Hmmm... interesting. I though maybe they were run at 2 different times... but both are 12Z17Sept.
I posted this a few minutes ago in a different topic and when I went back to see it, it said the topic didn't exist. So since its about models, I'll try again here...
Just a few thoughts on the models, technology, and 5 day forecasts...
The complex equations used by the models have numerous parameters, such as SSTs, pressure, etc. If you run the same model twice, but the second time with just one of these parameters a little different... even out to several decimal places... the outcome will be similar for the first 2 or 3 days, but then it will diverge more and more as time passes. By the time you get out to 5 days you have seen how unpredictable they can be. The technology, while getting better all the time, still is not accurate enough to make the models better out to 5 days. As a simplified example, a temp of 27.4 C could make a huge difference in the output at 5 days than the same model run with a temp of 27.5 C.
If you are a math-type person like me, check out chaos and fractals in the weather. A name to look for is Lorenz, many of these findings came from his work while trying to come up with equations to model the weather.
Also, if you haven't seen them, the animated 5 day forecasts can be interesting to look at.... for Ivan, they are at:
http://www.nhc.noaa.gov/archive/2004/IV ... hics.shtml
You can also animate the 3-day, the strike probability, and the wind swaths.
Jeff