Mountain Wave Activity in the Magaliesberg

[John.com]

This was posted by me on AVCOM, so forgive me for repeating it for my MLer pilot friends!

At around 06.30 on Thursday morning there was MOUNTAIN WAVE ACTIVITY (estimated at 6,500 - 7,500ft) in place 8 miles north of Lanseria (FALA), along the Kalkheuwel Ridge line, as shown in the Google Earth image, along with the point of photography (red arrow). AD shown is FALA. Winds aloft were NNE 20-25 knots.

The large cloud on the left in the second image was overhead the 'sugarloaf' mountain, Renosterkop, just to the SW of Pelindaba.

This is of particular interest as the winds aloft were not that high and, as we know, the Magaliesberg and the parallel ridges are not deemed significant mountains.

So this is what to look out for as a little rock and roll would be expected with the updrafts and downdrafts associated with the mountain wave phenomenon!

[nicow]

Interesting...Thanks for sharing .

[cobra]

Thanks John

interesting reading from the net...

Mountain wave safety

* Altitude 50% above the terrain - if surrounding terrain is 5,000 feet and the mountain top is 7,000 feet, use 1/2 of the 2000-foot value and fly 1000 feet above the mountain top.
* Approach at a 45-degree angle - The rule-of-thumb of flying half again as high as the mountain is designed to reduce the risk of entering the turbulent rotor zone, but it does not necessarily give you a sufficient margin to allow for height loss due to downdrafts. You must have an escape route.
* Avoid ragged or irregular-shaped lenticulars can contain the same turbulence as the rotor area.
* Climb in lift or dive in sink - by diving in sink, rather than trying to maintain altitude, the airplane is exposed to the effects of the downdraft for a lesser amount of time. Even though the rate of descent will likely be double or more the rate of climbing at the best rate-of-climb airspeed, the airplane will loose less altitude overall. (if you have the height !)
* Avoid the rotor - If rotor clouds are not present, visualize the area of the rotor and avoid it.
* Visualize the wave length - When flying parallel to the wave, fly in the updraft area.

The clouds above looks like ordinary Strato-Cumulus to me or it could be Cap Cloud formed by waves

video of lenticulars mountain waves

http://footage.shutterstock.com/clip-36 ... louds.html

[nicow]

Thanks John

interesting reading from the net...

Mountain wave safety

* Altitude 50% above the terrain - if surrounding terrain is 5,000 feet and the mountain top is 7,000 feet, use 1/2 of the 2000-foot value and fly 1000 feet above the mountain top.
* Approach at a 45-degree angle - The rule-of-thumb of flying half again as high as the mountain is designed to reduce the risk of entering the turbulent rotor zone, but it does not necessarily give you a sufficient margin to allow for height loss due to downdrafts. You must have an escape route.
* Avoid ragged or irregular-shaped lenticulars can contain the same turbulence as the rotor area.
* Climb in lift or dive in sink - by diving in sink, rather than trying to maintain altitude, the airplane is exposed to the effects of the downdraft for a lesser amount of time. Even though the rate of descent will likely be double or more the rate of climbing at the best rate-of-climb airspeed, the airplane will loose less altitude overall. (if you have the height !)
* Avoid the rotor - If rotor clouds are not present, visualize the area of the rotor and avoid it.
* Visualize the wave length - When flying parallel to the wave, fly in the updraft area.

The clouds above looks like ordinary Strato-Cumulus to me or it could be Cap Cloud formed by waves

video of lenticulars mountain waves

http://footage.shutterstock.com/clip-36 ... louds.html

Thanks

[Turbo]

in situations like this i wish i was a bird -- they know so much about weather!!