Alert archive / Iowa / Tornado Watches in 2007
Tornado Watch 564
The Storm Prediction Center issued this tornado watch at Aug 4, 2007, 7:42 PM CDT for 22 counties in Iowa. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 4, 2007, 7:42 PM CDT (00:42 UTC)
- Expired
- Aug 4, 2007, 11:00 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 22 counties
Audubon County, IA, Boone County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cherokee County, IA, Crawford County, IA, Dallas County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Humboldt County, IA, Ida County, IA, Jasper County, IA, Marshall County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Sac County, IA, Story County, IA, Webster County, IA
The radar
The Des Moines radar (KDMX), 100 km from the middle of the area, began a volume at 00:41 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 40%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 10:58 PM CDT | Flash Flood Warning | DMX | Calhoun, Webster | 4 hr |
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 00:00Z, 0.7 hours before the alert went out and 169 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
- 1034 J/kg
- Mixed-layer CIN
- -47 J/kg
- Mixed-layer LCL
- 1889 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 12 m²/s²
- 0-3 km storm-relative helicity
- 73 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.8
The text
As transmitted, in the capitals the NWS used until 2016.
000
WWUS20 KWNS 050040
SEL4
SPC WW 050040
IAZ000-050400-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 564
NWS STORM PREDICTION CENTER NORMAN OK
740 PM CDT SAT AUG 4 2007
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
NORTHWEST INTO CENTRAL IOWA
EFFECTIVE THIS SATURDAY EVENING FROM 740 PM UNTIL 1100 PM CDT.
TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE
MILES EAST AND WEST OF A LINE FROM 10 MILES NORTH OF STORM LAKE
IOWA TO 15 MILES EAST SOUTHEAST OF DES MOINES IOWA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU4).
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 562...WW 563...
DISCUSSION...THUNDERSTORMS INCREASING OVER NWRN IA EARLY THIS
EVENING INVOF SURFACE LOW. SHEAR REMAINS QUITE STRONG ACROSS THIS
REGION... ESPECIALLY SEWD ALONG WARM FRONT INTO CENTRAL IA. GIVEN
PERSISTENT MODERATE TO STRONG INSTABILITY...STORMS SHOULD CONTINUE
MOVING SSEWD IN THE FORM OR DISCRETE SUPERCELLS THIS EVENING.
ENHANCED LOW LEVEL SHEAR AND VERY MOIST BOUNDARY LAYER WILL SUPPORT
A RISK OF TORNADOES INTO THIS AREA.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 32020.
...EVANSSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 9:07 PM CDT | Mesoscale Discussion | SPC | Harrison, Monona, Pottawattamie | 53 min |
| Aug 4, 9:22 PM CDT | Mesoscale Discussion | SPC | Audubon, Boone, Buena Vista, Calhoun, Carroll, Cherokee and 15 more | 53 min |
| Aug 5, 3:54 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Benton, Cass, Cedar and 39 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.