UKC

Was climbing at Fisherman's Ledge on the wknd and a local let us know that the tide table i always use for the purbeck crags (Connor's Cove/Seacombe/Dancing ledge), which is the ADMIRALTY EasyTide profile for Swanage, is actually basically reversed to what you experience at the crags there. Swanage Bay gets the double high, whereas this bit of coastline (to the east of Anvil Point) gets kind of a double low - even though they are so close!

Looking on the internet today seems that the tides are weird here as it's a 'amphidromic' or 'nodal point'. 

With that in mind - do any locals think this tidal profile is decent, for Dancing Ledge from: WillyWeather? https://tides.willyweather.co.uk/sw/dorset/dancing-ledge.html.

Someone must have generated some harmonics for that coastline? it's so popular for sailing, fishing, diving etc. Although i guess there are no ports so maybe no one will have been able to monitor water levels to generate harmonics....?

I know tides basically does't matter here for most climbing cos the tidal range is so low, but it's just kinda interesting - and also nice to know for some of the DWS where it's not deep water like it is at Connor Cove/Conger area or Funky Wall. At a Spring Tide, a 1.5m difference in tidal height could make all the difference at some spots (Aquanauts) - or for traversing into the start of routes at the base of the Conger and not getting wet feet. 

Any general tide knowledge welcome, pretty interesting the tidal streams round there. 

George. 

The amphidromic point is where there is virtually no tidal range. Think of a coffee as you carry it, it slops from side to side but the centre stays at the same level. I think the amphidromic point on the south coast is at Kimmeridge Bay. The double high tides are caused by the Isle of Wight.

You're probably best asking on angling or sailing forums. Worldseafishing would be the angling one to try first, there are regional subforums and a boat fishing one you should ask in.  Then update the access notes in the crags on here when you have the info

thanks for the responses, overall i think the WillyWeather Dancing Ledge tidal forecast should be taken with a pinch of salt as it's the most eastern location of a stretch of tidal forecasts all using the same profile.  (https://tides.willyweather.co.uk/sw/dorset/dancing-ledge.html) . The levels from this website seem to just be translated profiles from the closest secondary port/hydrographic office location - which i think is Swanage in this case - but it's at the furtherst away forecast location and evidently has very different tidal behaviour . So Dancing Ledge, Anvil Point, Durlston Head and Pevril Piont and Swanage all have the same profile on Willy Weather, just translated HT and LT timings as you move west/east.  Then St Alban's Head uses a different profile through to Kimmeridge, and the HT and LT times for these two profiles are almost reversed! I think... The eastern profile (St Alban's, Kimmeridge, Lulworth etc)  is definitely more normal looking. 

Therefore, i think it's still a bit of a mystery, i think you're never going to a get a proper answer along this coastline as there is no secondary port , probably best bet would be understanding how the tide relates to tides at Mupe Bay or Swanage where there are proper tidal models (being hydrographic office standard/secondary ports). Or if you had a tidal stream map you could look at the movement of water in relation to these locations and try to estimate? 

not that is really matters for the climbing much anyway, just pretty interesting. 

Reply to Toerag: Bang on, the sailing forums would know! i bet they would love to chat about it too! might try and find one and give it a go. 

zz4: thanks for analogy - i think the IoW explanation is a bit of a myth/oversimplification, may be part of the reason for double tides but it is more complex than that i believe (Poole harbour, bathymetry, and tidal streams)

Thanks all, George. 

From personal experience I doubt the sailors actually know much, the local fishermen like my brother who's been climbing and working that stretch of coast for about fifty years knows though!

Thank you for this. Amphidromic - what a lovely word - ancient Greek for "running around". Love the coffee analogy.