Alert archive / Iowa / Mesoscale Discussions in 2004

Mesoscale Discussion 1639

July 12, 20047 counties in Iowa; Jackson County, Nobles County, Rock County, Minnesota; 7 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 12, 2004, 11:52 PM CDT for 7 counties in Iowa; Jackson County, Nobles County, Rock County, Minnesota; 7 counties in South Dakota. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued
Jul 12, 2004, 11:52 PM CDT (04:52 UTC)
Expired
Jul 13, 2004, 12:45 AM CDT
In force
53 min
Issued by
the Storm Prediction Center

Counties Cherokee County, IA, Dickinson County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Jackson County, MN, Nobles County, MN, Rock County, MN, Clay County, SD, Lincoln County, SD, McCook County, SD, Minnehaha County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 50 km from the middle of the area, began a volume at 04:52 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

Omaha, NE (KOAX), launched 00:00Z, 4.9 hours before the alert went out and 209 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, Omaha, NE at 00:00Z on 2004-07-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4686 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, Omaha, NE at 00:00Z on 2004-07-13The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 101 square meters per square second.193958Sfc1 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
4686 J/kg
Mixed-layer CIN
-62 J/kg
Mixed-layer LCL
1125 m above ground
0-6 km bulk shear
27 kt
0-1 km storm-relative helicity
101 m²/s²
0-3 km storm-relative helicity
194 m²/s²
Significant tornado parameter
3.2
Supercell composite
20.9

Open this sounding in Storm Lab

The text

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

984 
ACUS11 KWNS 130452
SWOMCD
SPC MCD 130452 
MNZ000-IAZ000-NEZ000-SDZ000-130545-

MESOSCALE DISCUSSION 1639
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CDT MON JUL 12 2004

AREAS AFFECTED...SE SD...NW IA

CONCERNING...TORNADO WATCH 613...

VALID 130452Z - 130545Z

NEW SEVERE WW MAY BE NEEDED BY CURRENT 06Z EXPIRATION.

WEAK NEW SURFACE LOW HAS DEVELOPED IN SURFACE TROUGH TO THE WEST OF
SIOUX FALLS.  THIS IS IN ASSOCIATION WITH SHORT WAVE TROUGH DIGGING
FROM THE NORTH CENTRAL CANADIAN/U.S. BORDER AREA TOWARD THE UPPER
MISSISSIPPI VALLEY.  FAVORABLE LARGE-SCALE FORCING NEAR/EAST OF LOW
HAS BECOME FOCUS FOR INCREASING CONVECTIVE DEVELOPMENT PAST COUPLE
OF HOURS...AND SHOULD SLOWLY DEVELOP SOUTHEASTWARD WITH LOW
OVERNIGHT.  CONVECTION WILL BE SLOW TO PROGRESS OUT OF SOUTHEASTERN
SOUTH DAKOTA/NORTHWEST IOWA...IN ENVIRONMENT WITH LARGE CAPE FOR
PARCELS LIFTED ABOVE NEAR SURFACE INVERSION LAYER.

..KERR.. 07/13/2004

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

ATTN...WFO...FSD...OAX...

43799730 44049614 43809532 43549496 42679560 42519591
42419618 42529667 42759747 43359773

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 12, 9:15 PM CDTSevere Thunderstorm WatchSPCAdair, Adams, Audubon, Boone, Buena Vista, Calhoun and 32 more7 hr
Jul 12, 9:19 PM CDTMesoscale DiscussionSPCClay, Dickinson, Emmet, Hancock, Kossuth, Lyon and 5 more116 min
Jul 12, 11:19 PM CDTMesoscale DiscussionSPCAdair, Adams, Cass, Decatur, Fremont, Mills and 6 more116 min
Jul 13, 12:55 AM CDTSevere Thunderstorm WatchSPCAdair, Audubon, Benton, Black Hawk, Boone, Bremer and 52 more6 hr
Jul 13, 4:21 AM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 22 more54 min
Jul 13, 10:32 AM CDTMesoscale DiscussionSPCCedar, Clinton, Delaware, Dubuque, Jackson, Johnson and 4 more118 min
Jul 13, 10:55 AM CDTTornado WatchSPCCedar, Clinton, Delaware, Dubuque, Jackson, Jones and 3 more6 hr
Jul 13, 1:39 PM CDTMesoscale DiscussionSPCCedar, Clinton, Delaware, Dubuque, Jackson, Jones and 3 more66 min
Jul 13, 2:25 PM CDTSevere Thunderstorm WatchSPCFremont, Harrison, Mills, Monona, Pottawattamie, Shelby6 hr
Jul 12, 9:50 PM CDTSevere Thunderstorm WatchSPCBecker, Big Stone, Blue Earth, Brown, Chippewa, Clay and 38 more6 hr
Jul 13, 1:20 AM CDTSevere Thunderstorm WatchSPCAitkin, Benton, Carlton, Cass, Chisago, Crow Wing and 6 more6 hr
Jul 13, 3:35 AM CDTMesoscale DiscussionSPCAnoka, Benton, Carver, Chippewa, Chisago, Hennepin and 20 more55 min

Nearby

Mesoscale Discussions in Iowa, 2004Mesoscale Discussions in South Dakota, 2004Mesoscale Discussions in Minnesota, 2004Every mesoscale discussion in 2004

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.