this would be NOAA in the USA NW Atlantic.
This would be the UK MetOffice.
To the leisure mariner only the prediction for the area he is located is of interest. So if one wanted to could only send the data for the atlantic the meditaranien sea north sea and baltic sea from the inmarsat satelity which covers that area.
Mariners are as every human they use what they are used to. People from the UK us the UK maps. The americans use the NOAA stuff and the germans usually the DWD stuff.
Most of the other countries produce their own weather maps. Would be kind of hard to collect and stream them all.
And redundant since one only needs one good prediction.
The entire forecast time should be broadcasted.
The upper air charts for example are of no particular use so I would not send them.
I have not received my outernet equipment jet so I do not know how the grib resolution is and what data is being sent.
In general you can say that getting some information is better than getting no information.
Right now at sea you can use NAVTEX massages which have some weather information but this is only within 300nm of the coast.
VHF gives some info 30nm of the coats.
Than you have standard SW, AM or FM radio with thair respective ranges.
Inmarsat savetynet gives some weather information. But usually it is of this nature http://tgftp.nws.noaa.gov/data/forecasts/marine/offshore/an/anz935.txt
This is vital stuff in a short format.
So no maps.
qtVlm is the program I use to do weather routing. In a nut shell. I feed it with the grib files and tell it from which point I want to go to which destination. It that calculates the rout which gets me there in the shortest amount of time. This usually means that I do not take the shortest rout because that is usually not the fastest.
ZyGrib is another program I use to what the grib files.
Both programs can overlay analysis maps ( I linked to above) onto the grib data. This way one can compare grib data which is raw computer output with what a real meteorologist has to say about it.
Using all of this and combining it with what I can sea and measure (wind speed, temperature of the air, air pressure and humidity) hight of waves etc gives a prety good understanding of where I am in the weather system and what I have to expect and where I should be going.
Due to the low price of the outernet equipment a huge improvement to the weather information yachtsmen have on rout to their destination can be achieved.
Not in coastal waters but as soon as one leaves more than 30nm offshore right nor moast yachts do not get new weather information.
With outer net this would be possible and could easily save lives.
Feel free to contact me any time if you have further questions.