Alert archive / North Dakota / Tornado Watches in 2009
Tornado Watch 733
The Storm Prediction Center issued this tornado watch at Aug 23, 2009, 7:55 PM MDT for 11 counties in Montana; 21 counties in North Dakota; Harding County, Perkins County, South Dakota. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 23, 2009, 7:55 PM MDT (01:55 UTC)
- Expired
- Aug 24, 2009, 1:00 AM MDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 34 counties
Carter County, MT, Daniels County, MT, Dawson County, MT, Fallon County, MT, McCone County, MT, Prairie County, MT, Richland County, MT, Roosevelt County, MT, Sheridan County, MT, Valley County, MT, Wibaux County, MT, Adams County, ND, Billings County, ND, Bowman County, ND, Burke County, ND, Divide County, ND, Dunn County, ND, Golden Valley County, ND, Grant County, ND, Hettinger County, ND, McKenzie County, ND, McLean County, ND, Mercer County, ND, Morton County, ND, Mountrail County, ND, Oliver County, ND, Renville County, ND, Sioux County, ND, Slope County, ND, Stark County, ND, Ward County, ND, Williams County, ND, Harding County, SD, Perkins County, SD
The radar
The Glasgow radar (KGGW), 207 km from the middle of the area, began a volume at 01:58 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
- 30%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 95%
Warnings issued inside it
21 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 8:02 PM MDT | Severe Thunderstorm Warning | GGW | Dawson, McCone, Richland | 58 min |
| Aug 23, 8:30 PM MDT | Severe Thunderstorm Warning | GGW | McCone, Roosevelt, Valley | 60 min |
| Aug 23, 8:59 PM MDT | Severe Thunderstorm Warning | GGW | Dawson, McCone, Richland, Roosevelt | 61 min |
| Aug 23, 9:03 PM MDT | Tornado Warning | GGW | Daniels | 42 min |
| Aug 23, 9:28 PM MDT | Severe Thunderstorm Warning | GGW | Daniels, Roosevelt, Valley | 30 min |
| Aug 23, 9:34 PM MDT | Severe Thunderstorm Warning | GGW | Dawson, McCone, Richland | 56 min |
| Aug 23, 9:41 PM MDT | Tornado Warning | GGW | Daniels, Sheridan | 40 min |
| Aug 23, 9:46 PM MDT | Severe Thunderstorm Warning | GGW | Richland, Roosevelt | 59 min |
| Aug 23, 10:17 PM MDT | Flash Flood Warning | GGW | Dawson, McCone, Richland | 3 hr |
| Aug 23, 10:20 PM MDT | Flash Flood Warning | GGW | Daniels, Sheridan | 3 hr |
| Aug 23, 10:30 PM MDT | Severe Thunderstorm Warning | BIS | McKenzie, Williams | 60 min |
| Aug 23, 10:32 PM MDT | Severe Thunderstorm Warning | GGW | Dawson, Richland, Roosevelt | 41 min |
| Aug 23, 10:42 PM MDT | Severe Thunderstorm Warning | GGW | Richland | 33 min |
| Aug 23, 10:46 PM MDT | Flash Flood Warning | GGW | Richland | 3 hr |
| Aug 23, 10:57 PM MDT | Tornado Warning | BIS | McKenzie, Williams | 33 min |
| Aug 23, 11:06 PM MDT | Flash Flood Warning | BIS | McKenzie, Williams | 5 hr |
| Aug 23, 11:08 PM MDT | Severe Thunderstorm Warning | BIS | McKenzie | 52 min |
| Aug 23, 11:15 PM MDT | Severe Thunderstorm Warning | GGW | Richland | 45 min |
| Aug 23, 11:29 PM MDT | Severe Thunderstorm Warning | BIS | McKenzie, Williams | 61 min |
| Aug 23, 11:58 PM MDT | Severe Thunderstorm Warning | BIS | McKenzie | 32 min |
| Aug 24, 12:15 AM MDT | Severe Thunderstorm Warning | BIS | Burke, Divide, McKenzie, Mountrail, Williams | 60 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
Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 1.9 hours before the alert went out and 205 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
- 1890 J/kg
- Mixed-layer CIN
- -51 J/kg
- Mixed-layer LCL
- 1908 m above ground
- 0-6 km bulk shear
- 54 kt
- 0-1 km storm-relative helicity
- 42 m²/s²
- 0-3 km storm-relative helicity
- 98 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 3.8
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 7:02 PM MDT | Mesoscale Discussion | SPC | Custer, Daniels, Dawson, Fallon, McCone, Prairie and 4 more | 88 min |
| Aug 23, 10:12 PM MDT | Mesoscale Discussion | SPC | Richland, Roosevelt, Sheridan | 93 min |
| Aug 24, 12:27 AM MDT | Mesoscale Discussion | SPC | Bottineau, Burke, Divide, McHenry, McKenzie, McLean and 6 more | 33 min |
| Aug 24, 12:48 AM MDT | Severe Thunderstorm Watch | SPC | Bottineau, Burke, Dunn, McHenry, McLean, Mercer and 6 more | 4 hr |
| Aug 24, 3:32 AM MDT | Mesoscale Discussion | SPC | Bottineau, McHenry, Pierce, Renville, Rolette | 58 min |
Nearby
Tornado Watches in North Dakota, 2009Tornado Watches in Montana, 2009Tornado Watches in South Dakota, 2009Every tornado watch in 2009
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.