Alert archive / Iowa / Tornado Warnings in 1998

Tornado Warning 59, NWS Des Moines, IA

July 6, 1998Polk County, Iowa

NWS Des Moines, IA issued this tornado warning at Jul 6, 1998, 9:35 PM CDT for Polk County, Iowa. It was in force for 35 min. 3 reports came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Jul 6, 1998, 9:35 PM CDT (02:35 UTC)
Expired: Jul 6, 1998, 10:10 PM CDT
In force: 35 min
Issued by: NWS Des Moines, IA
Area: Whole counties

County Polk County, IA

The radar

The Des Moines radar (KDMX), 13 km from the middle of the area, began a volume at 02:35 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 was reported inside it

Time	Report	Where
Jul 6, 9:36 PM CDT	Thunderstorm Wind 55	Ankeny, IA
Jul 6, 9:54 PM CDT	Thunderstorm Wind 55	Ankeny, IA
Jul 6, 10:05 PM CDT	Thunderstorm Wind 52	Des Moines, IA

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

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 6, 7:30 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.6 hours before the alert went out and 236 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: 5400 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 1040 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 77 m²/s²
0-3 km storm-relative helicity: 110 m²/s²
Significant tornado parameter: 3.7
Supercell composite: 14.8

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KDSM 070235 RRA
TORDSM
IAC153-070310-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
935 PM CDT MON JUL 6 1998

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* TORNADO WARNING FOR...
  POLK COUNTY IN CENTRAL IOWA

* UNTIL 1010 PM CDT

* AT 934 PM CDT...DOPPLER RADAR INDICATED A TORNADO 5 MILES EAST
  NORTHEAST OF DES MOINES OR 3 MILES WEST OF ALTOONA MOVING EAST AT
  30 MPH.

* THIS TORNADO CAN BE EXPECTED NEfAR...
   DES MOINES         NOW
   ALTOONA            BY 932 PM CDT
   BONDURANT          BY 932 PM CDT
   MITCHELLVILLE      BY 944 PM CDT

GO TO THE BASEMENT OR A SMALL INTERIOR ROOM ON THE LOWEST FLOOR!

JJ/BS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 6, 7:22 PM CDT	Tornado Warning	DMX	Carroll	33 min
Jul 6, 8:15 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Guthrie	35 min
Jul 6, 8:46 PM CDT	Flash Flood Warning	DMX	Dallas	3 hr
Jul 6, 8:54 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Polk	36 min
Jul 6, 9:14 PM CDT	Flash Flood Warning	DMX	Guthrie	6 hr
Jul 6, 9:20 PM CDT	Severe Thunderstorm Warning	DMX	Story	35 min
Jul 6, 9:21 PM CDT	Flash Flood Warning	DMX	Polk	6 hr
Jul 6, 9:29 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Polk	46 min
Jul 6, 9:45 PM CDT	Severe Thunderstorm Warning	DMX	Marion, Warren	45 min
Jul 6, 10:00 PM CDT	Tornado Warning	DMX	Marion	35 min
Jul 6, 10:15 PM CDT	Severe Thunderstorm Warning	DMX	Jasper	35 min
Jul 6, 10:37 PM CDT	Severe Thunderstorm Warning	DMX	Marion	33 min
Jul 6, 11:41 PM CDT	Flash Flood Warning	DMX	Dallas	3 hr

Nearby

Tornado Warnings in Iowa, 1998 Every tornado warning in 1998 Tornadoes in 1998

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.