Alert archive / Illinois / Mesoscale Discussions in 2013

Mesoscale Discussion 739

May 20, 201333 counties in Illinois; 16 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at May 20, 2013, 8:53 PM CDT for 33 counties in Illinois; 16 counties in Missouri. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued
May 20, 2013, 8:53 PM CDT (01:53 UTC)
Expired
May 20, 2013, 10:00 PM CDT
In force
67 min
Issued by
the Storm Prediction Center
All 49 counties

Adams County, IL, Bond County, IL, Brown County, IL, Calhoun County, IL, Cass County, IL, Christian County, IL, Clinton County, IL, DeWitt County, IL, Fayette County, IL, Fulton County, IL, Greene County, IL, Hancock County, IL, Jersey County, IL, Knox County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Peoria County, IL, Pike County, IL, Saint Clair County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Tazewell County, IL, Woodford County, IL, Audrain County, MO, City of Saint Louis, MO, Franklin County, MO, Gasconade County, MO, Jefferson County, MO, Lewis County, MO, Lincoln County, MO, Marion County, MO, Monroe County, MO, Montgomery County, MO, Pike County, MO, Ralls County, MO, Saint Charles County, MO, Saint Louis County, MO, Shelby County, MO, Warren County, MO

The radar

The Lincoln radar (KILX), 101 km from the middle of the area, began a volume at 01:54 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 1.9 hours before the alert went out and 159 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, Lincoln, IL at 00:00Z on 2013-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1540 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, Lincoln, IL at 00:00Z on 2013-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 31 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
1540 J/kg
Mixed-layer CIN
-5 J/kg
Mixed-layer LCL
1320 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
31 m²/s²
0-3 km storm-relative helicity
173 m²/s²
Significant tornado parameter
0.8
Supercell composite
6.7

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.

IssuedProductOfficeCountiesLasted
May 20, 7:17 PM CDTMesoscale DiscussionSPCBoone, Bureau, Carroll, DeKalb, DeWitt, DuPage and 25 more58 min
May 20, 7:39 PM CDTTornado WatchSPCRandolph6 hr
May 20, 7:48 PM CDTSevere Thunderstorm WatchSPCBoone, Bureau, Carroll, Cook, DeKalb, DuPage and 20 more6 hr
May 20, 8:07 PM CDTMesoscale DiscussionSPCCalhoun, Pike23 min
May 20, 10:25 PM CDTMesoscale DiscussionSPCAlexander, Champaign, Clark, Clay, Coles, Crawford and 33 more65 min
May 20, 10:56 PM CDTTornado WatchSPCAlexander, Champaign, Clark, Clay, Coles, Crawford and 29 more6 hr
May 21, 2:59 AM CDTMesoscale DiscussionSPCAlexander, Franklin, Gallatin, Hamilton, Hardin, Johnson and 7 more91 min
May 21, 12:50 AM CDTSevere Thunderstorm WatchSPCDunklin, Pemiscot3 hr
May 21, 7:47 AM CDTMesoscale DiscussionSPCDunklin, Pemiscot58 min
May 21, 2:42 PM CDTMesoscale DiscussionSPCDunklin, Pemiscot63 min
May 21, 3:00 PM CDTTornado WatchSPCDunklin, Pemiscot7 hr

Nearby

Mesoscale Discussions in Illinois, 2013Mesoscale Discussions in Missouri, 2013Every mesoscale discussion in 2013

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.