Alert archive / Iowa / Tornado Warnings in 1998

Tornado Warning 4, NWS Des Moines, IA

April 6, 1998Boone County, Hamilton County, Webster County, Iowa

NWS Des Moines, IA issued this tornado warning at Apr 6, 1998, 7:36 PM CDT for Boone County, Hamilton County, Webster County, Iowa. It was in force for 34 min. 2 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: Apr 6, 1998, 7:36 PM CDT (00:36 UTC)
Expired: Apr 6, 1998, 8:10 PM CDT
In force: 34 min
Issued by: NWS Des Moines, IA
Area: Whole counties

Counties Boone County, IA, Hamilton County, IA, Webster County, IA

The radar

The Des Moines radar (KDMX), 64 km from the middle of the area, began a volume at 00:39 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	Remark
Apr 6, 7:44 PM CDT	Hail 0.75	Dayton, IA
Apr 6, 7:45 PM CDT	Hail 0.75	Dayton, 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
Apr 6, 6:30 PM CDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 0.6 hours before the alert went out and 228 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: 25 J/kg
Mixed-layer CIN: -306 J/kg
Mixed-layer LCL: 711 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 158 m²/s²
0-3 km storm-relative helicity: 414 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

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

557 
WFUS1 KDSM 070037 RRA
TORDSM
IAC015-079-187-070110-

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

* TORNADO WARNING FOR
  NORTHERN BOONE COUNTY - CENTRAL IOWA
  SOUTHERN HAMILTON COUNTY - CENTRAL IOWA
  SOUTHEASTERN WEBSTER COUNTY - CENTRAL IOWA

* UNTIL 810 PM CDT
 
* SOME AREAS AFFECTED
    DAYTON
    BOXHOLM
    STRATFORD

* AT 735 PM CDT RADAR INDICATED A TORNADO NEAR DAYTON OR 20 MILES SE OF
  FORT DODGE MOVING EAST AT 30 MPH.

* THE STORM WILL BE NEAR STRATFORD AT 755 PM CDT.

IF YOU ARE NEAR THIS DANGEROUS STORM...TAKE COVER IMMEDIATELY IN THE
LOWEST FLOOR AND INNER MOST ROOM OF A BUILDING.

FAB

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 6, 8:13 PM CDT	Tornado Warning	DMX	Boone, Greene	32 min
Apr 6, 9:13 PM CDT	Severe Thunderstorm Warning	DMX	Boone, Story	32 min

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.