Weather alerts in South Dakota, 2008
1,723 weather alerts in 2008, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered any part of the state, so the counties below add up to more than the state.
Weather alerts by county
Each county as a circle sized by its count in 2008. Tap one for its archive.
- Alerts
- 1,723
- Warnings
- 1,085
- Watches
- 140
- Advisories
- 289
- Busiest month
- June548 alerts
- Busiest day
- June 5, 200862 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
22 of 74 tornado warnings covering South Dakota in 2008 had a tornado report inside them; 29 of 35 tornado reports fell inside a warning, on average 13 minutes after it went out.
South Dakota, 2008
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 74 | 22 | 70% | 35 | 83% | 13 min |
| Severe thunderstorm warnings | 844 | 424 | 50% | 688 | 85% | 25 min |
| Flash flood warnings | 40 | 19 | 53% | 43 | 84% | 81 min |
Each office's whole area, 2008
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Aberdeen, SD: tornado warnings | 29 | 7 | 76% | 14 | 71% | 14 min |
| NWS Aberdeen, SD: severe thunderstorm warnings | 259 | 122 | 53% | 247 | 79% | 22 min |
| NWS Aberdeen, SD: flash flood warnings | 9 | 4 | 56% | 6 | 67% | 41 min |
| NWS Sioux Falls, SD: tornado warnings | 55 | 19 | 65% | 49 | 90% | 14 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 296 | 130 | 56% | 253 | 82% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 28 | 20 | 29% | 44 | 89% | 88 min |
| NWS Rapid City, SD: tornado warnings | 20 | 8 | 60% | 11 | 73% | 15 min |
| NWS Rapid City, SD: severe thunderstorm warnings | 496 | 269 | 46% | 410 | 90% | 28 min |
| NWS Rapid City, SD: flash flood warnings | 13 | 1 | 92% | 2 | 50% | 93 min |
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.
The alerts
1,723 alerts are too many to list on one page. Narrow it to a product above, to a month in the chart, or to a county.
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Pennington County291
- Meade County279
- Custer County222
- Lawrence County212
- Butte County190
- Dewey County175
- Haakon County169
- Ziebach County168
- Perkins County162
- Corson County162
- Charles Mix County157
- Turner County157
- Fall River County157
- Harding County156
- Hutchinson County156
- Lincoln County153
- Hand County152
- Edmunds County151
- Jackson County150
- Tripp County150
- Spink County149
- Lyman County149
- Union County148
- Yankton County148
- Stanley County147
- McPherson County146
- Gregory County145
- Brown County144
- Hyde County143
- Faulk County142
- Clay County142
- Hughes County142
- McCook County140
- Minnehaha County140
- Campbell County138
- Walworth County138
- Bon Homme County138
- Davison County138
- Douglas County138
- Sully County138
26 more counties
- Aurora County137
- Bennett County136
- Hanson County135
- Potter County135
- Mellette County134
- Marshall County133
- Beadle County132
- Todd County132
- Roberts County131
- Day County130
- Brookings County130
- Grant County129
- Brule County129
- Clark County128
- Jerauld County127
- Sanborn County127
- Jones County127
- Buffalo County127
- Moody County125
- Hamlin County123
- Lake County123
- Codington County122
- Miner County120
- Deuel County118
- Kingsbury County112
- Oglala Lakota County93
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20072009
Sources
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.