Alert archive / Tennessee / Williamson County
Weather alerts in Williamson County, Tennessee, 2009
170 weather alerts in 2009, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Williamson County and its neighbors
Each county as a circle sized by its count in 2009. Tap one for its archive.
- Alerts
- 170
- Warnings
- 70
- Watches
- 44
- Advisories
- 22
- Busiest month
- April35 alerts
- Busiest day
- April 10, 200917 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
2 of 7 tornado warnings covering Williamson County in 2009 had a tornado report inside them.
Williamson County, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 7 | 2 | 71% | 0 | ||
| Severe thunderstorm warnings | 51 | 15 | 71% | 6 | 50% | 29 min |
| Flash flood warnings | 5 | 0 | 100% | 0 |
Each office's whole area, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Nashville, TN: tornado warnings | 106 | 18 | 83% | 34 | 85% | 15 min |
| NWS Nashville, TN: severe thunderstorm warnings | 329 | 84 | 74% | 227 | 59% | 20 min |
| NWS Nashville, TN: flash flood warnings | 78 | 23 | 71% | 44 | 70% | 85 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 |
|---|---|---|---|
| Jan 5, 4:05 AM CST | Flood Watch | OHX | 31 hr |
| Jan 6, 11:18 AM CST | Areal Flood Advisory | OHX | 10 hr |
| Jan 27, 8:40 AM CST | Areal Flood Advisory | OHX | 24 hr |
| Jan 27, 3:08 PM CST | Winter Weather Advisory | OHX | 20 hr |
| Feb 10, 3:58 PM CST | Wind Advisory | OHX | 28 hr |
| Feb 11, 10:02 AM CST | Mesoscale Discussion | SPC | 88 min |
| Feb 11, 10:38 AM CST | Tornado Watch | SPC | 6 hr |
| Feb 11, 11:05 AM CST | Severe Thunderstorm Warning | OHX | 55 min |
| Feb 11, 11:39 AM CST | Severe Thunderstorm Warning | OHX | 66 min |
| Feb 18, 11:09 AM CST | Tornado Watch | SPC | 6 hr |
| Feb 27, 3:58 AM CST | Severe Thunderstorm Watch | SPC | 119 min |
| Feb 27, 4:02 AM CST | Severe Thunderstorm Warning | OHX | 43 min |
| Feb 27, 8:24 AM CST | Areal Flood Advisory | OHX | 3 hr |
| Feb 28, 4:43 AM CST | Winter Weather Advisory | OHX | 25 hr |
| Mar 11, 4:11 PM CDT | Winter Weather Advisory | OHX | 34 hr |
| Mar 17, 1:03 AM CDT | Dense Fog Advisory | OHX | 8 hr |
| Mar 27, 2:42 PM CDT | Flood Watch | OHX | 30 hr |
| Mar 28, 12:58 PM CDT | Mesoscale Discussion | SPC | 92 min |
| Mar 28, 2:23 PM CDT | Tornado Watch | SPC | 7 hr |
| Mar 28, 4:18 PM CDT | Severe Thunderstorm Warning | OHX | 42 min |
| Mar 28, 4:56 PM CDT | Severe Thunderstorm Warning | OHX | 32 min |
| Mar 28, 5:11 PM CDT | Severe Thunderstorm Warning | OHX | 34 min |
| Mar 28, 5:18 PM CDT | Mesoscale Discussion | SPC | 57 min |
| Mar 28, 5:19 PM CDT | Tornado Warning | OHX | 26 min |
| Mar 28, 5:37 PM CDT | Severe Thunderstorm Warning | OHX | 23 min |
| Mar 28, 5:40 PM CDT | Severe Thunderstorm Warning | OHX | 35 min |
| Mar 28, 5:41 PM CDT | Tornado Warning | OHX | 35 min |
| Mar 28, 5:51 PM CDT | Severe Thunderstorm Warning | OHX | 24 min |
| Mar 28, 6:09 PM CDT | Severe Thunderstorm Warning | OHX | 36 min |
| Apr 2, 1:33 PM CDT | Tornado Watch | SPC | 5 hr |
| Apr 2, 2:46 PM CDT | Severe Thunderstorm Warning | OHX | 29 min |
