height selected on the hour), and various extreme and/or mean water level 
statistics were computed. 
Results 
51. Tides at the FRF are semidiurnal with both daily high and low 
tides approximately equal. Tide height statistics are presented in Table 7. 
Figure 17 plots the monthly tide statistics for all available data, and 
Figure 18 compares the distribution of daily high and low water levels and 
hourly tide heights. The monthly or annual mean sea level (MSL) reported is 
the average of the hourly heights, whereas the mean tide level is midway 
between mean high water (MHW) and mean low water (MLW), which are the averages 
of the daily high- and low-water levels, respectively, relative to NGVD. Mean 
range (MR) is the difference between MHW and MLW levels, and the lowest water 
level for the month is the extreme low (EL) water, while the highest water 
level is the extreme high (EH) water level. 
43 
