Alert archive / Iowa / Tornado Watches in 2020
Tornado Watch 229
The Storm Prediction Center issued this tornado watch at May 26, 2020, 1:20 PM CDT for 58 counties in Iowa. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- May 26, 2020, 1:20 PM CDT (18:20 UTC)
- Expired
- May 26, 2020, 8:00 PM CDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 58 counties
Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clarke County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Emmet 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, Howard County, IA, Humboldt County, IA, Iowa County, IA, Jasper County, IA, Jefferson County, IA, Keokuk County, IA, Kossuth County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Mitchell County, IA, Monroe County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Ringgold County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Van Buren County, IA, Wapello County, IA, Warren County, IA, Wayne County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA
The radar
The Des Moines radar (KDMX), 81 km from the middle of the area, began a volume at 18:20 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
- 40%
- 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
- 20%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
10 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 26, 1:25 PM CDT | Tornado Warning | DMX | Dallas | 35 min |
| May 26, 1:44 PM CDT | Severe Thunderstorm Warning | DVN | Henry, Jefferson, Keokuk, Washington | 31 min |
| May 26, 1:49 PM CDT | Tornado Warning | DMX | Boone, Dallas | 26 min |
| May 26, 2:01 PM CDT | Severe Thunderstorm Warning | DVN | Benton, Iowa, Johnson | 32 min |
| May 26, 2:22 PM CDT | Tornado Warning | DMX | Poweshiek, Tama | 38 min |
| May 26, 2:25 PM CDT | Tornado Warning | DMX | Boone, Webster | 35 min |
| May 26, 3:47 PM CDT | Tornado Warning | DMX | Humboldt, Wright | 13 min |
| May 26, 3:57 PM CDT | Tornado Warning | DMX | Audubon, Guthrie | 21 min |
| May 26, 5:16 PM CDT | Tornado Warning | DMX | Franklin, Wright | 29 min |
| May 26, 6:30 PM CDT | Severe Thunderstorm Warning | DMX | Worth | 30 min |
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, 6.3 hours before the alert went out and 241 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
- 332 J/kg
- Mixed-layer CIN
- -88 J/kg
- Mixed-layer LCL
- 1121 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 80 m²/s²
- 0-3 km storm-relative helicity
- 73 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
680 WWUS20 KWNS 261817 SEL9 SPC WW 261817 IAZ000-270100- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 229 NWS Storm Prediction Center Norman OK 120 PM CDT Tue May 26 2020 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central Iowa * Effective this Tuesday afternoon and evening from 120 PM until 800 PM CDT. * Primary threats include... A couple tornadoes possible Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Thunderstorms forming over southern Iowa and northern Missouri will track northward across the watch area, posing a localized risk of brief tornadoes and gusty/damaging winds. The tornado watch area is approximately along and 70 statute miles east and west of a line from 30 miles north northwest of Mason City IA to 25 miles east of Lamoni IA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). 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. && 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 18030. ...Hart
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 26, 12:29 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Boone, Clarke, Dallas and 24 more | 2 hr |
| May 26, 3:53 PM CDT | Mesoscale Discussion | SPC | Adair, Boone, Butler, Calhoun, Cerro Gordo, Dallas and 24 more | 67 min |
| May 26, 6:02 PM CDT | Mesoscale Discussion | SPC | Allamakee, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 10 more | 88 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.