Alert archive / Pennsylvania / Delaware County
Weather alerts in Delaware County, Pennsylvania, 2009
164 weather alerts in 2009, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Delaware County and its neighbors
Each county as a circle sized by its count in 2009. Tap one for its archive.
- Alerts
- 164
- Warnings
- 43
- Watches
- 31
- Advisories
- 46
- Busiest month
- August29 alerts
- Busiest day
- August 9, 20098 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Delaware County, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 20 | 16 | 20% | 11 | 73% | 19 min |
| Flash flood warnings | 5 | 3 | 40% | 5 | 60% | 83 min |
Each office's whole area, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Philadelphia/Mount Holly: tornado warnings | 13 | 1 | 92% | 2 | 50% | 38 min |
| NWS Philadelphia/Mount Holly: severe thunderstorm warnings | 235 | 113 | 52% | 260 | 82% | 26 min |
| NWS Philadelphia/Mount Holly: flash flood warnings | 67 | 20 | 70% | 69 | 62% | 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, Eastern Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 6, 4:39 AM EST | Winter Weather Advisory | PHI | 23 hr |
| Jan 7, 8:21 AM EST | Areal Flood Advisory | PHI | 8 hr |
| Jan 9, 3:27 PM EST | Winter Weather Advisory | PHI | 37 hr |
| Jan 26, 2:42 AM EST | Winter Storm Watch | PHI | 25 hr |
| Jan 27, 3:18 AM EST | Winter Storm Warning | PHI | 40 hr |
| Jan 28, 12:31 AM EST | Mesoscale Discussion | SPC | 5 hr |
| Jan 28, 10:01 AM EST | Dense Fog Advisory | PHI | 7 hr |
| Feb 2, 2:53 PM EST | Winter Storm Watch | PHI | 13 hr |
| Feb 2, 2:53 PM EST | Winter Weather Advisory | PHI | 37 hr |
| Feb 3, 9:40 PM EST | Winter Storm Warning | PHI | 6 hr |
| Feb 11, 2:50 PM EST | Wind Advisory | PHI | 13 hr |
| Feb 11, 10:14 PM EST | Mesoscale Discussion | SPC | 61 min |
| Feb 12, 3:30 AM EST | High Wind Warning | PHI | 16 hr |
| Feb 12, 6:51 PM EST | Wind Advisory | PHI | 5 hr |
| Feb 28, 4:10 AM EST | Winter Storm Watch | PHI | 23 hr |
| Mar 1, 3:30 AM EST | Winter Storm Warning | PHI | 37 hr |
| Mar 1, 9:09 PM EST | Mesoscale Discussion | SPC | 4 hr |
| Mar 2, 5:38 AM EST | Mesoscale Discussion | SPC | 3 hr |
| Mar 9, 4:12 AM EDT | Wind Advisory | PHI | 12 hr |
| Mar 23, 4:23 AM EDT | Red Flag Warning | PHI | 19 hr |
| Mar 29, 1:49 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Mar 29, 5:53 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Mar 29, 6:11 PM EDT | Severe Thunderstorm Warning | PHI | 64 min |
| Apr 2, 5:13 AM EDT | Dense Fog Advisory | PHI | 4 hr |
| Apr 3, 3:08 PM EDT | Wind Advisory | PHI | 29 hr |
| Apr 5, 3:06 PM EDT | Flood Watch | PHI | 22 hr |
| Apr 16, 3:01 PM EDT | Frost Advisory | PHI | 17 hr |
| Apr 19, 2:36 PM EDT | Flood Watch | PHI | 22 hr |
| Apr 23, 4:00 AM EDT | Frost Advisory | PHI | 28 hr |
| Apr 28, 10:34 AM EDT | Red Flag Warning | PHI | 9 hr |
| May 6, 9:01 PM EDT | Flood Watch | PHI | 19 hr |
| May 7, 1:51 AM EDT | Flash Flood Warning | PHI | 5 hr |
| May 7, 2:34 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| May 16, 3:41 AM EDT | Dense Fog Advisory | PHI | 5 hr |
| May 16, 6:29 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 24, 7:11 PM EDT | Mesoscale Discussion | SPC | 64 min |
| May 24, 8:04 PM EDT | Severe Thunderstorm Warning | PHI | 56 min |
| May 29, 12:20 PM EDT | Mesoscale Discussion | SPC | 55 min |
| May 29, 1:26 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| May 29, 4:30 PM EDT | Mesoscale Discussion | SPC | 60 min |
| May 29, 5:10 PM EDT | Severe Thunderstorm Warning | PHI | 42 min |
| May 29, 6:20 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Jun 2, 1:31 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Jun 2, 1:58 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jun 2, 2:53 PM EDT | Severe Thunderstorm Warning | PHI | 67 min |
| Jun 4, 2:54 PM EDT | Flood Watch | PHI | 29 hr |
| Jun 9, 6:01 AM EDT | Mesoscale Discussion | SPC | 59 min |
| Jun 9, 7:20 AM EDT | Severe Thunderstorm Warning | PHI | 55 min |
