Alert archive / Iowa / Severe Thunderstorm Warnings in 2003

Severe Thunderstorm Warning 221, NWS Des Moines, IA

July 20, 2003Cass County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 20, 2003, 9:27 PM CDT for Cass County, Iowa. It was in force for 33 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 20, 2003, 9:27 PM CDT (02:27 UTC)
Expired: Jul 20, 2003, 10:00 PM CDT
In force: 33 min
Issued by: NWS Des Moines, IA
Area: Counties, with a storm outline in the text

County Cass County, IA

The radar

The Des Moines radar (KDMX), 114 km from the middle of the area, began a volume at 02:26 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 20, 8:50 PM CDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.5 hours before the alert went out and 116 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: 4827 J/kg
Mixed-layer CIN: -30 J/kg
Mixed-layer LCL: 1616 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 92 m²/s²
0-3 km storm-relative helicity: 162 m²/s²
Significant tornado parameter: 1.4
Supercell composite: 28.6

Open this sounding in Storm Lab

The text

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

000 
WUUS53 KDMX 210227
SVRDMX
IAC029-210300-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
926 PM CDT SUN JUL 20 2003

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CASS COUNTY IN SOUTHWEST IOWA

* UNTIL 1000 PM CDT

* AT 921 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 5 MILES SOUTHEAST OF LEWIS...OR ABOUT 44 MILES
  EAST OF COUNCIL BLUFFS...MOVING SOUTHEAST AT 40 MPH.

* THE SEVERE THUNDERSTORM WILL BE...

  6 MILES SOUTHWEST OF MASSENA AROUND 935 PM.

AT 926 PM...AUTOMATED WEATHER STATION AT THE ATLANTIC AIRPORT 
REPORTED A WIND GUST TO 58 MPH.

VERY STRONG WINDS UP TO 60 MPH ARE LIKELY IN THE WARNED AREA.

MOVE TO AN INTERIOR ROOM AND STAY AWAY FROM WINDOWS. IF YOU LIVE IN A
MOBILE HOME...SEEK SHELTER IN A STURDY BUILDING.

A TORNADO WATCH ALSO REMAINS IN EFFECT UNTIL 200 AM MONDAY MORNING 
FOR SOUTHWESTERN IOWA.

LAT...LON 41

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 20, 3:21 PM CDT, 6 hours 6 minutes earlier.

Area forecast discussion, Jul 20, 3:21 PM CDT, 6 hours 6 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
321 PM CDT SUN JUL 20 2003

PRIMARY CONCERN WL BE SVR TSTM POTENTIAL THIS EVE.  LRG SCALE
SCENARIO HAS UPR LOW AND ASSOCD SPEED MAX PUSHING TWRD GTLKS.
SCNDRY SUBTLE TROF AND UVM EHNANCEMENT ALSO NOTED ACRS SD HELPING
BEGINNING OF TSTM DVLPMT.  19Z SFC ANLYS BTWN KMHE-KYKN WITH TWO
BNDRYS OF CONCERN.  FIRST MORE SYNOPTIC SCALE TROF/WEAK WRMFNT
EVIDENT FM LOW INTO NERN KS AND NRN MO.  SCNDRY OUTFLOW BNDRY NOTED
FM LOW INTO CNTRL IA.  OUTFLOW BNDRY HAS BEEN SLOWLY DSIPTG MOVG EWD
ALLOWING VERY UNSTABLE AMS TO BUILD INTO WRN IA.  MUCAPES IN WRM
SECTOR 3000-5000 J/KG...EVEN HIGHER FARHTER SW...WITH MINIMAL CIN
CONTG TO DMSH.  0-6KM SHEAR NOT THE GREATEST AT 35-50 KTS...BUT
CERTAINLY SUFFICIENT FOR SUPERCELLS CONSIDERING EXTREME CAPE.  COULD
SEE SUPERCELL AND ISOLD TORNADIC DVLPMT INVOF BNDRYS FOLLOWED BY
DAMAGING WND MCS DOWN INSTABILITY GRADIENT AND BNDRYS INTO MO LATER
THIS EVEN.  CIN MINIMUM NOT QUITE BUILDING FAR ENOUGH EWD YET
HWVR...SO WE MAY NOT SEE SGFNT DVLPMT FOR SVRL MORE HRS.

MDLS AGREE BRINGING FNT INTO MO AND IL BY 12Z SO TSTMS SHOULD DMSH
OVNGT FOLLOWED BY LTL OR NO PCPN FOR NEXT SVRL DAYS.  MDL QPF AND
GUIDANCE SUGGEST ADDING POPS LATE MON OR TUE...BUT CONSENSUS AMONG
SURROUNDING OFFICES WAS TO LEAVE IA MENTION OUT FOR NOW.  CANNOT
REALLY FIND MUCH OF A MECHANISM WITH BEST THERMODYNAMIC AND
KINEMATIC FORCING S AND W OF FA.  LOW LVL TEMPS SUGGEST STEADY COOL
DOWN WHICH IS REFLECTED BY GUIDANCE WHICH IS SIMILAR...SO WL FOLLOW
COMPROMISE.  THOSE TEMPS TUE ARE ONLY A FEW CATEGORIES ABV RECORD
MIN MAXES SO STAYED ON THE WRM SIDE THAT DAY.

