Tornado Warnings in South Dakota, 2009

By month

28 of 91 tornado warnings covering South Dakota in 2009 had a tornado report inside them; 32 of 38 tornado reports fell inside a warning, on average 19 minutes after it went out.

South 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.

• Todd County8
• Hand County8
• Aurora County8
• McCook County8
• Davison County7
• Hanson County7
• Hutchinson County7
• Sanborn County6
• Douglas County6
• Turner County6
• Miner County6
• Tripp County5
• Bon Homme County5
• Faulk County5
• Beadle County5
• Yankton County5
• Meade County4
• Stanley County4
• Haakon County4
• Jerauld County4
• Brookings County4
• Kingsbury County4
• Mellette County4
• Charles Mix County4
• Jackson County4
• Potter County3
• Clay County3
• Gregory County3
• Lake County3
• Moody County3
• Pennington County3
• Minnehaha County3
• Perkins County2
• Ziebach County2
• Butte County2
• Campbell County2
• McPherson County2
• Day County2
• Brule County2
• Edmunds County1

1. June 16, 200926tornado warnings
2. June 25, 200915tornado warnings
3. August 8, 20098tornado warnings
4. July 13, 20097tornado warnings
5. July 9, 20096tornado warnings
6. June 17, 20095tornado warnings
7. June 14, 20093tornado warnings
8. June 19, 20093tornado warnings
9. July 7, 20093tornado warnings
10. July 8, 20093tornado warnings
11. March 23, 20092tornado warnings
12. May 12, 20092tornado 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.