| Jun 9, 8:00 AM EDT | Severe Thunderstorm Warning | PHI | 60 min |
| Jun 9, 8:20 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jun 9, 1:49 PM EDT | Flash Flood Watch | PHI | 5 hr |
| Jun 11, 4:10 PM EDT | Coastal Flood Statement | PHI | 12 hr |
| Jun 11, 10:01 PM EDT | Mesoscale Discussion | SPC | 59 min |
| Jun 15, 5:55 PM EDT | Severe Thunderstorm Warning | PHI | 65 min |
| Jun 15, 6:37 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Jun 17, 1:23 PM EDT | Coastal Flood Advisory | PHI | 6 hr |
| Jun 18, 11:40 AM EDT | Mesoscale Discussion | SPC | 95 min |
| Jun 18, 2:53 PM EDT | Coastal Flood Advisory | PHI | 9 hr |
| Jun 21, 3:28 PM EDT | Coastal Flood Advisory | PHI | 38 hr |
| Jun 23, 5:04 AM EDT | Coastal Flood Advisory | PHI | 24 hr |
| Jun 24, 6:00 AM EDT | Coastal Flood Advisory | PHI | 24 hr |
| Jun 26, 2:19 PM EDT | Mesoscale Discussion | SPC | 56 min |
| Jun 26, 2:42 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 26, 7:15 PM EDT | Severe Thunderstorm Warning | PHI | 60 min |
| Jun 26, 7:33 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jun 26, 9:11 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Jun 30, 11:37 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 30, 2:18 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jul 1, 12:03 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Jul 16, 4:04 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 17, 6:18 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jul 17, 7:22 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Jul 17, 7:33 PM EDT | Areal Flood Advisory | PHI | 86 min |
| Jul 24, 3:34 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 24, 6:28 PM EDT | Severe Thunderstorm Warning | PHI | 62 min |
| Jul 24, 7:11 PM EDT | Severe Thunderstorm Warning | PHI | 46 min |
| Jul 26, 3:07 AM EDT | Flash Flood Watch | PHI | 20 hr |
| Jul 26, 1:40 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 26, 3:14 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 26, 3:51 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 26, 6:37 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Jul 29, 10:15 AM EDT | Flash Flood Watch | PHI | 17 hr |
| Jul 29, 12:49 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 29, 5:05 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Jul 29, 5:55 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Jul 29, 7:14 PM EDT | Mesoscale Discussion | SPC | 61 min |
| Jul 29, 8:36 PM EDT | Areal Flood Advisory | PHI | 101 min |
| Jul 30, 3:30 PM EDT | Flash Flood Watch | PHI | 27 hr |
| Jul 31, 12:06 PM EDT | Mesoscale Discussion | SPC | 84 min |
| Jul 31, 1:18 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 31, 3:05 PM EDT | Mesoscale Discussion | SPC | 85 min |
| Jul 31, 3:36 PM EDT | Severe Thunderstorm Warning | PHI | 54 min |
| Jul 31, 4:03 PM EDT | Severe Thunderstorm Warning | PHI | 57 min |
| Jul 31, 4:08 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Jul 31, 4:31 PM EDT | Severe Thunderstorm Warning | PHI | 59 min |
| Aug 2, 2:19 AM EDT | Flash Flood Watch | PHI | 13 hr |
| Aug 2, 10:01 AM EDT | Mesoscale Discussion | SPC | 119 min |
| Aug 2, 10:08 AM EDT | Flash Flood Warning | PHI | 9 hr |
| Aug 2, 10:24 AM EDT | Severe Thunderstorm Warning | PHI | 66 min |
| Aug 2, 10:53 AM EDT | Severe Thunderstorm Warning | PHI | 67 min |
| Aug 8, 1:35 PM EDT | Excessive Heat Watch | PHI | 24 hr |
| Aug 9, 9:23 AM EDT | Areal Flood Advisory | PHI | 83 min |
| Aug 9, 11:57 AM EDT | Flash Flood Watch | PHI | 11 hr |
| Aug 9, 1:56 PM EDT | Excessive Heat Warning | PHI | 30 hr |
| Aug 9, 2:45 PM EDT | Mesoscale Discussion | SPC | 60 min |
| Aug 9, 3:18 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 9, 6:03 PM EDT | Areal Flood Advisory | PHI | 117 min |
| Aug 9, 6:10 PM EDT | Severe Thunderstorm Warning | PHI | 80 min |
| Aug 9, 7:11 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 12, 1:01 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Aug 13, 3:36 AM EDT | Flood Watch | PHI | 36 min |
