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11/17/2023 7:13 am  #1

SHOM or Proudman Tides for routing analysis.

I'd like to carry out a statistical routing analysis for the Fastnet race for the past 10years considering not only wind but also current.

For wind I'm going to use the Copernicus reanalysis grib files. That's all straight forward.

For current I intent to use SHOM or Proudman tides (unless there's an even better way(?) ). So far I don't have a subscription, so before doing that I'd like to understand a few things.

1) Are both (Proudman and SHOM) usable in Expedition? On the Expedition website under sales I only find SHOM tidal currents for "Northern and Western France"
2) If both are usable: What is the difference between them? Is there one model considered to be "better"?
3) How far do the models rach back into the past? Is it possible to use them for routings for the past 10years?

4) And now the tricky one:
I expect that the SHOM / proudman models use different tidal coefficients for different dates, so the strength of the current in a certain area will vary over the tidal cycles.
While I can offset the starting time of the multi-year routings to always have the same relation to high tide like on Fastnet starting day (by offsetting the routing starting times by for example one tidal cylce / 12h 25min) and thereby getting at least the right current direction this would however lead to varying current strengths depending on the varying tidal coefficient.

So ist there any way to use the "fixed" current of the 2025 Fastnet with its tidal coefficient for all the routings with the weather from the past 10 years?


11/17/2023 10:15 am  #2

Re: SHOM or Proudman Tides for routing analysis.

We have stopped selling new SHOM and Proudman licences as there is effectively no demand now we have the Copernicus current forecasts.

They have older data, but it is in NetCDF format.

It wouldn't work to use a current forecast from this year.

One possible and easy solution is to use the Admiralty tidal diamonds. We have a databe of those.


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