Alert archive / Pennsylvania / Chester County
Weather alerts in Chester County, Pennsylvania, 2008
99 weather alerts in 2008, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Chester County and its neighbors
Each county as a circle sized by its count in 2008. Tap one for its archive.
- Alerts
- 99
- Warnings
- 40
- Watches
- 16
- Advisories
- 10
- Busiest month
- June28 alerts
- Busiest day
- August 10, 200813 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Chester County, 2008
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 27 | 13 | 52% | 13 | 77% | 37 min |
| Flash flood warnings | 7 | 1 | 86% | 0 |
Each office's whole area, 2008
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Philadelphia/Mount Holly: tornado warnings | 9 | 0 | 100% | 1 | 0% | |
| NWS Philadelphia/Mount Holly: severe thunderstorm warnings | 273 | 120 | 56% | 264 | 79% | 26 min |
| NWS Philadelphia/Mount Holly: flash flood warnings | 37 | 13 | 65% | 21 | 71% | 58 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, Eastern Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 17, 12:53 PM EST | Mesoscale Discussion | SPC | 4 hr |
| Feb 6, 9:41 PM EST | Mesoscale Discussion | SPC | 64 min |
| Feb 12, 4:15 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Feb 13, 9:49 PM EST | River Flood Warning | PHI | 4 hr |
| Feb 22, 12:40 AM EST | Mesoscale Discussion | SPC | 6 hr |
| Feb 22, 7:01 AM EST | Mesoscale Discussion | SPC | 6 hr |
| Mar 5, 12:23 AM EST | Mesoscale Discussion | SPC | 67 min |
| Mar 5, 1:04 AM EST | Severe Thunderstorm Watch | SPC | 3 hr |
| Mar 8, 12:03 PM EST | Flash Flood Warning | PHI | 4 hr |
| Mar 20, 1:17 AM EDT | Flash Flood Warning | PHI | 118 min |
| Apr 28, 5:22 PM EDT | Areal Flood Advisory | PHI | 113 min |
| May 27, 7:14 PM EDT | Mesoscale Discussion | SPC | 61 min |
| May 31, 8:54 AM EDT | Mesoscale Discussion | SPC | 96 min |
| May 31, 10:20 AM EDT | Tornado Watch | SPC | 7 hr |
| May 31, 10:25 AM EDT | Tornado Watch | SPC | 7 hr |
| Jun 4, 2:53 PM EDT | Tornado Watch | SPC | 5 hr |
| Jun 8, 11:56 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 10, 4:52 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Jun 10, 5:47 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 10, 6:51 PM EDT | Mesoscale Discussion | SPC | 54 min |
| Jun 10, 7:02 PM EDT | Severe Thunderstorm Warning | PHI | 58 min |
| Jun 10, 7:36 PM EDT | Severe Thunderstorm Warning | PHI | 54 min |
| Jun 14, 6:15 PM EDT | Severe Thunderstorm Warning | PHI | 75 min |
| Jun 14, 6:28 PM EDT | Flash Flood Warning | PHI | 60 min |
| Jun 14, 7:05 PM EDT | Severe Thunderstorm Warning | PHI | 70 min |
| Jun 14, 7:42 PM EDT | Severe Thunderstorm Warning | PHI | 63 min |
| Jun 16, 12:54 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 16, 1:21 PM EDT | Severe Thunderstorm Watch | SPC | 10 hr |
| Jun 18, 4:57 PM EDT | Severe Thunderstorm Warning | PHI | 42 min |
| Jun 23, 3:30 AM EDT | Mesoscale Discussion | SPC | 90 min |
| Jun 23, 10:54 PM EDT | Severe Thunderstorm Warning | PHI | 43 min |
| Jun 23, 11:20 PM EDT | Severe Thunderstorm Warning | PHI | 55 min |
| Jun 27, 11:37 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 27, 12:40 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 27, 4:12 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Jun 28, 9:35 PM EDT | Severe Thunderstorm Warning | PHI | 70 min |
| Jun 29, 4:11 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 29, 7:13 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Jun 29, 8:09 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 29, 9:30 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 29, 11:58 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Jun 30, 12:15 AM EDT | Mesoscale Discussion | SPC | 90 min |
| Jun 30, 7:52 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Jul 1, 12:19 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 20, 8:17 PM EDT | Severe Thunderstorm Warning | PHI | 58 min |
