Clark they did say they did not move the cone more west due to that so if there was a shift east even in the models it would only be back in line with where the nhc is now.Right now they are on the right of the models and from what i read it was after the storm gets near landfall that they are not buying into not its trek into the gulf

notice there wording

In about 48 hours...Isaac will be nearing
the western portion of the ridge and should move in a general
northwestward heading over the eastern Gulf of Mexico...but large
differences exist between the latest ECMWF and GFS models after
that time.

AFTER the 48 hours in which it is way out in the gulf not the next 48 hours but the time after 48 hours is what they have no faith in.

Just stating fact.Here is the model run http://www.met.sjsu.edu/weather/models/ecmwf-12/ec_sfc6-ani.html and if you look at the end of the run this is what they were talking about not agreeing