Bow Wave lift

[[email protected]]

We had 3 flights at Inyokern, CA today with winds from the NNE and all of us had wave like to the east of the Sierra crest.

Folks at Cristal Soaring talk about getting "Bow Wave" with a north wind on the San Gabriel mountains. Perhaps this is what we experienced at IYK.

At the end of the flight, I dropped down closer to the ridge and and it was also working well with some spots of extreme lift and turbulence.

Any thoughts on how this works? Walt - WX?

5Z

[SoaringXCellence]

There is a beautiful example of this in this time-lapse over Tenerife:

http://vimeo.com/23205323

Check it out at 1:18-1:30,also 2:18-2:27 (the rest of the video is stunning too!)

Note the wave structure on either side of the peak.

We get this all the time in Oregon east of Mt. Hood.

[WaltWX[_2_]]

I don't really see a "bow wave" effect in either segment. The first shows the cap cloud down wash off an isolated peak. The second segment shows a lee wave "V" structure downwind of an isolated peak. Really beautiful... though...

Walt Rogers WX

On Saturday, January 24, 2015 at 10:54:10 PM UTC-8, SoaringXCellence wrote:
> There is a beautiful example of this in this time-lapse over Tenerife:
>
> http://vimeo.com/23205323
>
> Check it out at 1:18-1:30,also 2:18-2:27 (the rest of the video is stunning too!)
>
> Note the wave structure on either side of the peak.
>
> We get this all the time in Oregon east of Mt. Hood.

[WaltWX[_2_]]

Well, the fluid dynamics and atmospheric dynamic people have known this for a long time. A Lee Wave occurs when a gravity propagates upwind of a mountain at the same rate as the mean flow. The wave also propagates vertically. Normally the stationary effect is vertical motion downwind of the obstacle to great altitudes. But, there are transient situations when the gravity waves propagates upwind faster than the mean flow, slowly enough, that one gets a fairly persistent "bow wave" effect. All of this is very sensitive to the stability, wind profile and boundary conditions. Explanation of this "Bow Wave" effect involves delving into papers in theoretical fluid dynamics and numerical model simulations. It's even difficult for me to understand clearly.

Bob Sharman NCAR has co-authored some articles on this. M Wurtele wrote some of the intial theoretical papers on Mountain Waves. He was a co-colaborator during the Sierra Wave Project in the 1950s.



Teddi Keller also wrote an interesting paper in 2012: Upstream-Propagating Wave Modes in Moist and Dry Flow over Topography

Sharman and Teddi are married and both work at NCAR. They both got their Ph'd at UCLA from Dr Wurtele. I saw both of them recently at the AMS convention in Phoenix.

Take a look at some of these references if you are into hydrodynamics and atmospheric dynamics:

Scholarly Paper - Lee Waves Ship Waves Sharman Keller
http://scholar.google.com/scholar?q=ship+waves+lee+waves+sharman+keller&btnG=&hl=en&as_sdt=0%2C5&as_vis=1

AMS Journals Online - Ship Waves and Lee Waves
http://journals.ametsoc.org/doi/abs/10.1175/1520-0469(1983)040%3C0396%3ASWALW%3E2.0.CO%3B2

Lee Waves Benign and Malignant
http://www.nasa.gov/centers/dryden/pdf/88288main_H-1890.pdf

NASA Wuertle Sharman 1993

Upstream Propagating Wave Modes in Moist and Dry Flow over Topography TeddieKeller_2012
http://journals.ametsoc.org/doi/pdf/10.1175/JAS-D-12-06.1

RAL | RAL Staff | Robert Sharman
http://www.rap.ucar.edu/staff/sharman-staff.php

The Research Applications Laboratory (RAL)

Teddie Keller | staff.ucar.edu
https://staff.ucar.edu/users/tkeller

[WaltWX[_2_]]

Tom,

My comments on how a "Bow Wave" works with these technical papers really don't help much with trying to understand it. I guess it's another way of saying, "...it falls out of the theory, but we still don't know how to predict it operationally..." Or... "...you find lift, especially wave lift, in the strangest places...take what you get"

Perhaps Teddi Keller or Bob Sharman NCAR might be able to give a more intuitive or practical explanation. Maybe they could give us some tips on which situations we'll find it.

Walt Rogers WX

[Morgan[_2_]]

We pretty regularly get bow waves along coastal headlands. These will show in the marine layer in the spring time when you can see the bulge in front of the headland. Often an accompanying "wake" will stream off downwind and outward from the land with a roll cloud or lenticular of sorts marking it. I have a picture from the satellite that shows this quite clearly in central California. I will have to find and share that. The typical line of the wake is from Pt. Buckhorn to Pt. sal.

Tom, we could hear you from our weak and ratty wave over in Santa Ynez. Slow climbs. Stumbled into a hotspot later in the day with 9kts from 12-18k and then a nice 30 mile run in lift.

Gotta love t-shirt wave in January. Only about -10C at 18.

[Morgan[_2_]]

We pretty regularly get bow waves along coastal headlands. These will show in the marine layer in the spring time when you can see the bulge in front of the headland. Often an accompanying "wake" will stream off downwind and outward from the land with a roll cloud or lenticular of sorts marking it. I have a picture from the satellite that shows this quite clearly in central California. I will have to find and share that. The typical line of the wake is from Pt. Buckhorn to Pt. sal.

Tom, we could hear you from our weak and ratty wave over in Santa Ynez. Slow climbs. Stumbled into a hotspot later in the day with 9kts from 12-18k and then a nice 30 mile run in lift.

Gotta love t-shirt wave in January. Only about -10C at 18.

[Morgan[_2_]]

Here is a photo of a series of bow waves well marked along the points of Central California. Most prominent is Pt. Arguello, just south of Vandenberg AFB. All of the points and headlands were triggering wave on this particular day. I think it was in June about 3 or 4 years ago. We get these waves on a pretty regular basis in the spring. I've even seen a lenticular/roll cloud extend all the way from Buchon to Pt. Sal and then interfere with the bow wave on that next point.

https://plus.google.com/u/0/108472988763833362098/posts/FuSq4bh5owQ?pid=6108741999195665234&oid=108472988763833362098


On Sunday, January 25, 2015 at 9:48:02 PM UTC-8, Morgan wrote:
> We pretty regularly get bow waves along coastal headlands. These will show in the marine layer in the spring time when you can see the bulge in front of the headland. Often an accompanying "wake" will stream off downwind and outward from the land with a roll cloud or lenticular of sorts marking it.. I have a picture from the satellite that shows this quite clearly in central California. I will have to find and share that. The typical line of the wake is from Pt. Buckhorn to Pt. sal.
>
> Tom, we could hear you from our weak and ratty wave over in Santa Ynez. Slow climbs. Stumbled into a hotspot later in the day with 9kts from 12-18k and then a nice 30 mile run in lift.
>
> Gotta love t-shirt wave in January. Only about -10C at 18.