Caribbean tidal query

[2greens1red]

Planning a passage north of Grenada, to estimate tide we used the Tidal Diamond and table on the relevant Imray chart (based on H/water Georgetown).

The result was exactly 180° reciprocal from that given on our Navionics software.

Imray base their info on UK Admiralty data. Navionics declined to give us their data source.

We had converted all times to local.

Could anyone offer an explanation?

[atoll]

it might have to do with the strong(1-2kts) permanent west going current that runs along the south American coast this would negate the small tidal current of the caribbean sea.

possibly with imray showing inshore flow,and navionics showing offshore flow

[2greens1red]

Many thanks, Atoll - that makes sense, and just shows up my inexperience.

My level is basic Day Skipper, and ocean currents are a whole new ballgame, and hasn't been mentioned in my training so far; hasn't appeared in the Yachtmaster text books I've been reading either.

I appreciate the lead to further study!

[monte]

Take a look in the Caribbean compass. There is a good tides article by don street that explains the tides around the islands. It's a pity I was just shown it yesterday as it would have made our trip from BVIs up current to antigua make a bit more sense. Basically the tides run toward the moon, worst at full moon (which we just had) and would have explained why we had 3K current against us!

[belizesailor]

My Ocean (www.myocean.eu) consolidates lots of data including current data. Some GRIB viewers support direct downloads from them...such as SailGRIB which I have.

[belizesailor]

Display below based on the MyOcean data for the Grenada area.

[belizesailor]

Originally Posted by atoll

it might have to do with the strong(1-2kts) permanent west going current that runs along the south American coast this would negate the small tidal current of the caribbean sea.

possibly with imray showing inshore flow,and navionics showing offshore flow

Yes, the current flow due to tidal variance is going to be very small compared to the significant open ocean current that transits the area. True most anywhere in the Carib except where hydrographic features enhance tidal current...Bahamas being a dramatic example.