Alert archive / Massachusetts / Tornado Watches in 2012

Tornado Watch 571

August 10, 20125 counties in Connecticut; 12 counties in Massachusetts; 5 counties in Rhode Island

The Storm Prediction Center issued this tornado watch at Aug 10, 2012, 3:31 PM EDT for 5 counties in Connecticut; 12 counties in Massachusetts; 5 counties in Rhode Island. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Aug 10, 2012, 3:31 PM EDT (19:31 UTC)
Expired
Aug 10, 2012, 8:59 PM EDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
0.5 in
Strongest gust expected
60 kt
All 22 counties

Capitol Planning Region, CT, Lower Connecticut River Valley Planning Region, CT, Naugatuck Valley Planning Region, CT, Northeastern Connecticut Planning Region, CT, Southeastern Connecticut Planning Region, CT, Barnstable County, MA, Bristol County, MA, Dukes County, MA, Essex 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, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI

The radar

The Boston radar (KBOX), 27 km from the middle of the area, began a volume at 19:31 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
40%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
5%
Ten or more severe hail reports
10%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
50%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Aug 10, 3:31 PM EDTSevere Thunderstorm WarningOKXLower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region29 min
Aug 10, 3:41 PM EDTSevere Thunderstorm WarningBOXWashington19 min
Aug 10, 3:49 PM EDTSevere Thunderstorm WarningOKXLower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region41 min
Aug 10, 4:00 PM EDTSevere Thunderstorm WarningBOXCapitol Planning Region, Northeastern Connecticut Planning Region45 min
Aug 10, 4:09 PM EDTSevere Thunderstorm WarningBOXNewport, Washington36 min
Aug 10, 4:22 PM EDTTornado WarningBOXCapitol Planning Region38 min
Aug 10, 4:43 PM EDTSevere Thunderstorm WarningBOXBristol, Kent, Newport, Washington62 min
Aug 10, 4:45 PM EDTSevere Thunderstorm WarningBOXNortheastern Connecticut Planning Region45 min
Aug 10, 4:56 PM EDTFlash Flood WarningBOXCapitol Planning Region, Northeastern Connecticut Planning Region2 hr
Aug 10, 4:57 PM EDTFlash Flood WarningBOXCapitol Planning Region, Northeastern Connecticut Planning Region2 hr
Aug 10, 5:00 PM EDTTornado WarningBOXCapitol Planning Region45 min
Aug 10, 5:09 PM EDTFlash Flood WarningBOXBristol, Plymouth3 hr
Aug 10, 5:16 PM EDTSevere Thunderstorm WarningBOXBristol, Plymouth59 min
Aug 10, 5:27 PM EDTFlash Flood WarningBOXFranklin, Hampden, Hampshire, Middlesex, Norfolk, Suffolk and 1 more3 hr
Aug 10, 5:31 PM EDTSevere Thunderstorm WarningBOXNortheastern Connecticut Planning Region44 min
Aug 10, 5:33 PM EDTSevere Thunderstorm WarningBOXBristol27 min
Aug 10, 5:45 PM EDTSevere Thunderstorm WarningBOXFranklin, Hampden, Hampshire, Worcester45 min
Aug 10, 5:55 PM EDTFlash Flood WarningBOXEssex3 hr
Aug 10, 6:23 PM EDTSevere Thunderstorm WarningBOXBristol, Middlesex, Norfolk, Plymouth, Suffolk37 min

Discussions around it

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

The nearest sounding before it

Chatham, MA (KCHH), launched 12:00Z, 7.5 hours before the alert went out and 128 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-pSkew-T log-p diagram, Chatham, MA at 12:00Z on 2012-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 424 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Chatham, MA at 12:00Z on 2012-08-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 60 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
424 J/kg
Mixed-layer CIN
-29 J/kg
Mixed-layer LCL
475 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
60 m²/s²
0-3 km storm-relative helicity
77 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.

758 
WWUS20 KWNS 101933
SEL1
SPC WW 101933
CTZ000-MAZ000-RIZ000-CWZ000-110100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 571
NWS STORM PREDICTION CENTER NORMAN OK
330 PM EDT FRI AUG 10 2012

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

       CENTRAL AND EASTERN CONNECTICUT
       CENTRAL AND EASTERN MASSACHUSETTS
       RHODE ISLAND
       COASTAL WATERS

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 330 PM UNTIL 900
PM EDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHWEST OF BOSTON
MASSACHUSETTS TO 40 MILES EAST SOUTHEAST OF BLOCK ISLAND RHODE
ISLAND.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

DISCUSSION...TSTMS EXPECTED TO CONTINUE MOVING NEWD IN ASSOCIATION
WITH MID LVL VORT AND ASSOCIATED SFC WAVE NOW NEARING THE CT CST.
WHILE LOW LVL LAPSE RATES WILL REMAIN WEAK...RICH LOW LVL MOISTURE
AND FAIRLY WARM SFC TEMPS AHEAD OF THE VORT SUGGEST POTENTIAL FOR
CONTINUED DEVELOPMENT OF DISCRETE STORMS/SHOWERS ALONG AND SE OF
VORT TRACK.  RECENT OKX VWP DATA APPEAR TO CAPTURE ENHANCED WIND
FIELD ACCOMPANYING VORT...WITH LOW LVL WINDS BACKING AND
STRENGTHENING AHEAD OF IT. SETUP MAY THEREFORE YIELD A FEW
STORMS/UPDRAFTS WITH LOW LVL ROTATION AND A RISK FOR ISOLD TORNADOES
THROUGH EARLY EVE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 21030.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 10, 8:21 AM EDTMesoscale DiscussionSPC2 hr
Aug 10, 2:03 PM EDTMesoscale DiscussionSPC87 min

Nearby

Tornado Watches in Massachusetts, 2012Tornado Watches in Connecticut, 2012Tornado Watches in Rhode Island, 2012Every tornado 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.