Alert archive / Michigan / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 849

September 12, 201113 counties in Michigan; 9 counties in Wisconsin

The Storm Prediction Center issued this severe thunderstorm watch at Sep 12, 2011, 8:09 PM EDT for 13 counties in Michigan; 9 counties in Wisconsin. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Sep 12, 2011, 8:09 PM EDT (00:09 UTC)
Expired: Sep 12, 2011, 11:47 PM EDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 60 kt

All 22 counties

Alger County, MI, Baraga County, MI, Delta County, MI, Dickinson County, MI, Gogebic County, MI, Houghton County, MI, Iron County, MI, Keweenaw County, MI, Luce County, MI, Marquette County, MI, Menominee County, MI, Ontonagon County, MI, Schoolcraft County, MI, Ashland County, WI, Florence County, WI, Forest County, WI, Iron County, WI, Marinette County, WI, Oneida County, WI, Price County, WI, Sawyer County, WI, Vilas County, WI

The radar

The Marquette radar (KMQT), 65 km from the middle of the area, began a volume at 00:12 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: 10%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 50%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 50%
One or more hailstones of 2 inches or more: 30%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Sep 12, 8:14 PM EDT	Severe Thunderstorm Warning	DLH	Ashland, Price, Sawyer	42 min
Sep 12, 8:18 PM EDT	Severe Thunderstorm Warning	MQT	Baraga, Houghton	57 min
Sep 12, 8:30 PM EDT	Severe Thunderstorm Warning	MQT	Houghton, Ontonagon	30 min
Sep 12, 9:04 PM EDT	Severe Thunderstorm Warning	MQT	Baraga, Marquette	24 min
Sep 12, 9:09 PM EDT	Severe Thunderstorm Warning	MQT	Dickinson, Iron	51 min
Sep 12, 10:00 PM EDT	Severe Thunderstorm Warning	MQT	Dickinson, Iron, Marquette, Menominee	60 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 00:00Z, 0.2 hours before the alert went out and 260 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: 893 J/kg
Mixed-layer CIN: -98 J/kg
Mixed-layer LCL: 1722 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 187 m²/s²
0-3 km storm-relative helicity: 290 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

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

597 
WWUS20 KWNS 130007
SEL9
SPC WW 130007
MIZ000-WIZ000-LMZ000-LSZ000-130500-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 849
NWS STORM PREDICTION CENTER NORMAN OK
710 PM CDT MON SEP 12 2011

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

       UPPER MICHIGAN
       EXTREME NORTHERN WISCONSIN
       LAKE MICHIGAN
       LAKE SUPERIOR

EFFECTIVE THIS MONDAY NIGHT FROM 710 PM UNTIL MIDNIGHT CDT.

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 100
STATUTE MILES EAST AND WEST OF A LINE FROM 70 MILES NORTH
NORTHEAST OF MARQUETTE MICHIGAN TO 50 MILES WEST OF IRON MOUNTAIN
MICHIGAN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).

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...VIGOROUS PV MAX WILL CONTINUE A ESE TREK ACROSS THE
GREAT LAKES THIS EVENING.  STRONG UVV WILL SUPPORT/MAINTAIN BAND OF
STG-SVR TSTMS AS THEY CROSS UPR MI AND FAR NRN WI THROUGH LATE THIS
EVENING.  STRONG FORCING FOR ASCENT AND STRONG WIND FIELDS THROUGH
THE COLUMN WILL SUPPORT A FEW BOW ECHOES/EMBEDDED SUPERCELLS WITH
LARGE HAIL AND DMGG WIND GUSTS.

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 27030.


...RACY

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 12, 11:06 PM EDT	Mesoscale Discussion	SPC	Alger, Baraga, Delta, Dickinson, Iron, Luce and 4 more	54 min

Nearby

Severe Thunderstorm Watches in Michigan, 2011 Severe Thunderstorm Watches in Wisconsin, 2011 Every severe thunderstorm watch 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.