Alert archive / Michigan / Mesoscale Discussions in 2012

Mesoscale Discussion 1950

September 17, 201211 counties in Illinois; 19 counties in Michigan; 6 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Sep 17, 2012, 1:30 PM CDT for 11 counties in Illinois; 19 counties in Michigan; 6 counties in Wisconsin. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: Sep 17, 2012, 1:30 PM CDT (18:30 UTC)
Expired: Sep 17, 2012, 2:30 PM CDT
In force: 60 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 36 counties

Boone County, IL, Carroll County, IL, DeKalb County, IL, Kane County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Alpena County, MI, Clare County, MI, Crawford County, MI, Kalkaska County, MI, Lake County, MI, Mecosta County, MI, Missaukee County, MI, Montmorency County, MI, Muskegon County, MI, Newaygo County, MI, Oceana County, MI, Ogemaw County, MI, Osceola County, MI, Oscoda County, MI, Otsego County, MI, Ottawa County, MI, Presque Isle County, MI, Roscommon County, MI, Wexford County, MI, Kenosha County, WI, Milwaukee County, WI, Racine County, WI, Rock County, WI, Walworth County, WI, Waukesha County, WI

The radar

The Grand Rapids radar (KGRR), 100 km from the middle of the area, began a volume at 18:31 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.

The nearest sounding before it

Green Bay/Straub, WI (KGRB), launched 12:00Z, 6.5 hours before the alert went out and 173 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: 162 J/kg
Mixed-layer CIN: -241 J/kg
Mixed-layer LCL: 991 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 34 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

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

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Nearby

Mesoscale Discussions in Michigan, 2012 Mesoscale Discussions in Illinois, 2012 Mesoscale Discussions in Wisconsin, 2012 Every mesoscale discussion 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.