Alert archive / Iowa / Mesoscale Discussions in 2015

Mesoscale Discussion 1812

September 17, 20156 counties in Iowa; 4 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Sep 17, 2015, 7:54 PM CDT for 6 counties in Iowa; 4 counties in Missouri. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Sep 17, 2015, 7:54 PM CDT (00:54 UTC)
Expired: Sep 17, 2015, 9:00 PM CDT
In force: 66 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Des Moines County, IA, Henry County, IA, Jefferson County, IA, Lee County, IA, Louisa County, IA, Van Buren County, IA, Clark County, MO, Knox County, MO, Lewis County, MO, Scotland County, MO

The radar

The Quad Cities radar (KDVN), 153 km from the middle of the area, began a volume at 00:57 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

Davenport, (KDVN), launched 00:00Z, 0.9 hours before the alert went out and 158 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: 1343 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 1492 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 211 m²/s²
0-3 km storm-relative helicity: 495 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 15.7

Open this sounding in Storm Lab

The text

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

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 17, 10:12 PM CDT	Mesoscale Discussion	SPC	Appanoose, Clarke, Decatur, Lucas, Monroe, Ringgold and 1 more	63 min
Sep 18, 9:25 AM CDT	Mesoscale Discussion	SPC	Adams, Cass, Fremont, Mills, Montgomery, Page and 4 more	65 min
Sep 18, 5:20 PM CDT	Mesoscale Discussion	SPC	Davis, Des Moines, Henry, Lee, Van Buren	2 hr

Nearby

Mesoscale Discussions in Iowa, 2015 Mesoscale Discussions in Missouri, 2015 Every mesoscale discussion in 2015

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.