National Weather Service United States Department of Commerce

PUBLIC INFORMATION STATEMENT

Wednesday, March 20, 2013

...2013 National Flood Safety Awareness Week...

The National Weather Service continues its annual Flood Safety Awareness Week today through Friday, March 22nd. This year the National Weather Service is also commemorating the centennial anniversary of the Great Ohio Valley Flood of 1913 which occurred between March 23 and 27th and was the largest weather disaster in Ohio’s history.

Historical Hurricane Tracks near Ohio

The theme for today is tropical cyclones and inland flooding. June 1 through November 30 is the official hurricane season. During each season, an average of 10 storms will develop in the Atlantic Basin, 6 of which will likely become hurricanes. In addition to wind, tornadoes, and storm surge flooding, many tropical systems produce inland freshwater flooding. Tropical cyclones can have life threatening effects hundreds of miles inland.

Northern Ohio and northwestern Pennsylvania are not the first places you think of as being in danger of hurricanes, however in the past century dozens of hurricane remnants have moved over the region. Remnants of Hurricanes Frances and Ivan in September of 2004 brought torrential rain twice within a weeks’ time resulting in widespread flooding in the Ohio Valley. These remnant storms can pose just as dangerous a flood threat as a hurricane making landfall. When a hurricane dissipates as it moves inland, it often takes several days to rain out all the tropical moisture it had carried. The remnants will also often merge with other weather systems and frontal boundaries which can increase the rainfall.

Factors affecting inland flooding.

  • Storm Speed- The slower the system moves, the more time for the rains to fall over a location.
  • Orography-Lifting of the warm, moist tropical air over geographical barriers, such as hills and mountains. Also the gradual increase in elevation as the system moves inland amplifies and intensifies the rain.
  • Interaction with other weather features- Agnes (1972) fused with another storm system, producing floods in the northeast U.S., which caused 122 deaths and $3.2 billion dollars in damages.
  • Antecedent conditions-The wetness or dryness of the soil, the existing capacity of the streams and rivers, ponds and lakes and reservoirs.

 

Additional information about Flood Safety Awareness Week can be found at WWW.FLOODSAFETY.NOAA.GOV or http://tadd.weather.gov. For more information about the Great Ohio Valley Flood of 1913 please visit http://mrcc.isws.illinois.edu/1913Flood/.