I am sure labatt is correct. NAM has a higher resolution that GFS
GFS stands for the Global Forecast System. It is run by National Centers for Environmental Prediction (NCEP) which is a unit of NOAA (National Oceanic and Atmospheric Administration), NWS (National Weather Service), USA. The GFS is run four times per day (00 UTC, 06 UTC, 12 UTC, and 18 UTC) out to 384 hours. Since July 2010 it is run with resolution of 27 km out to 192 hours (previously 35 km) and then with lower resolution for up to hour 384. GFS datafiles that are currently available from NOAA have resolution of 0.5 degree (about 50 km) so this is the real resolution of products that you can see here or on other websites that use the same source. Windguru only uses 180 hours of forecast, because beyond this it's more "crystal gazing" then forecast I think . You see that the model resolution is not that great but it covers the whole Globe!
The North American Mesoscale (NAM) is a regional mesoscale model using enhanced terrain and improved parameterization of surface and precipitation processes. It is also run by NCEP, formerly it's name was Eta, but in early 2005 it was renamed to NAM. Windguru uses 84 hour forecast data in 3 hour step which covers Northern America with average resolution of 0.11 degree (about 12 km). Updates four times per day. Much higher resolution than GFS should give more precise short term forecasts.
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