Alert archive / Maine / Mesoscale Discussions in 2011

Mesoscale Discussion 2033

August 21, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2011, 3:05 PM EDT for 4 states. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued: Aug 21, 2011, 3:05 PM EDT (19:05 UTC)
Expired: Aug 21, 2011, 4:00 PM EDT
In force: 55 min
Issued by: the Storm Prediction Center

Counties Essex County, MA, Middlesex County, MA, Norfolk County, MA, Suffolk County, MA, Worcester County, MA, Androscoggin County, ME, Cumberland County, ME, Franklin County, ME, Kennebec County, ME, Oxford County, ME, Sagadahoc County, ME, Somerset County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Rockingham County, NH, Strafford County, NH, Providence County, RI

The radar

The Portland,ME radar (KGYX), 116 km from the middle of the area, began a volume at 19:06 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 797Aug 21, 3:20 PM EDT

The nearest sounding before it

Gray, ME (KGYX), launched 12:00Z, 7.1 hours before the alert went out and 116 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: 135 J/kg
Mixed-layer CIN: -90 J/kg
Mixed-layer LCL: 1187 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 69 m²/s²
0-3 km storm-relative helicity: 18 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.

926 
ACUS11 KWNS 211905
SWOMCD
SPC MCD 211905 
MEZ000-MAZ000-NHZ000-RIZ000-CTZ000-212000-

MESOSCALE DISCUSSION 2033
NWS STORM PREDICTION CENTER NORMAN OK
0205 PM CDT SUN AUG 21 2011

AREAS AFFECTED...ERN MASSACHUSETTS...NEW HAMPSHIRE AND MAINE

CONCERNING...SEVERE THUNDERSTORM WATCH 795...

VALID 211905Z - 212000Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 795
CONTINUES.

WW 795 MAY BE LOCALLY EXTENDED IN AREA EASTWARD ACROSS PARTS OF NEW
ENGLAND.  AN ADDITIONAL WW COULD BECOME NECESSARY LATE THIS
AFTERNOON FARTHER EAST.

A VIGOROUS PRE-FRONTAL LINE OF STORMS HAS EVOLVED ACROSS WESTERN
PORTIONS OF NEW ENGLAND...WITHIN A MOIST UNSTABLE ENVIRONMENT
CHARACTERIZED BY MIXED LAYER CAPE ON THE ORDER OF 2000 J/KG.  DEEP
LAYER SOUTHWESTERLY MEAN FLOW IS STILL SOMEWHAT MODEST ON THE ORDER
OF 25-30 KT...BUT VERTICAL SHEAR...WHILE NOT STRONG...MAY BE
SUFFICIENT FOR AT LEAST SHORT-LIVED UPDRAFT ROTATION IN STRONGER
CELLS.  IT IS ALSO TENDING TO ALLOW ANVIL LEVEL CLOUD COVER AND
PRECIPITATION TO ADVECT ACROSS AND IMPACT THE DOWNSTREAM LOW-LEVEL
INFLOW LAYER...WHICH MAY ULTIMATELY LIMIT THE SEVERE THREAT ACROSS
EASTERN AND NORTHERN NEW ENGLAND.  HOWEVER...THE ENVIRONMENT ACROSS
THIS REGION HAS ALREADY RECEIVED CONSIDERABLE INSOLATION...AND
LOW-LEVEL LAPSE RATES ARE FAIRLY STEEP...SO THE RISK FOR POTENTIALLY
DAMAGING WIND GUSTS STILL CAN NOT BE RULED OUT AS STORMS SPREAD
NORTH AND EAST OF WW 795.  THIS COULD IMPACT THE GREATER BOSTON
METROPOLITAN AREA AND THE PORTLAND ME BY 21-22Z.

..KERR.. 08/21/2011

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

ATTN...WFO...CAR...GYX...BOX...OKX...

LAT...LON   42037265 42757162 44067167 45797001 44946923 43636995
            42187100 41097290 42037265

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 21, 11:54 AM EDT	Mesoscale Discussion	SPC		2 hr
Aug 21, 12:52 PM EDT	Severe Thunderstorm Watch	SPC	Greater Bridgeport Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region	8 hr
Aug 21, 1:20 PM EDT	Severe Thunderstorm Watch	SPC	Capitol Planning Region, Northwest Hills Planning Region, Northeastern Connecticut Planning Region	8 hr
Aug 21, 7:12 PM EDT	Mesoscale Discussion	SPC		63 min
Aug 21, 3:24 PM EDT	Severe Thunderstorm Watch	SPC	Androscoggin, Aroostook, Cumberland, Franklin, Kennebec, Oxford and 5 more	6 hr
Aug 21, 4:34 PM EDT	Mesoscale Discussion	SPC	Berkshire	116 min

Nearby

Mesoscale Discussions in Maine, 2011 Mesoscale Discussions in Massachusetts, 2011 Mesoscale Discussions in Connecticut, 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.