Alert archive / California / Alameda County
Weather alerts in Alameda County, California, 2009
39 weather alerts in 2009, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Alameda County and its neighbors
Each county as a circle sized by its count in 2009. Tap one for its archive.
- Alerts
- 39
- Warnings
- 4
- Watches
- 5
- Advisories
- 30
- Busiest month
- October11 alerts
- Busiest day
- February 16, 20092 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Alameda County, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 1 | 0 | 100% | 0 | ||
| Flash flood warnings | 0 | 0 |
Each office's whole area, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS San Francisco Bay Area, CA: severe thunderstorm warnings | 2 | 0 | 100% | 1 | 0% | |
| NWS San Francisco Bay Area, CA: flash flood warnings | 10 | 0 | 100% | 1 | 0% |
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, Pacific Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Dec 31, 4:01 PM PST | Dense Fog Advisory | MTR | 17 hr |
| Jan 3, 11:51 PM PST | Frost Advisory | MTR | 8 hr |
| Jan 7, 3:08 AM PST | Dense Fog Advisory | MTR | 6 hr |
| Jan 9, 3:23 AM PST | Dense Fog Advisory | MTR | 7 hr |
| Feb 13, 2:19 PM PST | High Wind Watch | MTR | 12 hr |
| Feb 14, 2:48 AM PST | Wind Advisory | MTR | 45 hr |
| Feb 15, 7:01 PM PST | Areal Flood Advisory | MTR | 5 hr |
| Feb 16, 7:54 AM PST | Areal Flood Advisory | MTR | 97 min |
| Feb 17, 7:18 AM PST | Areal Flood Advisory | MTR | 3 hr |
| Feb 19, 5:51 AM PST | Dense Fog Advisory | MTR | 3 hr |
| Feb 22, 9:29 PM PST | Areal Flood Advisory | MTR | 8 hr |
| Mar 1, 10:20 PM PST | Wind Advisory | MTR | 29 hr |
| Apr 2, 6:12 PM PDT | Wind Advisory | MTR | 3 hr |
| Apr 3, 3:24 PM PDT | Wind Advisory | MTR | 5 hr |
| Apr 13, 2:35 PM PDT | Wind Advisory | MTR | 32 hr |
| Apr 19, 4:54 PM PDT | Heat Advisory | MTR | 27 hr |
| May 15, 11:23 AM PDT | Heat Advisory | MTR | 57 hr |
| Jun 3, 5:44 PM PDT | Severe Thunderstorm Warning | MTR | 31 min |
| Jun 25, 2:27 PM PDT | Heat Advisory | MTR | 3 days |
| Aug 28, 7:00 PM PDT | Flood Watch | MTR | 45 hr |
| Sep 19, 1:55 PM PDT | Excessive Heat Watch | MTR | 24 hr |
| Sep 20, 1:31 PM PDT | Heat Advisory | MTR | 44 hr |
| Oct 2, 2:32 PM PDT | Wind Advisory | MTR | 36 hr |
| Oct 11, 2:46 PM PDT | High Wind Watch | MTR | 11 hr |
| Oct 12, 2:09 AM PDT | High Wind Warning | MTR | 45 hr |
| Oct 12, 2:09 AM PDT | Wind Advisory | MTR | 45 hr |
| Oct 13, 9:54 AM PDT | Areal Flood Advisory | MTR | 3 hr |
| Oct 13, 2:48 PM PDT | Areal Flood Advisory | MTR | 4 hr |
| Oct 13, 6:41 PM PDT | Areal Flood Advisory | MTR | 4 hr |
| Oct 18, 8:20 AM PDT | Dense Fog Advisory | MTR | 2 hr |
| Oct 19, 3:29 PM PDT | Areal Flood Advisory | MTR | 100 min |
| Oct 19, 4:15 PM PDT | Areal Flood Advisory | MTR | 91 min |
| Oct 26, 3:12 AM PDT | Wind Advisory | MTR | 47 hr |
| Nov 15, 3:42 AM PST | Frost Advisory | MTR | 28 hr |
| Dec 5, 2:01 PM PST | Freeze Watch | MTR | 38 hr |
| Dec 7, 4:09 AM PST | Frost Advisory | MTR | 29 hr |
| Dec 7, 4:09 AM PST | Freeze Warning | MTR | 29 hr |
| Dec 8, 9:47 AM PST | Frost Advisory | MTR | 23 hr |
| Dec 8, 9:47 AM PST | Freeze Warning | MTR | 23 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 | 1 |
| Flooding | |
| Flood Watch | 1 |
| Areal Flood Advisory | 9 |
| Heat | |
| Excessive Heat Watch | 1 |
| Heat Advisory | 4 |
| Cold | |
| Freeze Warning | 2 |
| Freeze Watch | 1 |
| Frost Advisory | 4 |
| Wind and dust | |
| High Wind Warning | 1 |
| High Wind Watch | 2 |
| Wind Advisory | 8 |
| Fog and smoke | |
| Dense Fog Advisory | 5 |
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.