Having read the discussion sections for most of the major and some of the minor storms for the past 3 years over at NHC's website.  You get the picture that there are about 5 to 10 computer models that they use almost all the time to predict the path of a storm then they use a few human guesses ( either a mix of the models, or a best guess from the group that have been doing this for years ).  They have in the past, used human guessing to get things right or model's averaged to get things right.  But they admit that they do not know all the factors and repeat a lot of the time that their models are NOT prefect.  

The window of 3 to 6 hours ahead can be shaky at best, and anything longer than that has error factors.  Last season those error factors came to full light, when they could not predict the outcomes of several late season storms and you could tell from reading them there was a massive amount of frustration going on.

The computer models available to them are only as good as the data streams they were designed around.  Things are changing and they know it is happening, but they just can't tell you for sure what and how!!  This makes their job even harder, because so many people now depend on them getting it right, when they the NHC know they can't get it right if the ocean keeps changing and they don't have new modeling programs that predict those changes.

Its like us asking Dave and Stuart to predict the Oil movement in a basin between March 16th at 5 pm and March 18th at 8 pm and tell us where the next blowout will occur before it happens.

Models and programs of a changing world are only so good as the "Past" data used to make them.