'When the modifier represents new information to the hearers, it is more likely to occur postnominally' (M&M 1999:92). The order seems also to depend on the type of noun (a mass noun, etc. ), see Morse & Maxwell (1999:128).
Morse & Maxwell 1999:91
Legal Values and Meanings:
both orders with neither order dominant
both but for specific forms
both but depend on the characteristics of the nominal head