Let us not get overly obsessed with real time data (where's the funding for that?) and on
line availability. The nature of the beast is that the tide and current tables are accurate as far as they go. But a couple of days of 20 kt plus on shore winds is going to effect them and you're going to have to know how it will.
It is best to treat such tables as good estimates, subject to a lot of variables. Otherwise you might find yourself declaring the tide on the ebb, only to have your AB seaman flick a butt over the side and proclaim, "looks like she's floodin' to me, mate."