There are forecasts available. Ocean
charts show an average position.
If your
chartplotter shows you are moving at a different speed than your
knotmeter, and your
gps heading is at odds with your
compass, you might be in an ocean stream.
Simple answer, it's on some
charts.
In reality, you may want to use it, or cross it as quickly as possible to avoid fighting it.
Get a good navigator. NEVER volunteer to be navigator, it's a thankless job. And you only get respect AFTER the rest of the crew wonders why you said something so early.
Or you went straight to a dark mark, off a strange port..