Storm & Security

Storm Surge? SEASONAL/FORECAST What Is continued on the ability to communicate life-saving information and in making decisions during a storm event. 12 PEOPLE IN THE KNOW 2013 / STORM & SECURITY PROTECTION STORM & SECURITY PROTECTION / FORECAST 2013 13 Pete Fickenscher, NOAA/NWS/WR/RFC Sacramento Realizing the risks association with coastal flooding as a result of storms requires using AccuWeather.com reports the NOAA thewords and terms commonly understood. Towith ensure clear communication, East Coast to the Gulf of total seasonal probability of landfall can be forecast help Mexico is at most risk for landfall this season. statistical skill. With landfall a function of varying climate and the National Weather Service have defined the following terms: The Weather Research Center (WRC), Houston, TX, conditions, the probability of landfall can be developed through believes there is "a high chance" that three or more tropical statistical analyses of all U.S. hurricane and named storm landfall Storm Surge – The abnormal rise of water generated by a storm over and above storms or hurricanes will make landfall somewhere along the U.S. events during the 20th century (1900 to 1999). Long-term the normal astronomical tide, and expressed in terms of height above predicted or coast. According to WRC meteorologist Jill Hasling, the Gulf statistics show that, on average, the more active the overall expected tide levels. Coast has a 70 percent chance of experiencing the landfall of a Atlantic basin hurricane season is, the greater the probability of Because storm surge represents tropical storm not U.S. hurricane landfall, CSU states. the deviation from normal tide levels, it is or hurricane this year. The coast from Georgia to referenced to a vertical or tidal datum. A vertical datum is a base elevation usedthe second highest risk with a 60 percent North Carolina has as "We anticipate an above-average probability for major a reference from which to measure heights coastline and chance. hurricanes making landfall along the United States(or depths). A tidal datum is a base elevation defined by a certain phase of the tide. WRC uses a model called Orbital Cyclone Strike Index in the Caribbean," writes Klotzbach. (OCSI), which uses Here are CSUʼs probabilities ofdue to the combination of storm surge and the the solar cycle (an indication of the solar a 2013 U.S. landfall (figures Storm Tide – The water level systemʼs orbit) datum. in parenthesis represent averages for theterms of height above a vertical or tidalto predict the risk for coastal residents each hurastronomical tide, and expressed in last century): ricane season. The OCSI model is based on the premise that • Entire U.S. coastline: 72 percent (52 percent) Inundation – The total water level that occurspercent on normally dry ground as a result of reflected in the global circulation there are orbital influences • U.S. East Coast including Florida peninsula: 48 the storm tide, and expressed in terms of height of water, in pattern on the sun as well as the global circulation pattern feet, above ground level. NOAA defines inundation (31 percent) as the total water level on Earth. • Inundation provides the peninsula to Brownsville, TX: understood method for Gulf Coast from Florida most clearly and commonly on normally dry ground. communicating percent) WRC also foresees long hurricane 47 percent (30 storm surge-driven coastal flooding. As such, the National Hurricanea high probability for a NOAA. Photo courtesy Center's (NHC) official there is a provide storm surge-inducedseason this year. While indications were low (22 percent) of a flooding information The CSU team adds forecasts 61 percent probability for in terms major hurricane feet of into the Caribbean. The at least oneof inundation, ortracking water, above ground level. cyclone developing as early as May this year, there is a higher probability (55 percent) of a tropical cyclone as late as average for the last century is 42 percent. Understanding these terms when used in a National Hurricane Center official forecast has significant implications November.

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