What is a tide?
This is not as obvious as it may sound – it is not just the rise and fall of the water in our seas and oceans (tides are only one of the contributing factors in this rise and fall). A tide is the regular and predictable movement of water caused by astronomical phenomena – the way the earth, moon and sun move in relation to each other and the force of gravity. These are the values that you can see in tide tables. Movement of water caused by meteorological effects (for example winds and atmospheric pressure changes) are called surges. These are not easily predictable and require powerful computers and sophisticated software to predict just 36 hours in advance. These are the reasons why tide table predictions do not always agree with observations. POL develops storm surge models for flood forecasting that have been run at the Met Office since 1978. (A large positve storm surge can add a few metres to the predicted water level.
This is not as obvious as it may sound – it is not just the rise and fall of the water in our seas and oceans (tides are only one of the contributing factors in this rise and fall). A tide is the regular and predictable movement of water caused by astronomical phenomena – the way the earth, moon and sun move in relation to each other and the force of gravity. These are the values that you can see in tide tables. Movement of water caused by meteorological effects (for example winds and atmospheric pressure changes) are called surges. These are not easily predictable and require powerful computers and sophisticated software to predict just 36 hours in advance. These are the reasons why tide table predictions do not always agree with observations. POL develops storm surge models for flood forecasting that have been run at the Met Office since 1978. (A large positve storm surge can add a few metres to the predicted water level.) There is also wave movement which is purely wind generated an
