Tide Tables and Daily Range of Tide
Fig 5.22 is a the tide table for Hamilton Sound on page 72 of the RYA Training Almanac. We will be using the 3rd March.
We are interested in looking at the ‘range of tide’ for this day as we use it all the time when calculating and investigating tidal heights. The range of any particular tide is the difference between the high and low water of any two consecutive entries in the tide table.
On the 3rd March we have:
At 0306hrs SP the tide level is 6.0m above chart datum.
At 0935hrs SP the tide level is 0.0m above chart datum, so it is actually at the same level as chart datum!
At 1534hrs SP the tide level is 5.9m above chart datum.
At 2138hrs the tide level is 0.6m above chart datum.
The tidal range between the first high tide and proceeding low tide is 6.0m
The tidal range between the first low tide and second high tide is 5.9m
The tidal range between the second high tide and proceeding low tide is 5.3m
So we can see clearly that there is a difference in the tidal ranges even on the same day and that the tidal range is becoming less. This highlights the fact that the earth is passing through two different tidal bulges, and we are moving from a period of spring tides to neap tides or vice versa.
You will also see that tidal levels and ranges are never constant and constantly fluctuating and particularly handy for us to think in terms of Mean tide levels, MHWS, MHWN, MLWS and MLWN.