Alert archive / Iowa / Tornado Watches in 1998

Tornado Watch 466

May 30, 199837 counties in Iowa

The Storm Prediction Center issued this tornado watch at May 30, 1998, 1:00 PM CDT for 37 counties in Iowa. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
May 30, 1998, 1:00 PM CDT (18:00 UTC)
Expired
May 30, 1998, 5:00 PM CDT
In force
4 hr
Issued by
the Storm Prediction Center
All 37 counties

Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clayton County, IA, Dallas County, IA, Delaware County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Iowa County, IA, Jasper County, IA, Johnson County, IA, Keokuk County, IA, Kossuth County, IA, Linn County, IA, Louisa County, IA, Mahaska County, IA, Marshall County, IA, Polk County, IA, Poweshiek County, IA, Story County, IA, Tama County, IA, Washington County, IA, Webster County, IA, Wright County, IA

Warnings issued inside it

9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
May 30, 1:05 PM CDTSevere Thunderstorm WarningDMXBoone50 min
May 30, 1:25 PM CDTTornado WarningDMXBoone35 min
May 30, 1:34 PM CDTSevere Thunderstorm WarningDMXStory51 min
May 30, 1:50 PM CDTTornado WarningDMXBoone50 min
May 30, 2:12 PM CDTSevere Thunderstorm WarningDMXMarshall48 min
May 30, 2:20 PM CDTTornado WarningDMXMarshall50 min
May 30, 2:52 PM CDTSevere Thunderstorm WarningDMXTama48 min
May 30, 3:08 PM CDTTornado WarningDMXMarshall22 min
May 30, 3:08 PM CDTTornado WarningDMXMarshall17 min

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 6.0 hours before the alert went out and 247 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-pSkew-T log-p diagram, Davenport, at 12:00Z on 1998-05-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 616 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 12:00Z on 1998-05-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 64 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
616 J/kg
Mixed-layer CIN
-69 J/kg
Mixed-layer LCL
1133 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
64 m²/s²
0-3 km storm-relative helicity
3 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.9

Open this sounding in Storm Lab

The text

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

533 
WWUS9 KMKC 301738
SEL6  
MKC WW 301738
IAZ000-302200-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 466
STORM PREDICTION CENTER NORMAN OK
1238 PM CDT SAT MAY 30 1998

THE STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

   CENTRAL AND EASTERN IOWA                               

EFFECTIVE THIS SATURDAY AFTERNOON FROM 100 PM UNTIL 500 PM CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 65 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 20 MILES WEST OF FORT DODGE IOWA TO 25 MILES
EAST NORTHEAST OF CEDAR RAPIDS 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...THIS TORNADO WATCH REPLACES SEVERE
THUNDERSTORM WATCH NUMBER 465.  WATCH NUMBER 465 WILL NOT BE IN
EFFECT AFTER 100 PM CDT.

DISCUSSION...CLUSTER OF STORMS OVER NW IA HAS EVOLVED INTO A
SUPERCELL. ALTHOUGH THERE IS NO READILY IDENTIFIABLE BOUNDARY FOR
THE STORM TO MOVE ALONG...STRONGLY DEVIANT STORM MOTION OF 280
DEGREES AT 30 KT IS RESULTING IN FAVORABLE STORM RELATIVE FLOW AND
HELICITY FOR TORNADOES. 


AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. 
MEAN STORM MOTION VECTOR 28030.


...VESCIO

432,0943 425,0911 410,0911 413,0943

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 30, 12:00 PM CDTSevere Thunderstorm WatchSPCAllamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 31 more5 hr

Nearby

Tornado Watches in Iowa, 1998Every tornado watch 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; the sounding from the Mesonet's radiosonde archive.