Alert archive / Iowa / Mesoscale Discussions in 2008
Mesoscale Discussion 1813
The Storm Prediction Center issued this mesoscale discussion at Jul 19, 2008, 1:09 PM CDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 19, 2008, 1:09 PM CDT (18:09 UTC)
- Expired
- Jul 19, 2008, 3:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
All 60 counties
Buena Vista County, IA, Calhoun County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Hancock County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Lyon County, IA, Monona County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Wright County, IA, Blue Earth County, MN, Brown County, MN, Cottonwood County, MN, Faribault County, MN, Freeborn County, MN, Jackson County, MN, Le Sueur County, MN, Martin County, MN, Murray County, MN, Nicollet County, MN, Nobles County, MN, Redwood County, MN, Rock County, MN, Waseca County, MN, Watonwan County, MN, Antelope County, NE, Boyd County, NE, Cedar County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Holt County, NE, Knox County, NE, Pierce County, NE, Thurston County, NE, Wayne County, NE, Bon Homme County, SD, Charles Mix County, SD, Clay County, SD, Douglas County, SD, Gregory County, SD, Hutchinson County, SD, Lincoln County, SD, Minnehaha County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 72 km from the middle of the area, began a volume at 18:10 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 12:00Z, 6.2 hours before the alert went out and 223 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.
- Mixed-layer CAPE
- 708 J/kg
- Mixed-layer CIN
- -114 J/kg
- Mixed-layer LCL
- 858 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 51 m²/s²
- 0-3 km storm-relative helicity
- 115 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 3.0
The text
As transmitted, in the capitals the NWS used until 2016.
000 ACUS11 KWNS 191809 SWOMCD SPC MCD 191809 IAZ000-MNZ000-NEZ000-SDZ000-192015- MESOSCALE DISCUSSION 1813 NWS STORM PREDICTION CENTER NORMAN OK 0109 PM CDT SAT JUL 19 2008 AREAS AFFECTED...SE SD...NE NEB...NW IA AND SW MN CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 191809Z - 192015Z STORMS ARE EXPECTED TO DEVELOP AND INCREASE BY MID-LATE AFTERNOON ACROSS SERN SD...SW MN AND SPREAD SEWD INTO NE NEB AND NW IA. LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS...BUT ISOLATED TORNADOES CANNOT BE RULED OUT. A WW MAY BE NEEDED BY 20Z. THIS AFTERNOON A FRONTAL BOUNDARY...PARTIALLY ENHANCED BY MORNING CONVECTION EXTENDS FROM SRN MN WSWWD THROUGH SRN SD MOVING SLOWLY SEWD. THE PRE-FRONTAL WARM SECTOR IS DESTABILIZING WITH 7-7.5 C/KM 700-500 MB LAPSE RATES IN PLACE ABOVE RICH LOW LEVEL MOISTURE. MODERATE-STRONG INSTABILITY IS EXPECTED AS THE BOUNDARY LAYER CONTINUES TO WARM WITH MLCAPE RANGING FROM NEAR 3000 J/KG OVER NEB AND SERN SD TO 1500-2000 J/KG OVER MN AND IA. LATEST VISIBLE AND RADAR DATA SHOW CONVECTION INCREASING ALONG THE BOUNDARY FROM SW MN INTO SERN SD. STORMS DEVELOPING SO FAR APPEAR SHALLOW AND SLIGHTLY ELEVATED. ACARS AND FORECAST ROAB DATA SHOW PRESENCE OF AN INVERSION NEAR 700 MB. COMPLICATING FACTOR IS TENDENCY FOR THE STRONGER LARGE SCALE ASCENT ACCOMPANYING SHORTWAVE TROUGH MOVING EWD THROUGH WRN MN TO REMAIN NORTH OF WARM SECTOR. HOWEVER...AS TEMPERATURES WARM INTO THE MID 80S...CONVECTIVE INHIBITION SHOULD WEAKEN SUFFICIENTLY TO SUPPORT DEVELOPMENT OF A FEW STORMS ALONG THE BOUNDARY THIS AFTERNOON. BULKS SHEAR OF 40-50 KT ALONG WITH A FAVORABLE THERMODYNAMIC ENVIRONMENT WILL LIKELY FAVOR SUPERCELLS AND BOWING SEGMENTS WITH A THREAT OF LARGE HAIL AND DAMAGING WIND. SUFFICIENT LOW-LEVEL DIRECTIONAL SHEAR ALSO EXISTS TO SUPPORT A THREAT OF ISOLATED TORNADOES WITH ANY DISCRETE MODES. ..DIAL.. 07/19/2008 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...MPX...DMX...FSD...OAX...LBF... 43599717 43909612 44639492 44419367 43639325 42839348 42339432 41899676 42179908 43319930
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 19, 2:28 PM CDT | Tornado Watch | SPC | Buena Vista, Cherokee, Clay, Dickinson, Emmet, Harrison and 12 more | 8 hr |
| Jul 19, 5:22 PM CDT | Tornado Watch | SPC | Allamakee, Black Hawk, Boone, Bremer, Butler, Calhoun and 25 more | 5 hr |
| Jul 19, 6:56 PM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 45 more | 2 hr |
| Jul 18, 8:45 PM CDT | Mesoscale Discussion | SPC | Keya Paha | 2 hr |
| Jul 18, 9:58 PM CDT | Severe Thunderstorm Watch | SPC | Boyd, Brown, Cherry, Holt, Keya Paha, Rock | 6 hr |
| Jul 18, 11:47 PM CDT | Mesoscale Discussion | SPC | Boyd, Brown, Cherry, Holt, Keya Paha, Rock | 88 min |
Nearby
Mesoscale Discussions in Iowa, 2008Mesoscale Discussions in Minnesota, 2008Mesoscale Discussions in Nebraska, 2008Every mesoscale discussion in 2008
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.