(c) Plot C is the annual cycle in tidal range. Three measures of the range have been 

 used: the standard deviation of aU computed hourly values, the mean tidal range, and the 

 mean diurnal tidal range. These data are normalized with respect to the computed mean 

 range for the Atlantic coast and the computed diurnal range for the gulf and Pacific coasts. 

 In general, the standard deviation shows the least variability witli season and the diurnal 

 range shows the most. Calculations were first made for each month, and the monthly values 

 were averaged for 19 years. 



(d) Plot D shows the variability of each measure of range for tlie metonic cycle. The 

 anticipated 19-year cycle is apparent for each measure. These data also are normalized with 

 respect to the computed mean daily range. 



(e) Plot E gives the annual cycle of calculated low water parameters. The lowest point 

 for each month represents the lowest predicted tide for that month in any year of the 

 metonic cycle. The upper point, indicated by an x, represents the mean predicted low 

 water for that month, when all predicted low waters of the 19-year period are considered. 

 The intermediate points represent tlie means of the lower low water for each calendar day 

 averaged for each month. All data in this graph are normalized as indicated in (c) above. 

 Note that the MLW and MLLW plots represent a combination of the annual cycle in MSL 

 and the annual cycles in the tidal range. In nearly all cases, the annual cycle in MSL is 

 dominant. 



(f) Plot F is similar to plot E and normalized in the same manner, but presents data for 

 the metonic cycle. The MLW and MLLW graphs show tlie expected 19-year cycle. The 

 predicted extreme low tides for each year show an unexpected periodicity of about 6 years. 

 No effort has been made to determine the reason for this periodicity. 



(g) Plots G and H are similar to plots E and F but are normalized as indicated in 

 (c) above. The annual cycles follow approximately the same patterns as the mean sea levels. 

 The 19-year cycle is apparent in the MHW and MHHW data. The period of approximately 6 

 years appears in the extreme predicted high waters as well as in the predicted low waters. 



Plots for each of the NOS reference stations and for a few nonreference stations are 

 presented in Appendix B. The data appearing on these plots for aU locations discussed in 

 this report are summarized in tables shown in Appendix B. 



Values of MHHW, MHW, MLW, MLLW, standard deviation, mean range, and the mean 

 diurnal range based on these calculations are given in Table 7. Observed values of the mean 

 and diurnal ranges obtained from NOS bench-mark sheets are also shown in the table. AU of 

 the calculations in this report are based on the period 1963 to 1981; no storm effects are 

 included. The NOS values are based on observations, generally for the period 1941 to 1959, 

 and include minor storm effects. Thus, exact agreement is not to be expected and the NOS 

 values for range are expected to be slightly larger tlian those based on astronomical 

 calculations. 



The definitions used in the computer program to derive the high and low water datums 

 differ slightly from those used by NOS for dealing with observations. In the computer 



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