Alert archive / Iowa / Tornado Watches in 2018
Tornado Watch 367
The Storm Prediction Center issued this tornado watch at Sep 3, 2018, 6:09 PM CDT for 12 counties in Iowa. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 3, 2018, 6:09 PM CDT (23:09 UTC)
- Expired
- Sep 3, 2018, 8:37 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
Counties Benton County, IA, Black Hawk County, IA, Buchanan County, IA, Delaware County, IA, Dubuque County, IA, Iowa County, IA, Jackson County, IA, Jones County, IA, Linn County, IA, Mahaska County, IA, Poweshiek County, IA, Tama County, IA
The radar
The Quad Cities radar (KDVN), 124 km from the middle of the area, began a volume at 23:11 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 SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 40%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 20%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 50%
Warnings issued inside it
3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 3, 6:21 PM CDT | Severe Thunderstorm Warning | DVN | Delaware, Dubuque | 39 min |
| Sep 3, 6:58 PM CDT | Tornado Warning | DMX | Poweshiek | 32 min |
| Sep 3, 7:43 PM CDT | Flash Flood Warning | DMX | Black Hawk | 3 hr |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Davenport, (KDVN), launched 12:00Z, 11.2 hours before the alert went out and 130 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.
- Mixed-layer CAPE
- 1178 J/kg
- Mixed-layer CIN
- -30 J/kg
- Mixed-layer LCL
- 851 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 118 m²/s²
- 0-3 km storm-relative helicity
- 107 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 2.5
The text
As transmitted.
513 WWUS20 KWNS 032306 SEL7 SPC WW 032306 IAZ000-040300- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 367 NWS Storm Prediction Center Norman OK 610 PM CDT Mon Sep 3 2018 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Small part of central and northeastern Iowa * Effective this Monday evening from 610 PM until 1000 PM CDT. * Primary threats include... A couple tornadoes possible Isolated damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...A narrow corridor of tornado threat is expected to persist for a few more hours this evening, where supercells interact with a slow-moving warm front. A couple of tornadoes will be possible prior to gradual stabilization of the low levels by early tonight. The tornado watch area is approximately along and 30 statute miles north and south of a line from 65 miles west southwest of Cedar Rapids IA to 15 miles north northeast of Dubuque IA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). PRECAUTIONARY/PREPAREDNESS ACTIONS... 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...CONTINUE...WW 366... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25025. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 3, 1:20 PM CDT | Mesoscale Discussion | SPC | Cedar, Clinton, Des Moines, Henry, Iowa, Jackson and 9 more | 2 hr |
| Sep 3, 5:47 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Benton, Black Hawk, Boone, Bremer and 39 more | 58 min |
Nearby
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.