Flash Flood Warnings in California, 2013

By month

92 of 244 flash flood warnings covering California in 2013 had a flash flood report inside them; 133 of 205 flash flood reports fell inside a warning, on average 63 minutes after it went out.

California, 2013

Each office's whole area, 2013

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.

• San Bernardino County104
• Riverside County47
• San Diego County38
• Inyo County37
• Kern County8
• Imperial County7
• Mono County5
• Los Angeles County5
• Sierra County4
• Tulare County4
• Ventura County4
• Tuolumne County3
• Plumas County2
• Nevada County2
• Placer County2
• Shasta County1
• El Dorado County1
• Santa Barbara County1
• Lassen County1

1. July 22, 201321flash flood warnings
2. August 31, 201320flash flood warnings
3. July 28, 201315flash flood warnings
4. August 30, 201315flash flood warnings
5. July 21, 201314flash flood warnings
6. September 7, 201312flash flood warnings
7. August 24, 201311flash flood warnings
8. August 29, 201310flash flood warnings
9. August 18, 20139flash flood warnings
10. August 25, 20139flash flood warnings
11. September 1, 20139flash flood warnings
12. September 4, 20139flash flood warnings

Alerts in force nowTornadoes on recordThe radar archive20122014

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.