I've read with interest the success Trainers have taking horses from the Nth Island of NZ to the south Island of NZ. There is a general rule that horses from the north are approx 5L + better horses.

Generally trainers travelling to the south wiill win after 2-3 starts.

Maybe its an atmosphere measurement??

No trainer is going to travel on a whim. There must be a motive there. No trainer is going to travel to lose either. Ie bombora has won its last 3 starts. It has gone to rest and most likely have one run before travelling for the Hannnans. Depending on the training methods, horses can get a longer stride which equates to better times.

This is a concept based around some bias that may be generated from training in the north and racing in the south. Nothing to do with trainers methods or preparation