Tropical Cyclone Inland Flooding
The following web story is a transcription from the National Weather Service regarding flooding safety awareness week. This is the third of a five part series on flooding safety which will run each day during New York's flooding safety awareness week. Today’s topic is tropical cyclone inland flooding.
A tropical cyclone is a generic term for hurricanes, tropical storms or typhoons. Typically, you will hear about the strong winds and storm surge flooding that are both associated with a hurricane that makes landfall. However, intense rainfall, not directly related to the wind speed of a tropical cyclone, often causes more damage. Did you know that since the 1970s, inland flooding has been responsible for more than half of the deaths associated with tropical cyclones in the United States? Typically, greater rainfall amounts and flooding are associated with tropical cyclones that have a slow forward speed or stall over an area. Therefore, it is very important for meteorologists to monitor how fast or slow these systems move. Here are a few items that we should all be aware of:
What do I need to know about inland flooding from tropical cyclones?
- Inland freshwater floods accounted for more than half (59%) of U.S. tropical cyclone deaths over the past 30 years.
- Rainfall is typically heavier with slower moving storms as slower moving tropical cyclones allow heavy rain to persist over a location.
What types of inland flooding are caused by tropical cyclones?
- Flash flooding occurs in creeks, streams, and urban areas within a few minutes or hours of excessive rainfall. Rapidly rising water can reach heights of 30 feet or more. Streets can become swift moving rivers and underpasses can become death traps.
- River flooding occurs from heavy rains associated with decaying hurricanes or tropical storms, and in extreme cases, river floods can last a week or more.
How do I know how severe a flood will be?
Within flood warning products, the National Weather Service conveys the magnitude of observed or forecast flooding using flood severity categories. These flood severity categories include minor flooding, moderate flooding, and major flooding. Each category has a definition based on property damage and public threat.
- Minor Flooding: Minimal or no property damage, but possibly some public threat or inconvenience.
- Moderate Flooding: Some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations are necessary.
- Major Flooding: Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.
The impacts of floods vary locally. For each National Weather Service river forecast location, flood stage and the stage associated with each of the flood severity categories are established in cooperation with local public officials. Increasing river levels above flood stage constitute minor, moderate, and major flooding. Impacts vary from one river location to another because a certain river stage (height) in one location may have an entirely different impact than the same level above flood stage at another location.
The topics that we will focus on the rest of this week are as follows:
Thursday: Snowmelt and ice jams, including the spring flood outlook
Friday: Flood safety
For more on your weather forecast, click on “Weather” and then the “Live Triple Doppler Radar” tab on our weather page. Make sure you refresh the Doppler radar to see the very latest information, as well. Furthermore, we have our new Interactive Doppler Radar on our website. You can zoom down to street level with Interactive Doppler Radar. You are in total control of where the radar can zoom in. Give it a try. In addition, you may tune to NBC Weather Plus on Time Warner Cable digital channel 133 or over the air 3.3 to get the very latest weather updates locally and nationally. Plus, click on Severe Weather Tab to see detailed county watches, warnings, and advisory information. In addition, you can “follow” along with me on Twitter by either clicking on the “follow” button on the Twitter section of our weather page www.cnycentral.com/weather or by visiting www.twitter.com/PeteWeatherBeat.