| Apr 2, 3:30 PM CDT | Tornado Warning | OHX | 15 min |
| Apr 2, 3:46 PM CDT | Severe Thunderstorm Warning | OHX | 29 min |
| Apr 2, 3:53 PM CDT | Flash Flood Warning | OHX | 37 min |
| Apr 2, 4:08 PM CDT | Flash Flood Warning | OHX | 7 hr |
| Apr 2, 4:37 PM CDT | Areal Flood Warning | OHX | 3 hr |
| Apr 2, 4:43 PM CDT | Severe Thunderstorm Warning | OHX | 32 min |
| Apr 2, 6:02 PM CDT | Tornado Watch | SPC | 7 hr |
| Apr 5, 5:37 PM CDT | Tornado Watch | SPC | 5 hr |
| Apr 5, 6:19 PM CDT | Mesoscale Discussion | SPC | 86 min |
| Apr 5, 10:31 PM CDT | Freeze Watch | OHX | 5 hr |
| Apr 5, 10:31 PM CDT | Freeze Watch | OHX | 5 hr |
| Apr 6, 3:56 AM CDT | Freeze Warning | OHX | 29 hr |
| Apr 6, 3:56 AM CDT | Freeze Warning | OHX | 51 hr |
| Apr 10, 12:50 AM CDT | Mesoscale Discussion | SPC | 85 min |
| Apr 10, 1:22 AM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Apr 10, 3:33 AM CDT | Mesoscale Discussion | SPC | 57 min |
| Apr 10, 4:37 AM CDT | Severe Thunderstorm Warning | OHX | 38 min |
| Apr 10, 8:22 AM CDT | Mesoscale Discussion | SPC | 83 min |
| Apr 10, 8:53 AM CDT | Tornado Watch | SPC | 7 hr |
| Apr 10, 11:14 AM CDT | Mesoscale Discussion | SPC | 76 min |
| Apr 10, 11:23 AM CDT | Tornado Watch | SPC | 8 hr |
| Apr 10, 11:37 AM CDT | Severe Thunderstorm Warning | OHX | 38 min |
| Apr 10, 12:00 PM CDT | Severe Thunderstorm Warning | OHX | 45 min |
| Apr 10, 12:07 PM CDT | Tornado Warning | OHX | 38 min |
| Apr 10, 12:14 PM CDT | Tornado Warning | OHX | 31 min |
| Apr 10, 12:18 PM CDT | Severe Thunderstorm Warning | OHX | 42 min |
| Apr 10, 12:23 PM CDT | Severe Thunderstorm Warning | OHX | 52 min |
| Apr 10, 12:43 PM CDT | Tornado Warning | OHX | 32 min |
| Apr 10, 12:50 PM CDT | Tornado Warning | OHX | 25 min |
| Apr 10, 12:58 PM CDT | Mesoscale Discussion | SPC | 92 min |
| Apr 13, 12:09 PM CDT | Mesoscale Discussion | SPC | 66 min |
| Apr 13, 12:58 PM CDT | Tornado Watch | SPC | 7 hr |
| Apr 19, 4:30 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| May 1, 12:24 AM CDT | Severe Thunderstorm Warning | OHX | 36 min |
| May 1, 1:18 PM CDT | Mesoscale Discussion | SPC | 87 min |
| May 1, 4:27 PM CDT | Flash Flood Watch | OHX | 8 hr |
| May 1, 5:03 PM CDT | Flash Flood Warning | OHX | 5 hr |
| May 1, 5:27 PM CDT | Flash Flood Warning | OHX | 5 hr |
| May 1, 6:21 PM CDT | Flash Flood Warning | OHX | 3 hr |
| May 2, 3:17 AM CDT | Flood Watch | OHX | 48 hr |
| May 2, 12:01 PM CDT | River Flood Advisory | OHX | 9 hr |
| May 5, 3:10 PM CDT | Flood Watch | OHX | 23 hr |
| May 8, 4:18 AM CDT | Severe Thunderstorm Warning | OHX | 27 min |
| May 8, 4:29 AM CDT | Severe Thunderstorm Watch | SPC | 3 hr |
| May 8, 8:37 AM CDT | Mesoscale Discussion | SPC | 53 min |
| May 8, 9:21 AM CDT | Tornado Watch | SPC | 7 hr |
| May 8, 11:30 AM CDT | Flash Flood Watch | OHX | 37 hr |
| May 8, 3:24 PM CDT | Mesoscale Discussion | SPC | 66 min |
| May 8, 3:42 PM CDT | Tornado Watch | SPC | 7 hr |
| May 8, 7:30 PM CDT | Mesoscale Discussion | SPC | 90 min |
| May 9, 2:22 AM CDT | Mesoscale Discussion | SPC | 53 min |
| May 15, 12:04 PM CDT | Severe Thunderstorm Warning | OHX | 26 min |
