Flash Flood Warnings in Maryland, 2009

By month

20 of 41 flash flood warnings covering Maryland in 2009 had a flash flood report inside them; 32 of 34 flash flood reports fell inside a warning, on average 45 minutes after it went out.

Maryland, 2009

Each office's whole area, 2009

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.

• Cecil County7
• Baltimore County6
• Montgomery County6
• Harford County5
• Caroline County5
• Prince George's County4
• Carroll County4
• Howard County3
• Queen Anne's County3
• Talbot County3
• City of Baltimore2
• Anne Arundel County2
• Wicomico County2
• Worcester County2
• Kent County2
• Allegany County1
• Somerset County1
• Charles County1
• Calvert County1
• Frederick County1

1. August 28, 200910flash flood warnings
2. August 22, 20097flash flood warnings
3. August 2, 20094flash flood warnings
4. June 10, 20093flash flood warnings
5. May 26, 20092flash flood warnings
6. June 4, 20092flash flood warnings
7. June 9, 20092flash flood warnings
8. July 31, 20092flash flood warnings
9. May 7, 20091flash flood warnings
10. May 23, 20091flash flood warnings
11. May 29, 20091flash flood warnings
12. June 3, 20091flash flood warnings

Alerts in force nowTornadoes on recordThe radar archive20082010

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.