bigal.nz 59 Posted April 6, 2021 Share Posted April 6, 2021 Where do you find tide stream data for north cape - or at least a way to work out which way the current is flowing at a given date and time? Thanks Al Quote Link to post Share on other sites
marinheiro 352 Posted April 6, 2021 Share Posted April 6, 2021 1 hour ago, bigal.nz said: Where do you find tide stream data for north cape - or at least a way to work out which way the current is flowing at a given date and time? Thanks Al you could try having a play with this and comparing various locations. https://tides.niwa.co.nz/map need to use the Search function for North Cape or Cape Reinga Quote Link to post Share on other sites
ex TL systems 63 Posted April 6, 2021 Share Posted April 6, 2021 Navionics has tide flow arrows around north cape area. Probably other programs like open cpn as well. Worth looking into. 1 Quote Link to post Share on other sites
bigal.nz 59 Posted April 6, 2021 Author Share Posted April 6, 2021 Yeah that's awesome - found that in the app now too. Thank you, 2.8 Knots seems to be the highest current value I could see predicted in the next few days. Quote Link to post Share on other sites
syohana 37 Posted April 6, 2021 Share Posted April 6, 2021 1 hour ago, bigal.nz said: Yeah that's awesome - found that in the app now too. Thank you, 2.8 Knots seems to be the highest current value I could see predicted in the next few days. That's probably only the tide not the ocean current. You'd need to add the two together to find the total as ocean currents might be significant around Reinga (and amplified by the shallow water, which the forecast model might not include). There are ocean current forecasts available from saildocs.com which you can download as grib files and view using the grib plugin on OpenCPN. You have to really dig into the documentation for saildocs to find how to request the currents forecast but they are very useful for ocean passages. Just be aware that the forecasts are for quite large grid squares so they will give you the general situation that there's a strong east-west current around the cape (for example only, I didn't check) but not the detail of what that does when squeezed into a small shallow area of a few kilometers from land. If in doubt, go right out! (But if you don't have a go, you'll never know ) Quote Link to post Share on other sites
Fish 0 Posted April 6, 2021 Share Posted April 6, 2021 If you want top shelf info, there is Tidetech. Paid service, similar to predictwind. Download grib files etc. I've never used it, but have been on the verge of using it a few times. https://www.tidetechmarinedata.com/metocean-data Quote Link to post Share on other sites
Steve Pope 243 Posted April 7, 2021 Share Posted April 7, 2021 18 hours ago, syohana said: That's probably only the tide not the ocean current. You'd need to add the two together to find the total as ocean currents might be significant around Reinga (and amplified by the shallow water, which the forecast model might not include). There are ocean current forecasts available from saildocs.com which you can download as grib files and view using the grib plugin on OpenCPN. You have to really dig into the documentation for saildocs to find how to request the currents forecast but they are very useful for ocean passages. Just be aware that the forecasts are for quite large grid squares so they will give you the general situation that there's a strong east-west current around the cape (for example only, I didn't check) but not the detail of what that does when squeezed into a small shallow area of a few kilometers from land. If in doubt, go right out! (But if you don't have a go, you'll never know ) I have sat for almost complete tide off Cape maria Van Dieman when heading for North cape, owing to a mis calculation, theoretically doing close to 6 knots through the water but with a across the ground at a speed of 1/2 +- a knot for 2/3 of the tide. Quote Link to post Share on other sites
Addem 95 Posted April 7, 2021 Share Posted April 7, 2021 That would be evil with wind against tide. Quote Link to post Share on other sites
darkside 61 Posted April 7, 2021 Share Posted April 7, 2021 This was track was on a jet boat doing about 6kn. Aiming East no problem, heading down to Spirits Bay and no progress at all. Quote Link to post Share on other sites
bigal.nz 59 Posted April 7, 2021 Author Share Posted April 7, 2021 Guess best to give it a wide berth. 6 knots of current must be when the ocean currents and the tidal stream all come together. Navionics shows the tidal stream never staying in the same direction for long, but on average only peaking at 2-2.5 knots. Quote Link to post Share on other sites
bigal.nz 59 Posted April 8, 2021 Author Share Posted April 8, 2021 Actually worth noting that I am talking about North Cape - not Cape Reinga which looks to be considerably worse. NIWA were happy to help (but it doesn't cover North Cape) Quote Link to post Share on other sites
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