| May 15, 12:57 PM CDT | Mesoscale Discussion | SPC | 63 min |
| May 15, 1:08 PM CDT | Severe Thunderstorm Warning | OHX | 37 min |
| May 16, 11:27 AM CDT | Flash Flood Watch | OHX | 10 hr |
| May 16, 1:04 PM CDT | Mesoscale Discussion | SPC | 56 min |
| May 16, 1:49 PM CDT | Severe Thunderstorm Warning | OHX | 56 min |
| May 18, 2:35 PM CDT | Frost Advisory | OHX | 18 hr |
| May 27, 12:37 PM CDT | Severe Thunderstorm Warning | OHX | 23 min |
| May 28, 12:28 PM CDT | Mesoscale Discussion | SPC | 62 min |
| Jun 2, 1:52 PM CDT | Severe Thunderstorm Warning | OHX | 23 min |
| Jun 2, 1:55 PM CDT | Severe Thunderstorm Warning | OHX | 35 min |
| Jun 11, 7:54 AM CDT | Mesoscale Discussion | SPC | 66 min |
| Jun 11, 8:18 AM CDT | Severe Thunderstorm Warning | OHX | 27 min |
| Jun 11, 8:40 AM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jun 11, 8:42 AM CDT | Severe Thunderstorm Warning | OHX | 33 min |
| Jun 11, 9:10 AM CDT | Severe Thunderstorm Warning | OHX | 35 min |
| Jun 11, 7:47 PM CDT | Mesoscale Discussion | SPC | 58 min |
| Jun 11, 8:18 PM CDT | Tornado Watch | SPC | 4 hr |
| Jun 11, 10:29 PM CDT | Mesoscale Discussion | SPC | 61 min |
| Jun 12, 5:54 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jun 15, 10:34 AM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 15, 1:56 PM CDT | Mesoscale Discussion | SPC | 64 min |
| Jun 16, 1:10 PM CDT | Mesoscale Discussion | SPC | 35 min |
| Jun 16, 1:42 PM CDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jun 16, 1:50 PM CDT | Severe Thunderstorm Warning | OHX | 40 min |
| Jun 16, 2:14 PM CDT | Severe Thunderstorm Warning | OHX | 46 min |
| Jun 16, 2:17 PM CDT | Severe Thunderstorm Warning | OHX | 43 min |
| Jun 16, 2:46 PM CDT | Severe Thunderstorm Warning | OHX | 44 min |
| Jun 17, 10:29 AM CDT | Mesoscale Discussion | SPC | 61 min |
| Jun 17, 3:36 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jun 17, 4:38 PM CDT | Severe Thunderstorm Warning | OHX | 37 min |
| Jun 17, 4:45 PM CDT | Severe Thunderstorm Warning | OHX | 30 min |
| Jun 17, 5:16 PM CDT | Severe Thunderstorm Warning | OHX | 14 min |
| Jun 17, 8:17 PM CDT | Severe Thunderstorm Warning | OHX | 28 min |
| Jun 22, 5:25 PM CDT | Severe Thunderstorm Warning | OHX | 35 min |
| Jun 22, 5:56 PM CDT | Severe Thunderstorm Warning | OHX | 34 min |
| Jun 22, 9:03 PM CDT | Severe Thunderstorm Warning | OHX | 27 min |
| Jun 22, 9:13 PM CDT | Severe Thunderstorm Warning | OHX | 32 min |
| Jun 30, 11:35 PM CDT | Mesoscale Discussion | SPC | 85 min |
| Jul 4, 5:56 PM CDT | Severe Thunderstorm Watch | SPC | 3 hr |
| Jul 4, 8:02 PM CDT | Mesoscale Discussion | SPC | 28 min |
| Jul 5, 1:21 PM CDT | Mesoscale Discussion | SPC | 54 min |
| Jul 5, 3:10 PM CDT | Severe Thunderstorm Warning | OHX | 35 min |
| Jul 12, 4:23 PM CDT | Severe Thunderstorm Warning | OHX | 37 min |
| Jul 12, 6:50 PM CDT | Severe Thunderstorm Warning | OHX | 40 min |
| Jul 12, 8:07 PM CDT | Severe Thunderstorm Warning | OHX | 38 min |
| Jul 15, 1:36 PM CDT | Mesoscale Discussion | SPC | 84 min |
| Jul 15, 4:18 PM CDT | Severe Thunderstorm Warning | OHX | 42 min |
