Alert archive / New York / Mesoscale Discussions in 2013

Mesoscale Discussion 751

May 21, 20134 counties in Massachusetts; 23 counties in New York

The Storm Prediction Center issued this mesoscale discussion at May 21, 2013, 12:54 PM EDT for 4 counties in Massachusetts; 23 counties in New York. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: May 21, 2013, 12:54 PM EDT (16:54 UTC)
Expired: May 21, 2013, 2:00 PM EDT
In force: 66 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 27 counties

Berkshire County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Albany County, NY, Broome County, NY, Cayuga County, NY, Chenango County, NY, Columbia County, NY, Cortland County, NY, Delaware County, NY, Greene County, NY, Livingston County, NY, Madison County, NY, Montgomery County, NY, Onondaga County, NY, Ontario County, NY, Otsego County, NY, Rensselaer County, NY, Schenectady County, NY, Schoharie County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Yates County, NY

The radar

The Albany radar (KENX), 64 km from the middle of the area, began a volume at 16:55 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.

The nearest sounding before it

Albany, NY (KALY), launched 12:00Z, 4.9 hours before the alert went out and 84 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: 98 J/kg
Mixed-layer CIN: -172 J/kg
Mixed-layer LCL: 819 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 119 m²/s²
0-3 km storm-relative helicity: 149 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.3

Open this sounding in Storm Lab

The text

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

874 
ACUS11 KWNS 211655
SWOMCD
SPC MCD 211654 
NHZ000-MAZ000-CTZ000-VTZ000-NYZ000-211800-

MESOSCALE DISCUSSION 0751
NWS STORM PREDICTION CENTER NORMAN OK
1154 AM CDT TUE MAY 21 2013

AREAS AFFECTED...WRN/CNTRL NY...SRN NEW ENGLAND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 211654Z - 211800Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS SHOULD CONTINUE INCREASING IN INTENSITY...PRIMARILY
FOCUSED ALONG/S OF A QUASI-STATIONARY FRONT...ACROSS PORTIONS OF
WRN/CNTRL NY AND INTO SRN NEW ENGLAND THIS AFTERNOON. THE PRIMARY
THREATS WILL BE DMGG WIND GUSTS AND LARGE HAIL. A WW MAY BE NEEDED
IF CONVECTIVE TRENDS CONTINUE TO INCREASE.

DISCUSSION...SUBJECTIVE SFC ANALYSIS FROM 16Z PLACES A
QUASI-STATIONARY FRONT FROM NEAR ROC-ALB. A FEW STORMS HAVE RECENTLY
INITIATED ALONG THIS FRONT...LIKELY IN RESPONSE TO WEAK LOW-LEVEL
CONVERGENCE...WEAKENING CONVECTIVE INHIBITION...AND MODEST MIDLEVEL
MOISTENING/ASCENT AS NOTED ON WATER VAPOR. MODIFIED 12Z SOUNDINGS
FROM BOTH BUF AND ALB SUGGEST AMPLE INSTABILITY FOR THE DEVELOPMENT
OF STRONG-SVR TSTMS...WITH MLCAPE VALUES LIKELY EXCEEDING 2000
J/KG...GIVEN THE PRESENCE OF MODERATELY STEEP MIDLEVEL LAPSE RATES
AND RICH LOW-LEVEL MOISTURE. ADDITIONALLY...BOTH SOUNDING AND RECENT
VWP DATA SHOW NEARLY 30 KTS OF MIDLEVEL FLOW AND MODESTLY VEERING
WINDS WITH HEIGHT...SUPPORTIVE FOR ORGANIZED TSTM. COVERAGE OF TSTMS
IS SOMEWHAT UNCERTAIN GIVEN RELATIVELY WEAK FORCING FOR ASCENT...BUT
WITH THE POTENTIAL FOR LARGE HAIL AND DMGG WIND GUSTS...A WW MAY BE
REQUIRED SHOULD TRENDS CONTINUE TO INCREASE.

..ROGERS/KERR.. 05/21/2013

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

ATTN...WFO...BOX...ALY...BGM...BUF...

LAT...LON   41997433 42067611 42277755 42697790 43147756 43197706
            43027555 42987423 42957307 42897266 42677229 42257234
            41717280 41997433

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 21, 1:40 PM EDT	Severe Thunderstorm Watch	SPC	Northwest Hills Planning Region	10 hr
May 21, 2:03 PM EDT	Severe Thunderstorm Watch	SPC	Capitol Planning Region, Northeastern Connecticut Planning Region	7 hr
May 21, 4:37 PM EDT	Mesoscale Discussion	SPC		53 min
May 21, 6:09 PM EDT	Mesoscale Discussion	SPC		66 min

Nearby

Mesoscale Discussions in New York, 2013 Mesoscale Discussions in Massachusetts, 2013 Mesoscale Discussions in Connecticut, 2013 Every mesoscale discussion in 2013

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.