Perma.. You might try asking Carib-weatherman Chris Parker about this and he might also be a good resource to have along on your trip. Try
Chris@mwxc.com . He gets paid a pretty reasonable amount for his forcasts and routing advice but might be willing to at least point you in the direction of the grib.fax archives. You can also visit his personal site at
www.mwxc.com or the caribe weather site
www.caribwx.com or just catch up with him on the
SSB any morning (times and Freq's are on the caribwx site.)