Will A Tide Clock Work For My Location?

December 29, 2020

Will A Tide Clock Work For My Location?

4 minute read

This is a question we often get asked and it's fairly straightforward, once you understand more about how tides and tide clocks work.

What Is A Tide Clock?

A tide clock is essentially a dial (just like a time clock) with a timed mechanism. The key differences are the time it takes for the hands of the clock to rotate, and the markings around the edges.

Rather than the mechanism rotating once every 12 hours, like a regular clock, the mechanism rotates once every 12 hours and 25 minutes. This is roughly the time that passes between two high tides. This tells us that there are just under two high tides and two low tides daily. This rotation is due to the moon's gravitational pull on the Earth's oceans. 

In the position where a time clock would have the number 12, a tide clock has the words 'High Tide', and in the position where a time clock would have the number 6, a tide clock has the words 'Low Tide'.

ClimeMET CM4305 Tide Clock

Working clockwise from High Tide at the 12 o'clock position, the tide clock shows the tide falling until you reach Low Tide at the equivalent of 6 o'clock. Continuing clockwise, the clock then shows the tide rising from the 6 o'clock position until you get back to the 12 o'clock position.

Here at ClimeMET, we also offer a tide clock with the more traditional 'High Water' and 'Low Water' wording, which is available here.

A Bit About Tides

The moon's gravitational pull generates tidal force which is responsible for the first high tide of the day. The second high tide of the day is caused by the centrifugal force of the Earth and Moon orbiting a common centre of mass.

During the new moon and the full moon each month, the sun, the moon and the earth come into alignment, increasing the pull on the tides to the maximum. In effect, the gravity of the sun reinforces the gravity of the moon. Given this, tide clocks should be set up (or reset) on the new moon or full moon, ideally around noon or midnight, for greatest accuracy.

As mentioned, most tide clocks work on a timed mechanism of 12 hours and 25 minutes but in reality, the tides follow a pattern closer to 12 hours 25 minutes and 14 seconds. This doesn't sound like much of a difference, but 14 seconds per tide can add up to around 15 minutes a month, and would mean that your tide clock won't be as accurate as it once was, so even for the most regular of tides, we recommend resetting your tide clock against a tide table from time to time.

We would also recommend you set up or reset your clock either on the full or new moon, ideally around noon or midnight for greatest accuracy, as these would typically be the local high tide times. 

How To Check Your Local Tides

When a customer gets in touch with us at ClimeMET and asks us if we think a tide clock will be suitable for their location, here's what we do:

  • First, we ask the customer to specify their favourite beach. This is because the tide varies along the coast, so you'll need to set your tide clock to track one specific location. The shape, orientation and winds for a particular area also play a role.
  • Next, we take a look at the tide times using an online tide table. We look at the difference from one high tide to the next. Remember, we are looking for this to be around 12 hours 25 minutes. If the first high tide of the day is at 8am, for a very regular tide, we'd expect to see the next high tide at 8.25pm.
  • If the gap between the two high tides is close to 12 hours and 25 minutes, we'll spot check a few different days to confirm this, but generally a tide clock would be suitable.
  • If the tide isn't that close to 12 hours and 25 minutes, we'll look at a few more readings before making a decision. It may be that the tide is 10 minutes shorter, but the next tide is 10 minutes longer, and over the course of a week, any variations are evened out.
  • If the difference between the high tides is significantly different each day, or is not close to 12 hours and 25 minutes, then unfortunately a tide clock is likely to be unsuitable for this location.
  • Customers often ask about tides abroad when purchasing a tide clock for a friend or family member. Our tide clocks can be used worldwide! Simply follow the method above to check their local tide - it's usually absolutely fine.


    What To Watch Out For

    As well as looking at the tide times online, it's worth looking at the location on a map and seeing what the surrounding coastline looks like, as this can provide a lot of insight. There are some tides in the UK and abroad that don't fit a regular pattern and often tide clocks aren't suitable for customers in these areas. A couple of examples:

    Southampton is home to a fascinating double tide, which is explained wonderfully by the ABP. This also affects the Isle of Wight.

    The River Thames has tidal parts. In open water, the tide tends to come in and go out at roughly the same pace, but the friction caused by the river bed often means that the tide comes in at one speed, and goes out much more slowly, making it harder to track.

    If you notice your tide clock doesn't seem to be rolling in on time, you can reset using a recent tide table for your desired location. Note regular adjustments will help maintain accuracy over time. 


    What is a tide clock?

    • A tide clock is a special type of clock that indicates the state of the tide at a particular location, showing high and low tide times over a 12-hour and 25-minute cycle.

    How does a tide clock work?

    • A tide clock works by rotating once every 12 hours and 25 minutes, which corresponds to the average time between high tides. The clock face is marked with "High Tide" and "Low Tide" positions instead of traditional hour markers.

    How accurate are tide clocks?

    •  While tide clocks are generally accurate, they may drift slightly due to the exact tidal period being closer to 12 hours and 25 minutes and 14 seconds. Regular resetting based on tide tables can help maintain accuracy.

    Can I use a tide clock anywhere?

    • Tide clocks are most suitable for locations with regular tidal patterns. Some areas, such as those with double tides or tidal rivers, may not be suitable. Check your local tide times to determine suitability.

    Why might a tide clock not be suitable for certain locations? 

    • In areas with irregular tides, double tides, or significant differences in tidal intervals, a tide clock may not accurately reflect the local tide pattern

    Can I use a tide clock for international locations?

    • Yes, you can use a tide clock for international locations. Just follow the same method of checking the local tide times and setting the clock accordingly. (Include the yes you can use a tide clock for international locations/ is in there but not too much info on it)

    What is the difference between 'High Tide' and 'High Water'?

    • "High Tide" and "High Water" are interchangeable terms. Some tide clocks use one term over the other based on traditional wording preferences.

    Our complete range of ClimeMET Tide Clocks can be viewed here.