Alert archive / Iowa / Tornado Watches in 2004
Tornado Watch 224
The Storm Prediction Center issued this tornado watch at May 20, 2004, 5:00 PM CDT for 29 counties in Iowa. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- May 20, 2004, 5:00 PM CDT (22:00 UTC)
- Expired
- May 20, 2004, 10:00 PM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
All 29 counties
Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Cass County, IA, Clarke County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Fremont County, IA, Guthrie County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Monroe County, IA, Montgomery County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Ringgold County, IA, Shelby County, IA, Taylor County, IA, Union County, IA, Wapello County, IA, Warren County, IA, Wayne County, IA
The radar
The Des Moines radar (KDMX), 70 km from the middle of the area, began a volume at 22:03 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.
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 20, 5:19 PM CDT | Severe Thunderstorm Warning | DMX | Clarke | 41 min |
| May 20, 6:21 PM CDT | Severe Thunderstorm Warning | DMX | Lucas | 54 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Omaha, NE (KOAX), launched 12:00Z, 10.0 hours before the alert went out and 172 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
- 903 J/kg
- Mixed-layer CIN
- -402 J/kg
- Mixed-layer LCL
- 915 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- -34 m²/s²
- 0-3 km storm-relative helicity
- 157 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
000
WWUS20 KWNS 202158
SEL4
SPC WW 202200
IAZ000-210300-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 224
NWS STORM PREDICTION CENTER NORMAN OK
500 PM CDT THU MAY 20 2004
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
SOUTHWEST IOWA
EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 500 PM UNTIL
1000 PM CDT.
TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS ALONG AND 45 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 5 MILES NORTHEAST OF OTTUMWA IOWA TO 95 MILES
WEST NORTHWEST OF LAMONI IOWA.
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.
OTHER WATCH INFORMATION...CONTINUE...WW 222...WW 223...
DISCUSSION...VERY UNSTABLE AIR MASS ALONG E/W FRONTAL ZONE ACROSS
SRN IA. CAP HAS WEAKENED SUFFICIENTLY TO ALLOW RAPID SEVERE
THUNDERSTORM DEVELOPMENT. WITH 40-50KT DEEP LAYER SHEAR AND LOW
LCLS POTENTIAL FOR ISOLATED TORNADOES ALONG WITH LARGE HAIL WITH
ANY SUPERCELLS THAT DEVELOP.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600.
MEAN STORM MOTION VECTOR 26025.
...HALES
402,0922 402,0953 414,0953 414,0922SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 19, 7:12 PM CDT | Mesoscale Discussion | SPC | Audubon, Calhoun, Carroll, Emmet, Floyd, Franklin and 15 more | 2 hr |
| May 20, 11:31 AM CDT | Mesoscale Discussion | SPC | Adair, Benton, Black Hawk, Boone, Buchanan, Cedar and 37 more | 2 hr |
| May 20, 3:35 PM CDT | Severe Thunderstorm Watch | SPC | Benton, Black Hawk, Buchanan, Cedar, Clinton, Delaware and 15 more | 6 hr |
| May 20, 4:54 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Audubon, Boone, Cass and 33 more | 96 min |
Nearby
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.