Alert archive / Iowa / Tornado Watches in 1999

Tornado Watch 135

April 8, 199914 counties in Illinois; 32 counties in Iowa; 7 counties in Missouri

The Storm Prediction Center issued this tornado watch at Apr 8, 1999, 5:15 PM CDT for 14 counties in Illinois; 32 counties in Iowa; 7 counties in Missouri. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Apr 8, 1999, 5:15 PM CDT (22:15 UTC)
Expired
Apr 8, 1999, 9:00 PM CDT
In force
4 hr
Issued by
the Storm Prediction Center
All 53 counties

Appanoose County, IA, Benton County, IA, Cedar County, IA, Clinton County, IA, Davis County, IA, Des Moines County, IA, Hamilton County, IA, Hardin County, IA, Henry County, IA, Iowa County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Linn County, IA, Louisa County, IA, Lucas County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Muscatine County, IA, Polk County, IA, Poweshiek County, IA, Scott County, IA, Story County, IA, Tama County, IA, Van Buren County, IA, Wapello County, IA, Washington County, IA, Adams County, IL, Brown County, IL, Cass County, IL, Fulton County, IL, Hancock County, IL, Henderson County, IL, Knox County, IL, Mason County, IL, McDonough County, IL, Menard County, IL, Mercer County, IL, Rock Island County, IL, Schuyler County, IL, Warren County, IL, Adair County, MO, Clark County, MO, Knox County, MO, Lewis County, MO, Putnam County, MO, Schuyler County, MO, Scotland County, MO

The radar

The Quad Cities radar (KDVN), 87 km from the middle of the area, began a volume at 22:18 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.

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 8, 5:21 PM CDTTornado WarningLSXKnox, Shelby64 min
Apr 8, 5:37 PM CDTTornado WarningDMXMarion, Monroe33 min
Apr 8, 5:37 PM CDTTornado WarningDMXJasper33 min
Apr 8, 5:49 PM CDTTornado WarningDMXAppanoose31 min
Apr 8, 5:50 PM CDTTornado WarningLSXLewis50 min
Apr 8, 5:51 PM CDTTornado WarningDMXPolk49 min
Apr 8, 5:52 PM CDTTornado WarningDVNVan Buren48 min
Apr 8, 6:05 PM CDTTornado WarningDMXDavis35 min
Apr 8, 6:06 PM CDTTornado WarningDMXMahaska34 min
Apr 8, 6:09 PM CDTTornado WarningLSXClark46 min
Apr 8, 6:13 PM CDTTornado WarningDVNJefferson47 min
Apr 8, 6:16 PM CDTTornado WarningDMXWapello34 min
Apr 8, 6:17 PM CDTTornado WarningDVNHancock48 min
Apr 8, 6:33 PM CDTTornado WarningDVNKeokuk, Washington47 min
Apr 8, 6:40 PM CDTTornado WarningLSXLewis50 min
Apr 8, 6:58 PM CDTTornado WarningDVNHancock47 min
Apr 8, 7:08 PM CDTTornado WarningLSXAdams47 min
Apr 8, 7:15 PM CDTTornado WarningDVNHenderson, McDonough, Warren45 min
Apr 8, 7:44 PM CDTTornado WarningILXKnox46 min
Apr 8, 7:54 PM CDTTornado WarningDVNWarren46 min
Apr 8, 8:32 PM CDTTornado WarningILXFulton, Knox28 min

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 10.3 hours before the alert went out and 94 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 1999-04-08Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 1999-04-08The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 6 square meters per square second.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2467 m above ground
0-6 km bulk shear
61 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
115 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 8, 5:15 PM CDTTornado WatchSPCCalhoun, Greene, Jersey, Macoupin, Morgan, Pike and 1 more4 hr
Apr 8, 6:30 AM CDTSevere Thunderstorm WatchSPCFremont, Mills, Page6 hr
Apr 8, 11:45 AM CDTTornado WatchSPCFremont, Mills, Page5 hr
Apr 8, 1:00 PM CDTTornado WatchSPCAdair, Adams, Appanoose, Audubon, Boone, Calhoun and 33 more6 hr
Apr 8, 6:15 PM CDTTornado WatchSPCBarry, Carter, Christian, Crawford, Dallas, Dent and 19 more4 hr

Nearby

Tornado Watches in Iowa, 1999Tornado Watches in Illinois, 1999Tornado Watches in Missouri, 1999Every tornado watch in 1999

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.