Tornado Warnings in North Dakota, 2009

By month

18 of 70 tornado warnings covering North Dakota in 2009 had a tornado report inside them; 28 of 40 tornado reports fell inside a warning, on average 20 minutes after it went out.

North Dakota, 2009

Each office's whole area, 2009

An office's figures cover every county it serves, including across state lines.

Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.

• Stark County13
• Grant County7
• Burke County7
• Hettinger County6
• Billings County6
• Dunn County5
• Richland County5
• Oliver County5
• Sheridan County5
• Grand Forks County5
• McLean County5
• Adams County4
• Wells County4
• Mercer County4
• Morton County4
• Mountrail County4
• Williams County3
• Golden Valley County3
• Renville County3
• Ward County3
• Sioux County2
• McIntosh County2
• Pierce County2
• Nelson County2
• Walsh County2
• Traill County2
• McKenzie County2
• Divide County2
• Bottineau County2
• Emmons County1
• Logan County1
• Benson County1
• Pembina County1
• Steele County1
• Burleigh County1
• Towner County1
• Slope County1

1. June 26, 200917tornado warnings
2. July 9, 200916tornado warnings
3. July 12, 20099tornado warnings
4. June 27, 20096tornado warnings
5. June 18, 20095tornado warnings
6. June 25, 20095tornado warnings
7. June 16, 20093tornado warnings
8. June 22, 20092tornado warnings
9. June 17, 20091tornado warnings
10. June 23, 20091tornado warnings
11. June 24, 20091tornado warnings
12. July 4, 20091tornado warnings

Alerts in force nowTornadoes on recordThe radar archive20082010

National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.