Alert archive / Iowa / Mesoscale Discussions in 2011

Mesoscale Discussion 749

May 11, 20114 states

The Storm Prediction Center issued this mesoscale discussion at May 11, 2011, 8:16 PM CDT for 4 states. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued: May 11, 2011, 8:16 PM CDT (01:16 UTC)
Expired: May 11, 2011, 9:15 PM CDT
In force: 59 min
Issued by: the Storm Prediction Center

Counties Adams County, IA, Fremont County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Taylor County, IA, Brown County, KS, Nemaha County, KS, Atchison County, MO, Holt County, MO, Nodaway County, MO, Cass County, NE, Johnson County, NE, Nemaha County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE

The radar

The Omaha radar (KOAX), 128 km from the middle of the area, began a volume at 01:19 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

Omaha, NE (KOAX), launched 00:00Z, 1.3 hours before the alert went out and 128 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: 18 J/kg
Mixed-layer CIN: -235 J/kg
Mixed-layer LCL: 1238 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 307 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

550 
ACUS11 KWNS 120116
SWOMCD
SPC MCD 120116 
IAZ000-MOZ000-KSZ000-NEZ000-120215-

MESOSCALE DISCUSSION 0749
NWS STORM PREDICTION CENTER NORMAN OK
0816 PM CDT WED MAY 11 2011

AREAS AFFECTED...FAR NORTHEAST KS/SOUTHEAST NEB/NORTHWEST
MO/SOUTHWEST IA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 120116Z - 120215Z

SEVERE TSTM WATCH 284 CONTINUES UNTIL 03Z ACROSS FAR EASTERN KS AND
MO. AT LEAST ON AN ISOLATED BASIS...SEVERE TSTMS CAPABLE OF
HAIL/DAMAGING WINDS WILL CONTINUE THIS EVENING ACROSS FAR NORTHEAST
KS/SOUTHEAST NEB INTO FAR NORTHWEST MO/SOUTHWEST IA. AN ADDITIONAL
WATCH IS NOT CURRENTLY EXPECTED TO THE NORTH/WEST OF WW 284...BUT
TRENDS WILL CONTINUE TO BE MONITORED.

BENEATH UPPER JET EXIT REGION AND IN THE PRESENCE OF DIFFLUENT FLOW
ALOFT...STRONG/SEVERE TSTMS HAVE RECENTLY DEVELOPED IN VICINITY OF
EFFECTIVE SURFACE BOUNDARY/PRIOR OUTFLOW NEAR THE NORTHEAST
KS/SOUTHEAST NEB BORDER. A MODERATELY UNSTABLE AIRMASS IS IN PLACE
ALONG/SOUTH OF THIS BOUNDARY...WITH THE 00Z TOPEKA OBSERVED RAOB
INDICATIVE OF 7.4 C/KM MID LEVEL LAPSE RATES AND 1800 J/KG OF
MLCAPE. HOWEVER...VERTICAL SHEAR COINCIDENT WITH THE
BOUNDARY/ADJACENT WARM SECTOR IS RELATIVELY WEAK PER REGIONAL
WSR-88D VWPS...SUCH THAT THE CONVECTIVE MODE/SEVERE THREAT SHOULD
REMAIN MULTICELLULAR/EPISODIC IN NATURE. WHILE THE SEVERE THREAT IS
NOT EXPECTED TO BE PARTICULARLY ORGANIZED...BOUTS OF SEVERE HAIL
WILL NONETHELESS REMAIN POSSIBLE. FURTHERMORE...AMPLE
INSTABILITY/LAPSE RATES ALOFT AND PRECIPITATION LOADING IMPLY
POTENTIAL FOR LOCALIZED STRONG DOWNDRAFTS AS WELL...WITH A 45 KT
MEASURED GUST RECENTLY NOTED AT FALLS CITY IN EXTREME SOUTHEAST NEB.

..GUYER.. 05/12/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DMX...EAX...OAX...TOP...

LAT...LON   40159509 39649541 39749618 40589648 41199588 41299458
            40799440 40159509

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 12, 2:37 PM CDT	Tornado Watch	SPC	Harrison, Monona, Shelby	7 hr
May 12, 5:35 PM CDT	Mesoscale Discussion	SPC	Calhoun, Carroll, Crawford, Harrison, Ida, Monona and 4 more	85 min
May 12, 6:05 PM CDT	Severe Thunderstorm Watch	SPC	Adair, Adams, Audubon, Black Hawk, Boone, Bremer and 32 more	7 hr
May 11, 7:51 PM CDT	Mesoscale Discussion	SPC	Cheyenne, Decatur, Norton, Rawlins, Sherman, Thomas	84 min
May 12, 3:17 PM CDT	Severe Thunderstorm Watch	SPC	Bourbon, Cherokee, Crawford	7 hr
May 12, 4:54 PM CDT	Mesoscale Discussion	SPC	Atchison, Douglas, Jefferson, Johnson, Leavenworth, Linn and 2 more	66 min
May 12, 5:31 PM CDT	Severe Thunderstorm Watch	SPC	Linn, Miami	6 hr
May 12, 6:30 PM CDT	Mesoscale Discussion	SPC	Cherokee	90 min
May 12, 1:46 PM CDT	Mesoscale Discussion	SPC	McDonald, Newton	119 min
May 12, 2:06 PM CDT	Mesoscale Discussion	SPC	Adams, Boone, Buffalo, Butler, Cass, Clay and 39 more	114 min

Nearby

Mesoscale Discussions in Iowa, 2011 Mesoscale Discussions in Nebraska, 2011 Mesoscale Discussions in Missouri, 2011 Every mesoscale discussion 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.