On Friday, August 25, 2017 at 6:11:29 PM UTC-4, wrote:
We see this a lot at Omarama because the cool air from the ocean is being
pushed onto the Southern Alps by the prevailing westerly. This is much denser
than the air east of the divide and this density difference helps make
a hydraulic jump.

Thanks Phillip! I look forward to getting down their one of these days;
hopefully you can show me...
Thanks again, Best Regards, Dave