A little more on Springs and Neaps
You have probably already noticed the red and blue print on the tide tables are colour coordinated with the days of Spring and Neap tides?
Looking at the tide table it is easy to visualise that there are approximately two spring and two neap tides per month. It worth having a good look at the tide tables as you can get a feel what is happening with the tide over time (Fig 5.25). Just by glancing at them we can quickly determine a trend, i.e., whether the tidal range will be coming less as we move towards neaps or getting bigger as we move towards springs.
If we look a little closer we can see that for Hamilton Sound the Highest tides are found on the 1st – 2nd of March a couple days after the new moon. There is a lag in the tide as it is affected by the gravitational pull of the moon and sun. You should note that there are also little printed pictures of the moon phases on the tide tables indicating whether it is a new or full moon spring tide. All these cues on the tide tables are useful but if you need specific information on tidal ranges, look at the day concerned and compare them to the Mean Ranges table on the relevant tidal curve page.
Mid Range – halfway between springs and neaps
At Port Hamilton the mean ranges of springs tides is 5.2m and mean range of neaps tides is 3.2m (Fig 5.23). The way to work out what the mid range will be is to take the difference between the Spring range and the Neap range 5.2m-3.2m = 2 then divide this difference between he ranges by 3. 2 / 3=0.6m. So the midrange low water is 3.2m+0.6m=3.8m and the midrange high water is 5.2m-0.6m=4.6m So any range between 3.8 and 4.6 can be considered midrange and half way between a neap and spring range (Fig 5.26)