Alert archive / Maine / Mesoscale Discussions in 2007

Mesoscale Discussion 1921

August 30, 20076 counties in Maine; Coos County, Grafton County, New Hampshire; 4 counties in Vermont

The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2007, 11:07 AM EDT for 6 counties in Maine; Coos County, Grafton County, New Hampshire; 4 counties in Vermont. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Aug 30, 2007, 11:07 AM EDT (15:07 UTC)
Expired: Aug 30, 2007, 1:00 PM EDT
In force: 113 min
Issued by: the Storm Prediction Center

Counties Franklin County, ME, Kennebec County, ME, Oxford County, ME, Penobscot County, ME, Piscataquis County, ME, Somerset County, ME, Coos County, NH, Grafton County, NH, Caledonia County, VT, Essex County, VT, Orange County, VT, Washington County, VT

The radar

The Portland,ME radar (KGYX), 110 km from the middle of the area, began a volume at 15:10 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

Gray, ME (KGYX), launched 12:00Z, 3.1 hours before the alert went out and 110 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: 106 J/kg
Mixed-layer CIN: -343 J/kg
Mixed-layer LCL: 1254 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 36 m²/s²
0-3 km storm-relative helicity: 54 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.

000 
ACUS11 KWNS 301508
SWOMCD
SPC MCD 301507 
MEZ000-NHZ000-VTZ000-301700-

MESOSCALE DISCUSSION 1921
NWS STORM PREDICTION CENTER NORMAN OK
1007 AM CDT THU AUG 30 2007

AREAS AFFECTED...VT NH ME

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 301507Z - 301700Z

CHANCES FOR STRONG TO ISOLATED SEVERE STORMS SHOULD INCREASE THROUGH
THE AFTERNOON ACROSS PARTS OF NRN NEW ENGLAND. THIS POTENTIAL MAY
ALSO DEVELOP SWWD INTO PARTS OF ERN NY...SRN VT/NH...AND MA LATER
TODAY. AN UPGRADE TO SLGT RISK ACROSS PARTS OF THESE AREAS IS
POSSIBLE IN THE NEXT SWODY1 AND A WATCH IS ALSO POSSIBLE IF STORMS
INCREASE IN COVERAGE AND INTENSITY OVER THE NEXT FEW HOURS.

ASCENT ACROSS DEEP-LAYER FONTAL ZONE...NOW EXTENDING FROM NERN NY TO
NRN ME...WAS LIKELY BEING ENHANCED BENEATH RIGHT ENTRANCE REGION OF
UPPER LEVEL JET MAX SITUATED ACROSS ERN CANADA. MORE FOCUSED FORCING
ALONG THE BOUNDARY APPEARS TO BE SUPPORTING STRONG TSTM NOW TRACKING
EWD OVER THE UPPER CT RIVER VALLEY/NRN NH AT ABOUT 40KT.
WELL-DEFINED DIFFERENTIAL HEATING ZONE AHEAD OF THIS PARTICULAR
CELL...FROM NRN NH INTO WRN ME...AND FORCING/SHEAR ALONG THIS
CORRIDOR...COULD ENHANCE STORM SCALE PROCESSES OVER THE NEXT HOUR OR
SO WITH GUSTY WINDS POSSIBLE.

GIVEN CLEAR SKIES AHEAD OF THE FRONT...STRONG HEATING AND MODEST
MOISTURE WILL CONTRIBUTE TO CONTINUED DESTABILIZATION INTO THE
AFTERNOON. WITH SOMEWHAT MARGINAL MID LEVEL LAPSE RATES IN THE RANGE
OF 6-7 C/KM...MLCAPE VALUES WILL PROBABLY MAX OUT AROUND 1000 J/KG
FOR SURFACE TEMPERATURES IN THE LOWER 80S F. AS INHIBITION IS
OVERCOME AND FRONT SETTLES SEWD...ADDITIONAL TSTM DEVELOPMENT SHOULD
ENSUE. AS USUAL...STRONGER DEEP-LAYER SHEAR WILL REMAIN CONFINED TO
THE COOL SIDE OF THE BOUNDARY. HOWEVER...SHEAR ALONG THE IMMEDIATE
FRONTAL ZONE...AND WELL-MIXED BOUNDARY LAYER AHEAD OF THE
FRONT...COULD SUPPORT WIDELY SCATTERED WIND DAMAGE FROM A COUPLE OF
THE MORE ROBUST TSTMS. GIVEN THIS SCENARIO...A SLGT RISK WILL LIKELY
BE ADDED TO THE NEXT SWODY1 ACROSS PARTS OF THE REGION. A WATCH IS
ALSO POSSIBLE IF IT APPEARS STRONG TO SEVERE STORM ACTIVITY IS
BECOMING MORE WIDESPREAD THROUGH THE AFTERNOON.

..CARBIN.. 08/30/2007

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

ATTN...WFO...CAR...GYX...BTV...

45357084 45856929 46386796 45836788 45216810 44346989
44017098 43827162 43727242 44007300 44587264

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 2:20 PM EDT	Mesoscale Discussion	SPC	Oxford	115 min
Aug 30, 3:07 PM EDT	Severe Thunderstorm Watch	SPC	Androscoggin, Cumberland, Franklin, Kennebec, Knox, Lincoln and 5 more	6 hr
Aug 30, 5:00 PM EDT	Mesoscale Discussion	SPC	Androscoggin, Cumberland, Franklin, Kennebec, Lincoln, Oxford and 3 more	60 min
Aug 30, 6:23 PM EDT	Mesoscale Discussion	SPC	Androscoggin, Cumberland, Franklin, Kennebec, Oxford, Penobscot and 4 more	97 min

Nearby

Mesoscale Discussions in Maine, 2007 Mesoscale Discussions in Vermont, 2007 Mesoscale Discussions in New Hampshire, 2007 Every mesoscale discussion in 2007

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.