Murray: I had this very discussion with Environment Canada's weather people at the Vancouver Boat Show last January. I asked them if they put a precautionary spin on the weather forecasts and they replied they did not do that. They said the range in the forecast winds was +/- 5 knots about the point-estimate. So when they forecast 15-25 knots it is simply +/- 5 knots about the point estimate. I "lost them" when I asked them whether the range was derived from a Bayesian PDF (Probability Density Function). I am still suspicious that they put a precautionary spin on things but they are not admitting to it. Note that you can talk to a weather forecaster for a fee. Evidently towing companies use this opportunity regularly.
I had a further discussion with Richard on Dauntless about this. He maintained that the weather models for the major areas use the same basic input information, regardless of the country of origin. Of course with his background, Richard consults the weather maps and makes his own decisions accordingly. This is one such map that might be useful:
http://www.opc.ncep.noaa.gov/P_e_sfc_color.png
Richard also mentioned that near shore areas are much more difficult to forecast because of the local geography has a very strong influence. (Richard: I hope I didn't misrepresent our discussions!)
Jim