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Sea Swimming Conditions. By Paul Smith. Contents. Tides Currents Wind Weather. Tides. Each 25 hour period is divided up into 4 tides (approx 6.25 hours apart). There are 2 high and 2 low tides within this period . At low tide the sea retreats and usually sand will appear .
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Sea Swimming Conditions By Paul Smith
Contents • Tides • Currents • Wind • Weather
Tides • Each 25 hour period is divided up into 4 tides (approx 6.25 hours apart). • There are 2 high and 2 low tides within this period. • At low tide the sea retreats and usually sand will appear. • At high tide the sea will reach its furthest point up the beach (often marked by dried seaweed and small pieces of driftwood). Tide Tables Tables showing the tide times and the height of the tides can be picked up at surf shops, the marina and online (there is even an iphone app!).
Tides • 12 Part Rule • During each tidal period (6.25 hours) the amount of sea water that moves can be divided into 12 equal amounts. • When the tide begins to Flow or Ebb in the first hour, 1/12th of the tidal range will pass through, in the second hour a further 2/12th and in the third and fourth hour 3/12th, for the fifth & sixthhour the tidal range slows down to 2/12th’s and 1 /12th. • So you can calculate from this that the tide is at it’s strongest in the 3rd and 4thHour (mid-tide).
Tides • The sea will retreat furthest and move up the beach furthest each spring tide (when there is a full or new moon). • There will be least movement of the sea during a neap tide (usually about 7 days after a Spring tide). • Typically a spring tide will have a tidal range of up to 7 metres whereas as Neap could be as little as three Metres.
Currents Current direction When the tide goes out (ebbs) the current will move to the west. When the tide comes in (floods) the current will move to the east. Tide in Tide out
How does this affect us as sea swimmers • Understanding tides and currents is helpful - as swimming with the tide can sometimes make it about 50% faster/easier for us. • Swimming against it can make it 50% slower/harder. • For example it can take 20 minutes to swim with the current between the piers but if you swam the other way it could increase to 40 minutes. • During spring tides these currents can have even more power and are particularly strong mid tide.
Weather Forecasting Weather It’s very important before going swimming to check the weather forecast (as well as the tide tables). http://www.visitbrighton.com/site/tourist-information/tide-timetables I find www.xcweather.co.uk very useful. It provides forecasts every three hours for the next five days (including wind direction, wind speed, temperature and whether it’s going to be sunny/cloudy/misty etc.
Wind The wind is an important feature of sea swimming and in most cases creates waves. In Brighton winds are mostly from the south west (prevailing winds) If a wind comes from the north you will have a flat sea! Wind from the south produces a sea with waves. Wind from the South or South West often produces the roughest seas (sometimes called swells) If you plan your swims to catch the tide and you have the wind behind you it will increase your speed significantly.
Wind • Measuring wind speed • The Beaufort Wind Force Scale measures wind speed between Force 0 – 12. • 0 is a completely flat mirror like sea with almost no wind. • 12 is a completely white sea with driving spray and very poor visibility. • Wind speed would be above 70 miles per hour. • Wave height on the beach would be well in excess of 3 metres (and considerably higher out at sea) http://en.wikipedia.org/wiki/Beaufort_scale
