Alert archive / California / Alameda County
Weather alerts in Alameda County, California, 2018
21 weather alerts in 2018, 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 2018. Tap one for its archive.
- Alerts
- 21
- Warnings
- 3
- Watches
- 4
- Advisories
- 13
- Busiest month
- December8 alerts
- Busiest day
- February 18, 20182 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, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 0 | 0 | ||||
| Flash flood warnings | 0 | 1 | 0% |
Each office's whole area, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sacramento, CA: tornado warnings | 3 | 1 | 67% | 4 | 100% | 7 min |
| NWS Sacramento, CA: severe thunderstorm warnings | 4 | 0 | 100% | 1 | 0% | |
| NWS Sacramento, CA: flash flood warnings | 5 | 0 | 100% | 0 | ||
| NWS Hanford, CA: tornado warnings | 0 | 5 | 0% | |||
| NWS Hanford, CA: severe thunderstorm warnings | 7 | 0 | 100% | 1 | 0% | |
| NWS Hanford, CA: flash flood warnings | 16 | 7 | 56% | 28 | 29% | 72 min |
| NWS Las Vegas, NV: severe thunderstorm warnings | 73 | 15 | 79% | 151 | 66% | 24 min |
| NWS Las Vegas, NV: flash flood warnings | 159 | 59 | 63% | 195 | 63% | 75 min |
| NWS Los Angeles, CA: flash flood warnings | 11 | 4 | 64% | 17 | 76% | 67 min |
| NWS Phoenix, AZ: tornado warnings | 0 | 3 | 0% | |||
| NWS Phoenix, AZ: severe thunderstorm warnings | 107 | 39 | 64% | 216 | 54% | 17 min |
| NWS Phoenix, AZ: flash flood warnings | 121 | 73 | 40% | 143 | 85% | 71 min |
| NWS San Diego, CA: tornado warnings | 0 | 1 | 0% | |||
| NWS San Diego, CA: severe thunderstorm warnings | 15 | 2 | 87% | 4 | 50% | 24 min |
| NWS San Diego, CA: flash flood warnings | 36 | 17 | 53% | 78 | 71% | 80 min |
| NWS Eureka, CA: tornado warnings | 0 | 1 | 0% | |||
| NWS Eureka, CA: flash flood warnings | 1 | 1 | 0% | 4 | 25% | 9 min |
| NWS San Francisco Bay Area, CA: flash flood warnings | 1 | 0 | 100% | 16 | 0% | |
| NWS Medford, OR: severe thunderstorm warnings | 13 | 3 | 77% | 5 | 60% | 16 min |
| NWS Reno, NV: severe thunderstorm warnings | 18 | 0 | 100% | 1 | 0% | |
| NWS Reno, NV: flash flood warnings | 19 | 5 | 74% | 13 | 46% | 57 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, Pacific Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 7, 4:33 AM PST | Wind Advisory | MTR | 46 hr |
| Jan 23, 1:35 AM PST | Tsunami Watch | AAQ | 3 hr |
| Feb 17, 7:16 PM PST | Freeze Watch | MTR | 14 hr |
| Feb 18, 9:13 AM PST | Freeze Warning | MTR | 48 hr |
| Feb 18, 4:44 PM PST | Frost Advisory | MTR | 40 hr |
| Feb 28, 4:32 AM PST | Wind Advisory | MTR | 41 hr |
| Apr 16, 10:19 AM PDT | Special Weather Statement | MTR | 26 min |
| Jun 21, 11:54 AM PDT | Heat Advisory | MTR | 56 hr |
| Oct 5, 12:01 PM PDT | Fire Weather Watch | MTR | 22 hr |
| Oct 6, 10:25 AM PDT | Red Flag Warning | MTR | 55 hr |
| Nov 27, 12:29 PM PST | High Wind Watch | MTR | 24 hr |
| Nov 28, 12:12 PM PST | Wind Advisory | MTR | 25 hr |
| Nov 28, 10:36 PM PST | Areal Flood Advisory | MTR | 54 min |
| Dec 2, 4:50 PM PST | Freeze Warning | MTR | 11 hr |
| Dec 8, 9:27 PM PST | Dense Fog Advisory | MTR | 14 hr |
| Dec 11, 2:25 AM PST | Dense Fog Advisory | MTR | 8 hr |
| Dec 20, 4:30 AM PST | Dense Fog Advisory | MTR | 6 hr |
| Dec 21, 10:33 AM PST | Coastal Flood Advisory | MTR | 25 hr |
| Dec 22, 1:09 PM PST | Coastal Flood Advisory | MTR | 24 hr |
| Dec 23, 1:42 PM PST | Coastal Flood Advisory | MTR | 24 hr |
| Dec 30, 1:52 AM PST | Wind Advisory | MTR | 56 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 | |
| Special Weather Statement | 1 |
| Flooding | |
| Areal Flood Advisory | 1 |
| Heat | |
| Heat Advisory | 1 |
| Cold | |
| Freeze Warning | 2 |
| Freeze Watch | 1 |
| Frost Advisory | 1 |
| Wind and dust | |
| High Wind Watch | 1 |
| Wind Advisory | 4 |
| Fire | |
| Red Flag Warning | 1 |
| Fire Weather Watch | 1 |
| Fog and smoke | |
| Dense Fog Advisory | 3 |
| Coast and beach | |
| Tsunami Watch | 1 |
| Coastal Flood Advisory | 3 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20172019
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.