Alert archive / Massachusetts / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 511

July 24, 20124 states

The Storm Prediction Center issued this severe thunderstorm watch at Jul 24, 2012, 1:38 PM EDT for 4 states. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jul 24, 2012, 1:38 PM EDT (17:38 UTC)
Expired: Jul 24, 2012, 7:12 PM EDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 60 kt

All 22 counties

Capitol Planning Region, CT, Northeastern Connecticut Planning Region, CT, Barnstable County, MA, Bristol County, MA, Dukes County, MA, Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Nantucket County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Cheshire County, NH, Hillsborough County, NH, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI

The radar

The Boston radar (KBOX), 64 km from the middle of the area, began a volume at 17:38 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 20%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Jul 24, 1:41 PM EDT	Severe Thunderstorm Warning	BOX	Hillsborough	28 min
Jul 24, 3:07 PM EDT	Severe Thunderstorm Warning	BOX	Hampden, Hampshire, Middlesex, Norfolk, Worcester	36 min
Jul 24, 4:23 PM EDT	Severe Thunderstorm Warning	BOX	Barnstable, Plymouth	30 min
Jul 24, 5:00 PM EDT	Severe Thunderstorm Warning	BOX	Bristol, Plymouth	30 min
Jul 24, 5:41 PM EDT	Severe Thunderstorm Warning	BOX	Barnstable, Dukes	37 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

Mesoscale Discussion 1567Jul 24, 12:52 PM EDT

The nearest sounding before it

Chatham, MA (KCHH), launched 12:00Z, 5.6 hours before the alert went out and 161 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: 313 J/kg
Mixed-layer CIN: -144 J/kg
Mixed-layer LCL: 967 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 94 m²/s²
0-3 km storm-relative helicity: 142 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.

684 
WWUS20 KWNS 241736
SEL1
SPC WW 241736
CTZ000-MAZ000-NHZ000-RIZ000-CWZ000-250000-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 511
NWS STORM PREDICTION CENTER NORMAN OK
140 PM EDT TUE JUL 24 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       NORTHERN CONNECTICUT
       CENTRAL AND EASTERN MASSACHUSETTS
       SOUTHERN NEW HAMPSHIRE
       RHODE ISLAND
       COASTAL WATERS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 140 PM UNTIL
800 PM EDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 45
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES NORTH
NORTHWEST OF WESTFIELD MASSACHUSETTS TO 30 MILES NORTHEAST OF
HYANNIS MASSACHUSETTS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 508...WW 509...WW 510...

DISCUSSION...SCATTERED THUNDERSTORMS ARE SLOWLY INTENSIFYING ALONG A
COLD FRONT EXTENDING FROM THE COAST OF ME INTO EASTERN NY.  COOL
TEMPERATURES ALOFT AND STEEP LOW/MID LEVEL LAPSE RATES WILL PROMOTE
A RISK OF A FEW SEVERE STORMS CAPABLE OF DAMAGING WINDS AND HAIL
THIS AFTERNOON.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 28025.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 23, 10:29 PM EDT	Mesoscale Discussion	SPC	Berkshire	91 min
Jul 24, 12:52 PM EDT	Mesoscale Discussion	SPC	Barnstable, Bristol, Dukes, Essex, Middlesex, Norfolk and 3 more	83 min
Jul 24, 2:29 AM EDT	Mesoscale Discussion	SPC	Belknap, Carroll, Coos, Grafton, Strafford	31 min

Nearby

Severe Thunderstorm Watches in Massachusetts, 2012 Severe Thunderstorm Watches in Rhode Island, 2012 Severe Thunderstorm Watches in Connecticut, 2012 Every severe thunderstorm watch 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.