Weather charts are created by NOAA and broadcast via radiofax by USCG, and can be received with Airmail software using any of the SCS Pactor modems.
The first thing you need is the broadcast schedule. So go to this web page: http://weather.noaa.gov/fax/marine.shtml Scroll down and find “Worldwide Marine Radiofacsimile Broadcast Schedules (PDF)” and download a copy. There are five US broadcast stations: Pt. Reyes (near San Francisco), New Oreans, Boston, Alaska and Hawaii, plus a bunch of overseas stations. The US stations are coast guard and quite reliable, the others vary. The schedule tells you times for each chart, for each station.
Now open Airmail, open the “fax” window (“Get Fax” under Modules menu, or button on toolbar). With radio and modem powered on, select fax mode, select station and frequency. The radio freq should be set (selected freq minus 1.9 khz), and you should hear a characteristic “warbling” fax tone, if the station is transmitting. Try each frequency for the clearest signal. Then wait– Airmail will detect the special tone at the beginning and end of each fax transmission, copes each chart and saves them automatically.
You will note in the schedule that the charts are send in blocks over a couple of hour period, just turn the radio on and open’s airmail’s fax window, and let it run during that period.
Now, all that said, you can get most of the same information from GFS grib data. The zero-hour forecast-time is based on actual conditions, then each forecast is computed from that. The same data is used for grib files, and also to generate the fax charts. The fax charts are reviewed by forecasters, and information added– storm warnings, frontal positions, etc.