Hydraulic Jumps?

[Dave Nadler]

Bernard Eckey was a great article in June/July S&G on hydraulic jump.
I've never had the experience of flying in this - anybody here done so?
All the wave flying I've done has been classic wave (primarily ground
induced, but also lots of thermal wave)...

It seems the conditions for this might occur in Colorado?
Sierra lee is mentioned but I've never seen it flying from Minden.

Interested to hear of any experiences with this!

See ya, Dave

[[email protected]]

Interesting, dense air layer usually identified by a roll type cloud.

[Sean Franke]

On Thursday, August 24, 2017 at 4:08:26 PM UTC-7, Dave Nadler wrote:
> Bernard Eckey was a great article in June/July S&G on hydraulic jump.
> I've never had the experience of flying in this - anybody here done so?
> All the wave flying I've done has been classic wave (primarily ground
> induced, but also lots of thermal wave)...
>
> It seems the conditions for this might occur in Colorado?
> Sierra lee is mentioned but I've never seen it flying from Minden.
>
> Interested to hear of any experiences with this!
>
> See ya, Dave

Warner Springs, CA is known for its hydraulic jump.

Sean Franke

[[email protected]]

I am sure you are familiar with Bob Whelan's "Exploring the Monster." about the early wave experiments in the Owens Valley in the 1950's. The Owens and Sierra Nevada wave is a classic example of what a hydraulic jump can offer. 49,000 ft. off of a 14,000 foot mountain range is pretty impressive. (Bob Harris 1986, G-102)

[Tony[_5_]]

Described very well in the fantastic book "Dancing with the Wind" as well

[Tim Taylor]

We tend to get both traditional wave and hydraulic jumps in northern Utah. We also get compression wave in areas where two ranges are close enough to cause interference. I would love to see models that predict some of the dynamic flying we see in the fall through spring. I have had 10 knots straight off a ridgeline to 18,000 feet and other unexpected lift areas.

[Dave Nadler]

On Thursday, August 24, 2017 at 11:08:40 PM UTC-4, Tony wrote:
> Described very well in the fantastic book "Dancing with the Wind" as well

Yes, excerpts are in Bernard's article.

[Dave Nadler]

On Thursday, August 24, 2017 at 9:47:19 PM UTC-4, wrote:
> I am sure you are familiar with Bob Whelan's "Exploring the Monster."
> about the early wave experiments in the Owens Valley in the 1950's.
> The Owens and Sierra Nevada wave is a classic example of what a hydraulic jump
> can offer. 49,000 ft. off of a 14,000 foot mountain range is pretty impressive.
> (Bob Harris 1986, G-102)

Yes, Bob Seyman's classic photo is well known...

But, to my question: Have you ever flown in a hydraulic jump?
Again, all my wave experiences in the Sierra have been classical wave.

[John Cochrane[_3_]]

I got to fly in one in New Zealand, with Gavin in the back. The first sign of the jump was all sorts of excited noise coming from the back seat. Then gradually the picture ahead made sense. Fortunately it was perfectly marked by clouds -- a hill, lenticular cap cloud, gap, then sort of a wall of turbulent cloud. We went to the wall and climbed in smooth wave like conditions in front of it. Really cool.
John Cochrane

[Dave Nadler]

On Friday, August 25, 2017 at 11:13:23 AM UTC-4, John Cochrane wrote:
> I got to fly in one in New Zealand, with Gavin in the back....
>-- a hill, lenticular cap cloud, gap, then sort of a wall of turbulent cloud.

Cool! Did the wall look like the picture in Bernard's article?
What was the discontinuity that provoked the jump?

[[email protected]]

On Saturday, August 26, 2017 at 3:21:05 AM UTC+12, Dave Nadler wrote:
> On Friday, August 25, 2017 at 11:13:23 AM UTC-4, John Cochrane wrote:
> > I got to fly in one in New Zealand, with Gavin in the back....
> >-- a hill, lenticular cap cloud, gap, then sort of a wall of turbulent cloud.
>
> Cool! Did the wall look like the picture in Bernard's article?
> What was the discontinuity that provoked the jump?

The hydraulic jump is more common than most people realise.

Often what is referred to as the 'primary' of the wave is closer to the trigger (back of the hill) than the wavelength of the rest of the wave train. The wave is actually not being triggered by the back of the hill. A hydraulic jump is being triggered on the back of the hill, and the wave train sets up behind the hydraulic jump.

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.

On weak days we often get just the hydraulic jump, no wave train setting up behind. The jump is often very close to the cap cloud, just a few hundred meters downwind of the trailing edge of the cloud. I think this is because the back edge of the best triggers are very steep.

[Dave Nadler]

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

[Dave Nadler]

On Thursday, August 24, 2017 at 7:52:49 PM UTC-4, Sean Franke wrote:
> Warner Springs, CA is known for its hydraulic jump.

Flyable - you've flown it?
What discontinuity causes the jump?
How can you recognize it (vs. classc wave)?

Thanks!
See ya, Dave

PS: Good job at Uvalde!

[[email protected]]

On Friday, August 25, 2017 at 9:18:40 AM UTC-4, Tim Taylor wrote:
> We tend to get both traditional wave and hydraulic jumps in northern Utah.. We also get compression wave in areas where two ranges are close enough to cause interference. I would love to see models that predict some of the dynamic flying we see in the fall through spring. I have had 10 knots straight off a ridgeline to 18,000 feet and other unexpected lift areas.

Compression wave? We have had real wave and low lying rotor here in Michigan which is flat as a pancake. Could this be a compression wave phenomenon? Would love to have some literature reference to read about this! Any references?

Thanks!

[Tim Taylor]

Compression wave is when wave from one ridge ends up intersecting with a downwind ridge. If the wavelength is correct you end up with the downward flow of a primary or secondary flowing into the face of the second ridge. This causes the wave to deflect upward on the face of the second ridge. We have ridges about 15 miles apart and often get a interference from the secondary wave from the first ridge on the face of the second ridge.

[Bruce Hoult]

On Sunday, August 27, 2017 at 7:57:40 PM UTC+3, wrote:
> On Friday, August 25, 2017 at 9:18:40 AM UTC-4, Tim Taylor wrote:
> > We tend to get both traditional wave and hydraulic jumps in northern Utah. We also get compression wave in areas where two ranges are close enough to cause interference. I would love to see models that predict some of the dynamic flying we see in the fall through spring. I have had 10 knots straight off a ridgeline to 18,000 feet and other unexpected lift areas.
>
> Compression wave? We have had real wave and low lying rotor here in Michigan which is flat as a pancake. Could this be a compression wave phenomenon? Would love to have some literature reference to read about this! Any references?

I've read somewhere that in the right conditions (profiles of stability and wind speed with altitude) cumulus cloud streets can trigger wave. Or convergences.