I can't authenticate it either, but it was posted (/pol) days after the burn-off. It allegedly represents just the wind pattern for those 4 days including the days of burning. The "trail of smoke" includes the vapors before and after the burn and was apparently added to "simulate" where the fallout went during those days. Again, no source was posted as to its creation, but it seems to represent where the wind was blowing during those critical days. It was the closest thing I've yet to find in regard to OPs concern.