Alert archive / Massachusetts / Mesoscale Discussions in 2011
Mesoscale Discussion 2221
The Storm Prediction Center issued this mesoscale discussion at Oct 1, 2011, 5:38 AM EDT for Barnstable County, Dukes County, Nantucket County, Massachusetts. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 1, 2011, 5:38 AM EDT (09:38 UTC)
- Expired
- Oct 1, 2011, 7:45 AM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
Counties Barnstable County, MA, Dukes County, MA, Nantucket County, MA
The radar
The Boston radar (KBOX), 75 km from the middle of the area, began a volume at 09:37 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
Chatham, MA (KCHH), launched 00:00Z, 9.6 hours before the alert went out and 58 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.
- Mixed-layer CAPE
- 177 J/kg
- Mixed-layer CIN
- -13 J/kg
- Mixed-layer LCL
- 751 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 103 m²/s²
- 0-3 km storm-relative helicity
- 106 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted, in the capitals the NWS used until 2016.
901
ACUS11 KWNS 010938
SWOMCD
SPC MCD 010938
MAZ000-011145-
MESOSCALE DISCUSSION 2221
NWS STORM PREDICTION CENTER NORMAN OK
0438 AM CDT SAT OCT 01 2011
AREAS AFFECTED...SERN MA INCLUDING THE ISLANDS AND CAPE COD
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 010938Z - 011145Z
AN ISOLATED THREAT EXISTS FOR WATERSPOUTS AND/OR A TORNADO...AND A
STRONG WIND GUST TO AFFECT SERN MA...GENERALLY S AND E FROM AND
INCLUSIVE OF BRISTOL TO PLYMOUTH COUNTIES. THIS ONGOING THREAT WILL
CONTINUE THROUGH AT LEAST 12Z.
EARLY MORNING SURFACE ANALYSIS SHOWED AN AREA OF LOW PRESSURE
CENTERED S OF ERN LONG ISLAND WITH A BOUNDARY EXTENDING ENEWD TO
JUST W OF DUKES COUNTY AND THEN ACROSS FAR SERN MA BEFORE EXTENDING
OFFSHORE TO E OF PLYMOUTH COUNTY IN THE NRN EXTENT OF CAPE COD BAY
/35 SE OF BOS/. THIS BOUNDARY THEN EXTENDED NWD JUST E OF THE ERN
MA COAST AND NEWD ALONG AND JUST OFFSHORE THE ME COAST. GIVEN SELY
SURFACE WINDS ALONG CAPE COD AND OFFSHORE TO THE ISLANDS /DUKES AND
NANTUCKET COUNTIES/...THE APPARENT WARM SECTOR INCLUDES THESE AREAS.
DESPITE WEAK MIDLEVEL LAPSE RATES...A WARM/MOIST BOUNDARY LAYER
ACROSS THE WARM SECTOR IS RESULTING IN MODERATE INSTABILITY.
WATER VAPOR IMAGERY SHOWED A DEEP CLOSED LOW DIGGING SEWD FROM THE
UPPER OH VALLEY...WHILE A LEADING SHORTWAVE TROUGH LIFTS NEWD FROM
THE MID ATLANTIC COAST TOWARD SRN NEW ENGLAND EARLY THIS MORNING.
FORCING FOR ASCENT ATTENDANT TO THE LEAD TROUGH COMBINED WITH MUCAPE
OF 1000-2000 J/KG INTO SERN MA AND INCREASING EFFECTIVE BULK SHEAR
AS A 50-60 KT JET ROUNDS THE BASE OF THE ERN U.S. TROUGH WILL
SUPPORT ADDITIONAL TSTMS INVOF AND NE OF THE OFFSHORE SURFACE LOW.
THE WEAKNESS IN MIDLEVEL LAPSE RATES AND SOME SURFACE BASED
INHIBITION PER OBJECTIVE ANALYSES SUGGEST THE OVERALL COVERAGE FOR
SUSTAINED ORGANIZED TSTMS WILL REMAIN LOW. DESPITE THIS LIMITING
FACTOR IN TSTM COVERAGE...THE AVAILABLE KINEMATICS WITH ENHANCED LOW
LEVEL SHEAR NEAR THE OFFSHORE LOW AND SURFACE BOUNDARY WILL CONTINUE
TO SUPPORT A POTENTIAL FOR WATERSPOUTS AND/OR A TORNADO.
..PETERS.. 10/01/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BOX...
LAT...LON 40897148 41537091 41947054 42217017 41786983 41236987
40967038 40897148Nearby
Mesoscale Discussions in Massachusetts, 2011Every 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.