELY BY
FORCED ASCENT ALONG ITS GUST FRONT...WHICH HAS SURGED AHEAD OF MAIN
REFLECTIVELY CORES IN SOME AREAS.  WHILE THIS COMPLEX IS NOT
EXPECTED TO UNDERGO ANY GEN STRENGTHENING...EMBEDDED BOW/LEWP
FEATURES STILL MAY POSE LOCALIZED RISK OF WIND DAMAGE EVEN WHERE
GUSTS ARE SUB-SVR.  BRIEF/LOCALIZED INTENSIFICATION ALSO MAY OCCUR
WHERE PORTIONS OF THIS LINE ENCOUNTER NJ SEA BREEZE...BEFORE
SUBSTANTIAL WEAKENING OCCURS.  NARROW RIBBON OF FAVORABLE
BOUNDARY-LAYER AIR IS EVIDENT BETWEEN DE RIVER AREA AND SEA BREEZE
FRONT OVER PORTIONS CAPE MAY/ATLANTIC/OCEAN/MONMOUTH COUNTIES NJ. 
IN THAT CORRIDOR...SFC TEMPS UPPER 80S TO LOW 90S F...AND DEW POINTS
UPPER 60S TO LOW 70S...OFFSET WEAK MID-UPPER LEVEL LAPSE RATES
ENOUGH TO YIELD MLCAPE AROUND 1500 J/KG...DECREASING NWD TOWARD
LOWER HUDSON VALLEY WHERE EARLIER CONVECTION STABILIZED AIR MASS
SOMEWHAT.  LOW-LEVEL THETAE ADVECTION MAY SUPPORT MRGL/ISOLATED SVR
POTENTIAL NE OF WW FROM NERN NJ OVER SRN NEW ENGLAND...HOWEVER
ADDITIONAL WW IS NOT ANTICIPATED ATTM GIVEN CONVECTIVE/AIR-MASS
TRENDS.

..EDWARDS.. 08/05/2012

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

ATTN...WFO...BOX...OKX...ALY...PHI...LWX...

LAT...LON   38977651 39577565 40817459 41747372 42277120 41787083
            41517104 41137149 40857244 40597339 40537392 40507407
            40437398 39837406 39387435 39207467 38937484 38927512
            38717509 38717586 38977651

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 5, 3:41 PM EDT	Mesoscale Discussion	SPC		94 min
Aug 5, 2:49 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle	86 min
Aug 5, 3:36 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle	5 hr
Aug 5, 12:06 PM EDT	Mesoscale Discussion	SPC	Allegany, Cattaraugus, Cayuga, Chautauqua, Erie, Genesee and 10 more	84 min
Aug 5, 12:42 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Cattaraugus, Cayuga, Chautauqua, Chemung, Cortland and 20 more	6 hr
Aug 5, 4:21 PM EDT	Mesoscale Discussion	SPC	Cayuga, Clinton, Cortland, Essex, Franklin, Fulton and 13 more	84 min
Aug 4, 10:46 PM EDT	Mesoscale Discussion	SPC	Mercer	119 min

Nearby

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