Neap and Spring tides explained

04 February 2020

Tides are an extremely important factor in the sailing world. It is important to have a basic understanding of how tides work because it can be the difference between a fantastic, smooth fast passage, or a boring, slow and potentially lumpy one.  It could also be imperative to get into a harbour at high tide rather than at low tide where it may be impossible. Tides are very stable and can be predicted with a fair amount of certainty, hence tide tables that can be found in the Almanac, tide table booklets, or on tidal Apps.

We know the tide rises and falls, giving us high tides and low tides but why does this happen?

The tides are governed by earth's position in relation to the moon and sun. Both the moon and the sun pull at the earth’s bulge of water and this is what causes tides.  Simply put, when the sun and moon are in line with the earth, the gravitational pull is at its greatest. This means that high waters are very high and low waters are very low.  This is the spring tide.  When the moon and sun are 90 degrees to each other, the gravitational pull is its weakest, thus low high waters and high low waters, this is neap tide.

Just remember spring tides are high high tides and low low tides giving a large tidal range between the two, neap tides are low high tides and high low tides giving a small range between the two.

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