Alert archive / Alabama / Shelby County / Tornado Warnings
Tornado Warnings in Shelby County, Alabama, 2011
17 tornado warnings in 2011. An alert counts here when it covered this county. The archive of tornado warnings reaches back to 1986.
Shelby County and its neighbors
Each county as a circle sized by its count in 2011. Tap one for its archive.
- Tornado Warnings
- 17
- Busiest month
- April10 tornado warnings
- Busiest day
- April 27, 20113 tornado warnings
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
13 of 17 tornado warnings covering Shelby County in 2011 had a tornado report inside them; 12 of 12 tornado reports fell inside a warning, on average 26 minutes after it went out.
Shelby County, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 17 | 13 | 24% | 12 | 100% | 26 min |
Each office's whole area, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Birmingham, AL: tornado warnings | 175 | 71 | 59% | 152 | 88% | 29 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
Every alert, in the order issued. Times are local, Central Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Feb 28, 3:39 PM CST | Tornado Warning | BMX | 36 min |
| Mar 26, 4:07 PM CDT | Tornado Warning | BMX | 38 min |
| Mar 26, 4:39 PM CDT | Tornado Warning | BMX | 16 min |
| Apr 11, 7:19 PM CDT | Tornado Warning | BMX | 21 min |
| Apr 11, 7:34 PM CDT | Tornado Warning | BMX | 19 min |
| Apr 15, 4:28 PM CDT | Tornado Warning | BMX | 62 min |
| Apr 15, 5:26 PM CDT | Tornado Warning | BMX | 49 min |
| Apr 27, 5:29 AM CDT | Tornado Warning | BMX | 31 min |
| Apr 27, 5:31 PM CDT | Tornado Warning | BMX | 59 min |
| Apr 27, 6:39 PM CDT | Tornado Warning | BMX | 66 min |
| Apr 27, 7:07 PM CDT | Tornado Warning | BMX | 53 min |
| Apr 27, 7:31 PM CDT | Tornado Warning | BMX | 59 min |
| Apr 27, 7:54 PM CDT | Tornado Warning | BMX | 51 min |
| Nov 16, 9:31 AM CST | Tornado Warning | BMX | 29 min |
| Dec 22, 12:53 PM CST | Tornado Warning | BMX | 52 min |
| Dec 22, 12:59 PM CST | Tornado Warning | BMX | 31 min |
| Dec 22, 1:54 PM CST | Tornado Warning | BMX | 39 min |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20102012
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.