by Des Ryan
As technology advances, information systems on tidal effects become more and more sophisticated, and greater and greater help to the cruising sailor trying to negotiate areas that are particularly affected by tidal flows.
3D bathymetric (depth) schematic of St Catherine’s Point - Isle of Wight
The Straits of Gibraltar is one example, the waters off Australia's northern coastline is another and the popular racing waters of the Solent is yet another.
A high-resolution tidal model by Tidetech for the Solent and UK south coast, for instance, has revealed a complexity of tidal streams and currents in these waters not previously well understood.
The model details an area including Southampton Water, the entire Solent, the southern sectors of the Isle of Wight and the entrance to Chichester Harbour.
Tidal data of this resolution has previously been the domain of government agencies, oil companies and specialist environmental modelling agencies with access to super computers. Now able to be managed on powerful laptops, the complex calculations required to create the models have been translated into easy-to-view visual tools available to competitive sailors and maritime users.
Tidetech, an oceanographic data specialist comprising the world’s foremost tidal surge modelling scientists and navigation experts, is leading the way.
Lead scientists Dr Roger Proctor and Dr Roger Flather have between them over 60 years of research experience with the Proudman Oceanography Centre (now the National Oceanography Centre), the world’s leading centre for tidal prediction. Dr Proctor also provided elite sailing support to the British Olympic Sailing Team at five consecutive Games between 1988 and 2008.
Tidetech director Penny Haire said sailing in the Solent, for instance, is more often influenced tactically by tides than by wind.
'The south coast model clarifies various aspects of Solent currents that many sailors have found tricky in the past… for example, the model clearly shows the area of reduced tide in the lee of the Bramble Bank along with the complexities of the Hill Head region.
'It’s quite revealing, as there are areas of localised tidal acceleration that occur within very short distances.
'Over Sturbridge Shoal and at Lepe, for example, there’s a visible half-knot variation within 100m distance and that could make a considerable difference to yachts within this range.'
The detailed information is available in GRIB format but also in an online viewer that allows any subscriber to see the relevant data on a computer, iPad or smart phone and make their own custom tidal atlas which can be downloaded as a PDF and printed for taking afloat.
A subscription to Tidetech costs as little as around $100 per year for the basic version, and depending on where you sail, great value for money. For more information go to their http://www.tidetech.org!website.