Hud, has pointed you in the right direction (grib and weather fax).
Since you have the radio
let me narrow that down a bit further - if you can do e-mail with that radio
look at saildocs and viewfax, combined they give you all the weather you could want for free. And you should have them anyway for planning a departure when you have shore internet
If you can't/don't do e-mail aboard then Mscan or Jvcom weatherfax are the answer for you.
Also almost every passage
has a specific HF net you should listen to, as the most accurate weather info you will ever get is from a boat 200 miles up weather from you reporting his actual conditions.