MED RANGE MDLS IN FAIR AGREEMENT WITH CHG FM AMPLIFIED PTN AND ERN
TROF ARND MIDWEEK FOLLOWED BY RISING HGTS AND ZNL FLOW TWRD NEXT
WEEKEND.  UNFORTUNATELY THAT STILL RESULTS IN LOW FCST CONFIDENCE
WITH FA ON SRN EDGE OF WLYS AND UNCERTAINTY IN SWD PROGRESSION OF
FNTS.  GENERALLY SAW NO REASON TO DEVIATE FM GFS ENSEMBLES AND HPC
GUIDANCE.  ALTHOUGH MY CONFIDENCE AND THERMODYNAMIC SIGNAL WAS NOT
HIGH ENOUGH TO ADD TDA...WL HAVE TO WATCH ELEVATED ISENT LIFT
POTENTIAL SOMETIME ARND THU NGT.  OTRW CONT CHCS OVR WEEKEND INVOF
OF STNRY FNT.  DID TAKE SERN PTNS OUT OF THE POPS HWVR WHICH SEEM
TOO FAR REMOVED FM FNTL CNVGNC.  GENERALLY LEFT TEMPS AS IS WHICH IS
ABV GUIDANCE AND CLOSE TO CLIMO AS FA RMNS IN WRM SECTOR.

.DSM...NONE

SMALL

Hazardous weather outlook, Jul 20, 4:50 PM CDT, 4 hours 37 minutes before

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-211100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
450 PM CDT SUN JUL 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

A SLIGHT RISK OF SEVERE THUNDERSTORMS EXISTS THROUGH THE EARLY
MORNING HOURS OF MONDAY ACROSS ALL OF CENTRAL IOWA. UNSTABLE
CONDITIONS HAVE DEVELOPED ACROSS CENTRAL IOWA THIS AFTERNOON AND
WILL SUPPORT SEVERE THUNDERSTORM DEVELOPMENT THIS EVENING ACROSS
NORTHERN AND WESTERN IOWA.  THESE STORMS WILL MOVE SOUTHEAST THROUGH
THE STATE AND SHOULD EXIT SOUTHERN IOWA BY EARLY MONDAY MORNING.
THE MAIN THREAT FROM THESE STORMS WILL BE LARGE HAIL AND DAMAGING
WINDS...HOWEVER AN ISOLATED TORNADO IS POSSIBLE THIS EVENING...
MAINLY WEST OF A SAC CITY TO MOUNT AYR LINE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THUNDERSTORMS ARE EXPECTED ACROSS PORTIONS OF NORTHERN AND WESTERN
IOWA NEXT SATURDAY.  AT THIS TIME...THE SEVERE WEATHER POTENTIAL CAN
NOT BE DETERMINED.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

IT IS LIKELY THAT CENTRAL IOWA SKYWARN AND OTHER ORGANIZED SPOTTER
GROUPS WILL BE NEEDED THIS EVENING INTO THE OVERNIGHT TO ASSIST THE
NATIONAL WEATHER SERVICE.

&&

MORE INFORMATION CAN BE OBTAINED AT WWW.CRH.NOAA.GOV/DMX (ALL LOWER CASE).

COGIL

In the hours before

Local storm report, Jul 20, 7:36 PM CDT, 1 hour 51 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
0736 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0725 PM    5 E ODEBOLT               IA   1.00 IN HAIL
07/20/03   SAC                            REPORTED BY TRAINED STORM
                                          SPOTTER.

0732 PM    4 N EARLY                 IA   0.88 IN HAIL
07/20/03   SAC                            REPORTED BY TRAINED STORM
                                          SPOTTER.

MR

Local storm report, Jul 20, 8:53 PM CDT, 34 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
0853 PM CDT SUN JUL 20 2003

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0840 PM    LATIMER                   IA   1.75 IN HAIL
07/20/03   FRANKLIN                       REPORTED BY TRAINED
                                          SPOTTER.

0845 PM    3 E LATIMER               IA   2.50 IN HAIL
07/20/03   FRANKLIN                       REPORTED BY TRAINED
                                          SPOTTER.

BF

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 7:29 PM CDT	Severe Thunderstorm Warning	DMX	Sac	46 min
Jul 20, 8:35 PM CDT	Severe Thunderstorm Warning	DMX	Franklin	40 min
Jul 20, 8:59 PM CDT	Severe Thunderstorm Warning	DMX	Butler	46 min
Jul 20, 9:05 PM CDT	Severe Thunderstorm Warning	DMX	Bremer	55 min
Jul 20, 9:20 PM CDT	Severe Thunderstorm Warning	DMX	Black Hawk	40 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2003 Every severe thunderstorm warning in 2003

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.