| Jul 20, 9:22 PM EDT | Severe Thunderstorm Warning | PHI | 23 min |
| Jul 22, 2:15 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 23, 4:23 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 23, 2:34 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 23, 3:58 PM EDT | Severe Thunderstorm Warning | PHI | 62 min |
| Jul 23, 4:27 PM EDT | Severe Thunderstorm Warning | PHI | 38 min |
| Jul 23, 8:24 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 23, 9:26 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Jul 23, 10:49 PM EDT | Areal Flood Advisory | PHI | 107 min |
| Jul 27, 11:03 AM EDT | Mesoscale Discussion | SPC | 57 min |
| Jul 27, 11:26 AM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 27, 12:07 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Jul 27, 12:19 PM EDT | Severe Thunderstorm Warning | PHI | 56 min |
| Jul 27, 12:25 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 27, 12:38 PM EDT | Severe Thunderstorm Warning | PHI | 67 min |
| Jul 27, 12:50 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 27, 12:57 PM EDT | Severe Thunderstorm Warning | PHI | 63 min |
| Jul 27, 1:34 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Jul 27, 5:04 PM EDT | Severe Thunderstorm Warning | PHI | 56 min |
| Jul 27, 6:44 PM EDT | Areal Flood Advisory | PHI | 72 min |
| Jul 30, 2:23 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Jul 30, 4:53 PM EDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Jul 30, 7:47 PM EDT | Mesoscale Discussion | SPC | 88 min |
| Aug 2, 10:39 AM EDT | Severe Thunderstorm Watch | SPC | 9 hr |
| Aug 7, 5:42 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Aug 10, 10:18 AM EDT | Severe Thunderstorm Warning | PHI | 57 min |
| Aug 10, 10:27 AM EDT | Mesoscale Discussion | SPC | 33 min |
| Aug 10, 10:46 AM EDT | Severe Thunderstorm Watch | SPC | 10 hr |
| Aug 10, 11:09 AM EDT | Severe Thunderstorm Warning | PHI | 66 min |
| Aug 10, 11:32 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 10, 12:17 PM EDT | Flash Flood Warning | PHI | 4 hr |
| Aug 10, 1:05 PM EDT | Mesoscale Discussion | SPC | 85 min |
| Aug 10, 1:10 PM EDT | Severe Thunderstorm Warning | PHI | 65 min |
| Aug 10, 1:47 PM EDT | Severe Thunderstorm Warning | PHI | 58 min |
| Aug 10, 3:05 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Aug 10, 4:45 PM EDT | Severe Thunderstorm Warning | PHI | 75 min |
| Aug 10, 5:45 PM EDT | Severe Thunderstorm Warning | PHI | 75 min |
| Aug 10, 5:59 PM EDT | Areal Flood Advisory | PHI | 2 hr |
| Aug 14, 6:15 PM EDT | Mesoscale Discussion | SPC | 60 min |
| Sep 6, 4:22 PM EDT | Areal Flood Warning | PHI | 6 hr |
| Sep 9, 8:35 AM EDT | Mesoscale Discussion | SPC | 115 min |
| Sep 9, 8:51 AM EDT | Severe Thunderstorm Warning | PHI | 39 min |
| Sep 9, 9:21 AM EDT | Severe Thunderstorm Warning | PHI | 39 min |
| Sep 9, 9:30 AM EDT | Flash Flood Warning | PHI | 3 hr |
| Sep 9, 9:33 AM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Nov 15, 12:22 PM EST | Tornado Watch | SPC | 7 hr |
| Nov 15, 4:15 PM EST | Severe Thunderstorm Warning | PHI | 60 min |
| Dec 11, 9:32 PM EST | Areal Flood Warning | PHI | 12 hr |
| Dec 11, 9:47 PM EST | Areal Flood Advisory | PHI | 6 hr |
| Dec 12, 12:55 AM EST | Areal Flood Warning | PHI | 12 hr |
| Dec 12, 3:46 AM EST | River Flood Warning | PHI | 10 hr |
| Dec 12, 11:17 AM EST | River Flood Warning | PHI | 9 hr |
| Dec 16, 11:55 PM EST | Mesoscale Discussion | SPC | 4 hr |
| Dec 20, 11:55 PM EST | Mesoscale Discussion | SPC | 4 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 | 27 |
| Severe Thunderstorm Watch | 12 |
| Tornado Watch | 4 |
| Mesoscale Discussion | 33 |
| Flooding | |
| Areal Flood Warning | 3 |
| Flash Flood Warning | 7 |
| River Flood Warning | 3 |
| Areal Flood Advisory | 10 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe 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.