Alert archive / Michigan / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 672

October 25, 20127 counties in Michigan

The Storm Prediction Center issued this severe thunderstorm watch at Oct 25, 2012, 9:52 AM EDT for 7 counties in Michigan. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Oct 25, 2012, 9:52 AM EDT (13:52 UTC)
Expired: Oct 25, 2012, 1:51 PM EDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

Counties Alger County, MI, Baraga County, MI, Delta County, MI, Dickinson County, MI, Iron County, MI, Marquette County, MI, Menominee County, MI

The radar

The Marquette radar (KMQT), 26 km from the middle of the area, began a volume at 13:56 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: 40%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 50%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Oct 25, 10:25 AM EDT	Severe Thunderstorm Warning	MQT	Baraga, Marquette	50 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

Green Bay/Straub, WI (KGRB), launched 12:00Z, 1.9 hours before the alert went out and 226 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: 631 J/kg
Mixed-layer CIN: -112 J/kg
Mixed-layer LCL: 681 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 100 m²/s²
0-3 km storm-relative helicity: 245 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.6

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

351 
WWUS20 KWNS 251354
SEL2
SPC WW 251354
MIZ000-LSZ000-251900-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 672
NWS STORM PREDICTION CENTER NORMAN OK
855 AM CDT THU OCT 25 2012

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

       UPPER PENINSULA OF MICHIGAN
       LAKE SUPERIOR

EFFECTIVE THIS THURSDAY MORNING AND AFTERNOON FROM 855 AM UNTIL
200 PM CDT.

HAIL TO 1 INCH 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 EITHER SIDE OF A LINE FROM 25 MILES NORTH NORTHEAST
OF MARQUETTE MICHIGAN TO 10 MILES WEST SOUTHWEST OF IRON MOUNTAIN
MICHIGAN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).

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.

DISCUSSION...BOWING SEGMENT OF CONVECTION RACING NORTHEAST AT
50-60KT HAS ALREADY PRODUCED OBSERVED GUSTS AT RHI AROUND 50KT IN
WEAK CAPE BUT INTENSE SHEAR ENVIRONMENT. EXPECT THE STORMS TO
CONTINUE NEWD TOWARD LAKE SUPERIOR OVER THE NEXT 2 HOURS WITH A
CONTINUING POTENTIAL FOR SEVERE WINDS ALONG THE PATH OF THE BOW.
GREATEST POTENTIAL WILL BE NEAR THE APEX OF THE BOWING SEGMENT WHICH
APPEARS TO BE CO-LOCATED WITH A FRONTAL WAVE RIPPLING NEWD ALONG THE
STRONG BAROCLINIC ZONE. GIVEN STEEP MID LEVEL LAPSE RATES AND ASCENT
ACROSS THE REGION...ISOLATED SEVERE HAIL AROUND 1 INCH WILL ALSO BE
POSSIBLE.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.
A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION
VECTOR 23050.


...CARBIN

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 25, 9:48 AM EDT	Mesoscale Discussion	SPC	Baraga, Dickinson, Iron	27 min
Oct 25, 12:47 PM EDT	Mesoscale Discussion	SPC	Delta, Dickinson, Menominee	58 min

Nearby

Severe Thunderstorm Watches in Michigan, 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.