| Jul 15, 7:49 PM CDT | Mesoscale Discussion | SPC | 56 min |
| Jul 30, 2:48 PM CDT | Flood Watch | OHX | 13 hr |
| Jul 30, 4:10 PM CDT | Tornado Watch | SPC | 6 hr |
| Jul 30, 5:01 PM CDT | Mesoscale Discussion | SPC | 59 min |
| Jul 30, 6:29 PM CDT | Mesoscale Discussion | SPC | 61 min |
| Aug 1, 2:35 PM CDT | Flash Flood Watch | OHX | 13 hr |
| Aug 4, 6:21 PM CDT | Mesoscale Discussion | SPC | 114 min |
| Aug 4, 6:34 PM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Aug 4, 8:21 PM CDT | Severe Thunderstorm Warning | OHX | 39 min |
| Aug 4, 8:35 PM CDT | Mesoscale Discussion | SPC | 85 min |
| Aug 4, 8:42 PM CDT | Severe Thunderstorm Warning | OHX | 33 min |
| Aug 12, 3:47 AM CDT | Dense Fog Advisory | OHX | 3 hr |
| Sep 3, 5:45 AM CDT | Areal Flood Advisory | OHX | 3 hr |
| Sep 16, 10:22 AM CDT | Areal Flood Advisory | OHX | 6 hr |
| Sep 16, 3:36 PM CDT | Flood Watch | OHX | 51 hr |
| Sep 19, 2:39 AM CDT | Flood Watch | OHX | 45 hr |
| Sep 23, 3:20 AM CDT | Flash Flood Watch | OHX | 16 hr |
| Sep 25, 4:06 AM CDT | Flash Flood Watch | OHX | 36 hr |
| Oct 9, 12:08 PM CDT | Mesoscale Discussion | SPC | 67 min |
| Oct 9, 12:24 PM CDT | Tornado Watch | SPC | 7 hr |
| Oct 9, 12:47 PM CDT | Severe Thunderstorm Warning | OHX | 28 min |
| Oct 9, 1:41 PM CDT | Severe Thunderstorm Warning | OHX | 34 min |
| Oct 17, 3:59 AM CDT | Frost Advisory | OHX | 28 hr |
| Oct 17, 3:59 AM CDT | Freeze Watch | OHX | 24 hr |
| Oct 18, 3:33 AM CDT | Freeze Warning | OHX | 29 hr |
| Oct 24, 11:01 AM CDT | Frost Advisory | OHX | 21 hr |
| Oct 29, 4:05 AM CDT | Dense Fog Advisory | OHX | 4 hr |
| Nov 1, 3:04 AM CST | Frost Advisory | OHX | 28 hr |
| Nov 2, 3:40 AM CST | Freeze Watch | OHX | 31 hr |
| Nov 3, 10:43 AM CST | Freeze Warning | OHX | 19 hr |
| Nov 4, 3:32 PM CST | Freeze Watch | OHX | 24 hr |
| Nov 5, 3:16 PM CST | Freeze Warning | OHX | 16 hr |
| Nov 7, 12:30 PM CST | Red Flag Warning | OHX | 6 hr |
| Nov 19, 2:56 PM CST | Frost Advisory | OHX | 16 hr |
| Nov 25, 3:39 PM CST | Freeze Watch | OHX | 23 hr |
| Nov 26, 3:06 PM CST | Freeze Warning | OHX | 17 hr |
| Dec 8, 11:47 AM CST | Areal Flood Advisory | OHX | 12 hr |
| Dec 8, 11:47 AM CST | Wind Advisory | OHX | 26 hr |
| Dec 21, 10:39 PM CST | Freezing Fog Advisory | OHX | 10 hr |
| Dec 23, 4:28 AM CST | Wind Advisory | OHX | 47 hr |
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
| Product | Alerts |
|---|---|
| Severe storms | |
| Severe Thunderstorm Warning | 50 |
| Tornado Warning | 7 |
| Severe Thunderstorm Watch | 11 |
| Tornado Watch | 14 |
| Mesoscale Discussion | 34 |
| Flooding | |
| Areal Flood Warning | 1 |
| Flash Flood Warning | 5 |
| Flash Flood Watch | 6 |
| Flood Watch | 7 |
| Areal Flood Advisory | 6 |
| River Flood Advisory | 1 |
| Winter | |
| Winter Weather Advisory | 3 |
| Cold | |
| Freeze Warning | 6 |
| Freeze Watch | 6 |
| Frost Advisory | 5 |
| Wind and dust | |
| Wind Advisory | 3 |
| Fire | |
| Red Flag Warning | 1 |
| Fog and smoke | |
| Dense Fog Advisory | 3 |
| Freezing Fog Advisory | 1 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20082010
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.