12Z GFS starts by not quite going as far south, but a bit further west, stays north of the Caribbean islands (but still very close) by Thursday it's north of Puerto Rico, but slightly west of the earlier run, so Irma is forecast to move a bit faster.

By Midday thursday it's slightly southwest of the prior run, and midday thursday it's very close to the Central Bahamas as a cat 4/5. (40nm sw of the earlier run) Saturday morning it's over the northern part of Cat island in the Bahamas

Then over Great Abaco as a cat 4/5 on Sunday (Sep 10th) where it starts to head north.