| Aug 13, 4:12 AM EDT | Flash Flood Watch | PHI | 15 hr |
| Aug 13, 9:13 AM EDT | River Flood Warning | PHI | 5 hr |
| Aug 18, 7:22 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Aug 18, 7:37 PM EDT | Severe Thunderstorm Warning | PHI | 68 min |
| Aug 19, 6:05 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Aug 21, 10:01 AM EDT | Mesoscale Discussion | SPC | 119 min |
| Aug 21, 11:28 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 21, 2:47 PM EDT | Flash Flood Watch | PHI | 35 hr |
| Aug 22, 7:00 PM EDT | Flash Flood Warning | PHI | 4 hr |
| Aug 28, 12:24 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 28, 2:52 PM EDT | Flash Flood Watch | PHI | 14 hr |
| Aug 28, 3:13 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Aug 29, 10:33 PM EDT | Areal Flood Warning | PHI | 2 hr |
| Sep 10, 2:50 PM EDT | Flash Flood Watch | PHI | 25 hr |
| Sep 11, 8:41 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Sep 15, 2:52 PM EDT | Coastal Flood Advisory | PHI | 59 hr |
| Oct 6, 3:19 PM EDT | Wind Advisory | PHI | 29 hr |
| Oct 16, 4:09 PM EDT | Coastal Flood Advisory | PHI | 36 hr |
| Oct 18, 9:18 AM EDT | Coastal Flood Advisory | PHI | 30 hr |
| Oct 18, 2:04 PM EDT | Frost Advisory | PHI | 19 hr |
| Oct 19, 1:12 PM EDT | Frost Advisory | PHI | 18 hr |
| Oct 24, 12:19 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Oct 24, 4:49 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Oct 24, 5:41 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Oct 24, 9:26 PM EDT | Areal Flood Warning | PHI | 5 hr |
| Oct 30, 3:05 AM EDT | Coastal Flood Statement | PHI | 10 hr |
| Oct 31, 3:02 AM EDT | Coastal Flood Advisory | PHI | 12 hr |
| Nov 2, 2:55 PM EST | Freeze Watch | PHI | 11 hr |
| Nov 2, 11:33 PM EST | Coastal Flood Advisory | PHI | 15 hr |
| Nov 3, 2:09 AM EST | Frost Advisory | PHI | 30 hr |
| Nov 12, 3:00 AM EST | Coastal Flood Advisory | PHI | 3 days |
| Nov 27, 3:16 PM EST | Wind Advisory | PHI | 24 hr |
| Dec 3, 8:49 AM EST | Coastal Flood Advisory | PHI | 4 hr |
| Dec 5, 3:25 AM EST | Winter Weather Advisory | PHI | 19 hr |
| Dec 8, 2:40 PM EST | Flash Flood Watch | PHI | 21 hr |
| Dec 9, 6:53 AM EST | Areal Flood Warning | PHI | 8 hr |
| Dec 9, 8:25 AM EST | River Flood Warning | PHI | 5 hr |
| Dec 9, 10:40 AM EST | River Flood Warning | PHI | 13 hr |
| Dec 9, 12:00 PM EST | Wind Advisory | PHI | 33 hr |
| Dec 9, 2:26 PM EST | Coastal Flood Advisory | PHI | 7 hr |
| Dec 9, 2:55 PM EST | Areal Flood Warning | PHI | 7 hr |
| Dec 17, 3:30 PM EST | Winter Storm Watch | PHI | 22 hr |
| Dec 18, 4:40 AM EST | Winter Storm Warning | PHI | 46 hr |
| Dec 19, 12:34 AM EST | Mesoscale Discussion | SPC | 5 hr |
| Dec 19, 6:57 AM EST | Mesoscale Discussion | SPC | 6 hr |
| Dec 19, 12:27 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Dec 19, 7:25 PM EST | Mesoscale Discussion | SPC | 5 hr |
| Dec 26, 7:42 AM EST | Coastal Flood Advisory | PHI | 15 hr |
| Dec 26, 10:28 AM EST | Areal Flood Warning | PHI | 20 hr |
| Dec 26, 12:34 PM EST | River Flood Warning | PHI | 9 hr |
| Dec 26, 2:45 PM EST | River Flood Warning | PHI | 17 hr |
| Dec 28, 1:42 PM EST | Wind Advisory | PHI | 27 hr |
| Dec 31, 3:22 AM EST | Winter Weather Advisory | PHI | 8 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 | 20 |
| Severe Thunderstorm Watch | 9 |
| Mesoscale Discussion | 42 |
| Flooding | |
| Areal Flood Warning | 5 |
| Flash Flood Warning | 5 |
| River Flood Warning | 5 |
| Flash Flood Watch | 11 |
| Flood Watch | 5 |
| Areal Flood Advisory | 11 |
| Winter | |
| Winter Storm Warning | 4 |
| Winter Storm Watch | 4 |
| Winter Weather Advisory | 5 |
| Heat | |
| Excessive Heat Warning | 1 |
| Excessive Heat Watch | 1 |
| Cold | |
| Freeze Watch | 1 |
| Frost Advisory | 5 |
| Wind and dust | |
| High Wind Warning | 1 |
| Wind Advisory | 8 |
| Fire | |
| Red Flag Warning | 2 |
| Fog and smoke | |
| Dense Fog Advisory | 3 |
| Coast and beach | |
| Coastal Flood Advisory | 14 |
| Coastal Flood Statement | 2 |
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.