A couple of you have asked “what is an areal flood warning?”, and this provides me with the best opportunity to explain the four kinds of flooding NWS will alert for. 1) Areal Floods Areal floods are triggered when rainfall exceeds the flood guidance over a longer period than flash flooding. Areal flood warnings and watches generally are concerned with smaller hydrologic features, such as creeks and streams. Areal flood warnings and advisories are polygon warnings. Areal flood watches are issued when heavy rainfall could cause creeks and streams to burst their banks. Areal flood advisories are issued when river and stream flows are elevated and could burst for ponding or minor flooding in urban areas 2) River Flooding Self-explanatory. River flood warnings (flood warnings) are triggered for specific locations along a river that will exceed the river’s defined flood stage, although the NWS codes warn the entire county affected. For example, if the Potomac River at Little Falls (near Great Falls) hits 10 feet, a flood warning for Montgomery and Fairfax Counties will be triggered. 3) Flash Flooding Flash flooding occurs when a large amount of rain happens in a short amount of time, usually associated with thunderstorms. Flash flooding is extremely dangerous and is not necessarily confined to rivers and streams and can occur in any floodable area. Flash Flood warnings are polygon-based warnings 4) Coastal Flooding Flooding of areas along a coastline and restricted to that coastline. These are issued for whole counties along this tier: Statement, Advisory, Watch, Warning. Statements are only issued by a few offices for nuisance flooding Coastal Flood Advisories are issued for nuisance or minor flooding. Coastal flood watches are issued when minor to major coastal flooding is expected or occurring. Coastal Flood Warnings are issued when major coastal flooding is expected or occurring This type of flooding poses a serious threat to lives and property. Coastal flood alerts are only issued along major coastal areas and the great lakes, Upstream areas don’t qualify. Coastal flood alerts are issued for NWS zones which may or may not include whole counties And there you have it, the four types of flooding!
Posted on: Fri, 12 Jul 2013 17:38:05 +0000
Trending Topics
Recently Viewed Topics
© 2015