There's weather forecasts, and there's real-time weather. When I am in cell range on the east coast, I use the Nexrad weather radar info available on the internet to track T-storm cells. Its very handy to know how strong the cell is and its speed and direction.
When I'm out of cell phone range, I use both grib files downloaded over the SSB from Winlink and the wfax forecasts. I think the grib files are far more detailed, longer range, and generally better the wfax, but gribs seem to consistently underpredict the true wind by 5 knots or more.
With a satphone with data link, you can download both the grib and wfax files--the wfax pictures are much faster and clearer than those over the SSB, but also much more expensive.
Within 60 miles of the US shore, you can usually get the VHF weather, which is at least as good as gribs or wfax.