[Tossrock]

It's true - the Lyapunov exponent shows that even arbitrarily close points in the system's phase space become separated by exponentially larger distances in time. So even with a computer the size of the universe, you can't really go further than 14 days. I'd highly recommend this Omega Tau podcast episode if you're interested in hearing more about chaos and predictability:

http://omegataupodcast.net/119-chaos/

[moffkalast]

In that case there's probably still room for improvement. Hell, having properly reliable predictions for at least one day ahead in all cases would be stellar.

[selimthegrim]

This is literally one of the defining points of a chaotic system.