This is some info i had passed onto me about W/T.
If the generating A/C is say an A380-800(HEAVY)
Following A/C----------------Min. Seperation
A380-800---------------------4 nmi
Non-A380-800 Heavy--------6 nmi
Medium-----------------------8 nmi(MTOW of greater than 7,000 kg)
Light--------------------------10 nmi (MTOW of 7,000 kg or less)
Suprising enough there are 3 sections to W/T, all pose a threat.
Immediately behind the wake-generating aircraft is a region of wake turbulence known as the roll-up region,Farther away from the generating aircraft is an area of the wake known as the plateau region, where the vortices have merged and/or attained a nearly constant structure. Even farther downstream from the generating aircraft is a wake area known as the decay region, where substantial diffusion and decay of the vortices occur due to viscous and turbulence effects. At altitude, vortices sink at a rate of 298 to 498 FT per minute and stabilize about 498 to 898 FT below the flight level of the generating aircraft. In some atmospheric condition, they may stay stable but this is only found close to the ground, so you'd most likely experienced Wake Turbulence at the same FL 8nm behind the generating A/C ... even though this isn't a highly likely situation, it was more tha likely the atmospheric conditions aided in keeping the W/T at the same FL and in your path, just a freak situation i guess.
hope this info helps, I know it helped me understand W/T a bit better when it was passed into me.
