A rolling four-week archive of 0.25 degree GFS data is available in s3://noaa-gfs-pds.
Browse the data in your browser at http://awsopendata.s3-website-us-west-2.amazonaws.com/noaa-gfs/
The key layout of data in the buckets is:
Parameter/Vertical Level/YYYYMMDD/HH00/FFF
FFF represents the forecast hour.
The files are in GRIB format. Within each GRIB file are Climate and Forecast v1.6 metedata that describes the data contained.
This Amazon SNS topic publishes a notification for every new object added to the Amazon S3 GFS chunks on AWS. You can subscribe to this Amazon SNS topic using Amazon SQS and AWS Lambda.
arn:aws:sns:us-east-1:104891172899:noaa-gfs-pds
There is a general introdcution to GFS at https://www.ncdc.noaa.gov/data-access/model-data/model-datasets/global-forcast-system-gfs