Because of the limited availability of observed hurricane surge data for 

 the open coast, design analysis for coastal structures is not always based on 

 observed water levels. Consequently a statistical approach has evolved that 

 takes into account the expected probability of the occurrence of a hurricane 

 with a specific CPI at any particular coastal location. Statistical eval- 

 uations of hurricane parameters, based on detailed analysis of many 

 hurricanes, have been compiled for coastal zones along the Atlantic and gulf 

 coasts of the United States. The parameters evaluated were the radius of 

 maximum wind R ; the minimum central pressure of the hurricanes p ; the 

 forward speed of the hurricane V „ while approaching or crossing the coast; 

 and the maximum sustained wlndspeed W at 10 meters (33 feet) above the mean 

 water level. 



Based on this analysis, the U.S. Weather Bureau (now the National Weather 

 Service) and U.S. Army Corps of Engineers jointly established specific storm 

 characteristics for use in the design of coastal structures. Because the 

 parameters characterizing these storms are specified from statistical con- 

 siderations and not from observations, the storms are terms hypothetical 

 huvrn-canes ov hypohuvrn-aaneS' The parameters for such storms are assumed 

 constant during the entire surge generation period. Examples of such 

 hypothetical storms are the Standard Project Hurricane ( SPH) and the Probable 

 Maximum Hurricane (PMH) (National Weather Service, 1979). The mathematical 

 model used for predicting the wind and pressure fields in the SPH is discussed 

 in Chapter 3, Section VII, 2 (Model Wind and Pressure Fields for Hurricanes). 

 The SPH is defined as a "hypohurricane that is intended to represent the most 

 severe combination of hurricane parameters that is reasonably characteristic 

 of a region excluding extremely rare combinations." Most coastal structures 

 built by the Corps of Engineers that are designed to withstand or protect 

 against hurricanes are based on design water level associated with the SPH. 



The construction of nuclear-powered electric generating stations in the 

 coastal zone made necessary the definition of an extreme hurricane, the PMH. 

 The PMH has been adopted for design purposes by the Nuclear Regulatory 

 Commission to ensure public safety and the safety of nuclear-powered facil- 

 ities. The PMH is defined as "hypothetical hurricane having that combination 

 of characteristics which will make the most severe storm that is reasonably 

 possible in the region involved if the hurricane should approach the point 

 under study along a critical path and at an optimum rate of movement." 



(3) Predicting Surge for Storms Other Than Hurricanes . Although the 

 basic equations for water motion in response to atmospheric stresses are 

 equally valid for nonhurricane tropical and extratropical storms, the struc- 

 ture of these storms is not nearly so simple as for hurricanes. Because the 

 storms display much greater variability in structure, it is difficult to 

 derive a standard wind field. Moreover, no system of storm parameters has 

 been developed for these storms, such as has been done for hurricanes using 

 such parameters as radius to maximum winds, forward motion of the storm 

 center, and central pressure. 



Criteria, however, have been established for a Standard Project Northeaster 

 for the New England coast, north of Cape Cod (Peterson and Goodyear 1964). 

 Specific standard project storms other than those for hurricanes are not 

 presently available for other coastal locations. Estimates of design storm 

 wind fields can be made by meteorologists working with climatological weather 



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