Flash Flood Warnings in California, 2010

By month

30 of 126 flash flood warnings covering California in 2010 had a flash flood report inside them; 35 of 89 flash flood reports fell inside a warning, on average 103 minutes after it went out.

California, 2010

Each office's whole area, 2010

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 County55
• Los Angeles County24
• Riverside County19
• Inyo County9
• San Diego County8
• Mono County7
• Kern County5
• Santa Barbara County4
• Orange County3
• Alpine County3
• Sierra County3
• Sonoma County2
• Imperial County2
• Madera County1
• Mariposa County1
• Tuolumne County1
• Siskiyou County1
• Lassen County1
• El Dorado County1
• Ventura County1
• San Luis Obispo County1

1. August 26, 201017flash flood warnings
2. December 22, 201016flash flood warnings
3. February 6, 20109flash flood warnings
4. January 21, 20108flash flood warnings
5. August 25, 20107flash flood warnings
6. December 20, 20106flash flood warnings
7. February 27, 20105flash flood warnings
8. July 16, 20105flash flood warnings
9. January 18, 20103flash flood warnings
10. January 20, 20103flash flood warnings
11. January 22, 20103flash flood warnings
12. February 7, 20103flash flood warnings

Alerts in force nowTornadoes on recordThe radar archive20092011

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.