Alert archive / Wisconsin / Tornado Watches in 2021
Tornado Watch 509
The Storm Prediction Center issued this tornado watch at Sep 20, 2021, 5:14 PM CDT for 6 counties in Wisconsin. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 20, 2021, 5:14 PM CDT (22:14 UTC)
- Expired
- Sep 20, 2021, 8:10 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
Counties Ashland County, WI, Bayfield County, WI, Iron County, WI, Price County, WI, Sawyer County, WI, Washburn County, WI
The radar
The Duluth radar (KDLH), 127 km from the middle of the area, began a volume at 22:19 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
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 50%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 20, 5:24 PM CDT | Tornado Warning | DLH | Bayfield | 36 min |
| Sep 20, 5:29 PM CDT | Tornado Warning | DLH | Bayfield | 31 min |
| Sep 20, 5:52 PM CDT | Tornado Warning | DLH | Ashland, Bayfield | 23 min |
| Sep 20, 5:57 PM CDT | Severe Thunderstorm Warning | DLH | Ashland, Bayfield, Iron, Sawyer | 63 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
Minneapolis, MN (KMPX), launched 12:00Z, 10.2 hours before the alert went out and 277 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
- 148 J/kg
- Mixed-layer CIN
- -141 J/kg
- Mixed-layer LCL
- 1002 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 210 m²/s²
- 0-3 km storm-relative helicity
- 162 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.4
The text
As transmitted.
113 WWUS20 KWNS 202210 SEL9 SPC WW 202210 WIZ000-LSZ000-210600- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 509 NWS Storm Prediction Center Norman OK 515 PM CDT Mon Sep 20 2021 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Northwest Wisconsin Lake Superior * Effective this Monday afternoon and Tuesday morning from 515 PM until 100 AM CDT. * Primary threats include... A couple tornadoes possible Isolated damaging wind gusts to 70 mph possible SUMMARY...A couple of tornadoes and a few damaging gusts will be possible this evening with circulations embedded in a squall line. The tornado watch area is approximately along and 45 statute miles east and west of a line from 25 miles north of Kennedy WI to 75 miles south of Kennedy WI. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 507...WW 508... 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 450. Mean storm motion vector 23035. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 20, 12:38 PM CDT | Mesoscale Discussion | SPC | Buffalo, Crawford, Grant, La Crosse, Pepin, Pierce and 2 more | 2 hr |
| Sep 20, 2:07 PM CDT | Severe Thunderstorm Watch | SPC | Barron, Buffalo, Chippewa, Clark, Crawford, Dunn and 14 more | 7 hr |
| Sep 20, 3:55 PM CDT | Mesoscale Discussion | SPC | Barron, Buffalo, Burnett, Chippewa, Clark, Crawford and 18 more | 95 min |
| Sep 20, 5:52 PM CDT | Mesoscale Discussion | SPC | Ashland, Barron, Bayfield, Buffalo, Chippewa, Clark and 20 more | 113 min |
Nearby
Tornado Watches in Wisconsin, 2021Every tornado watch in 2021
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.