Meet Mr. Lenticular!!

Dave Siciliano

Dave Siciliano

Final Approach
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Feb 27, 2005
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Dave Siciliano
Friend that flies for NW shot this the other day. :eek:
 

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Is that Mt. Rainier?

--Kath
 
Dave Siciliano said:
Friend that flies for NW shot this the other day. :eek:
Click to expand...

hey dave, nice pic!

is that a true lenticular or just a "cap cloud"?

lenticular clouds are associated with a standing wave phenomenon which occurs when strong winds blow at (close to) right angles to a mountain ridge. they typically appear in ascending layers over the ridge line:

http://en.wikipedia.org/wiki/Lenticular_cloud


cap clouds are also associated with mountains, but not the standing wave phenom. they are produced when the air is orographically lifted upslope and condenses into a cloud which "caps" the peak or ridge:

Orographic clouds, as the name implies, are produced by the flow of air interacting with mountainous terrain.
  • Cap clouds form when air containing water vapor is uplifted on the windward slide of the slope and reaches saturation producing liquid water cloud droplets and a cloud which can "cap" the summit. The spectacular picture was provided by Michael Nahmias and shows the cap cloud shrouded summit of Mt. Ranier.
  • Lenticular clouds are lens-shaped clouds that can result from strong wind flow over rugged terrain. At the time of this photo, the winds were blowing around 30-40 mph from right to left, forming several lenticular clouds. Sometimes they stack up like pancakes in multiple layers as are several depicted in this first photo. The strong flow produces a distinct up and down wavelike pattern on the lee side of the mountain or large hill and the lenticular clouds tend to form at the peaks of these waves. They sometimes are very round and the edges are so well defined that they resemble flying saucers. This close up sequence shows a large lenticular cloud at various stages of illumination as the sun moved lower on the horizon and lit the cloud from below. Another lenticular cloud can be seen in the background of the last frame of the sequence. Lenticular clouds are often placed into the middle cloud category since they are most common at those altitudes. PSC meteorology graduate, Jay Shafer, has also provided some stunning additional lenticular pictures taken around the White Mountain region of New Hampshire.
still a nice picture. thank your buddy for us!
 
Vic:

Very nice of you to point this out. My captain friend from NW called it lenticular and I passed that along. You're correct, I don't see the rolling motion associated with those. The winds were very strong at the time and my friend may have assumed it would be nasty in there. He's pretty sophisticated when it comes to weather; let me ask him what he was thinking.

Dave
 
Dave Siciliano said:
Friend that flies for NW shot this the other day. :eek:
Click to expand...

Dave, I'm pretty sure the pictured cloud isn't a standing lenticular. On the other hand, the cloud in the attached picture is definitely a standing lenticlur (Tetons, west of Jackson Hole, WY).
 

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Dave Siciliano said:
Vic:

Very nice of you to point this out. My captain friend from NW called it lenticular and I passed that along. You're correct, I don't see the rolling motion associated with those. The winds were very strong at the time and my friend may have assumed it would be nasty in there. He's pretty sophisticated when it comes to weather; let me ask him what he was thinking.

Dave
Click to expand...

hey dave!

i'm sure your buddy was correct either way: it would've been VERY rough anywhere near/downwind of that ridge on that day!

i've been downwind at low altitude in the rotor of a standing wave (mojave, ca.) and it's not fun, 'specially at night! (what can i say, i was low time and inexperienced :hairraise: ). good old stinson just chugged along and got me home. i love that old airplane. :yes:
 
scottd said:
Dave,

Based on the other clouds in the image and the perspective with the mountain, the altitude looks like somewhere between 10-15K. You wouldn't see this kind of stratrocumulus field (below the aircraft) at FL350.
Click to expand...

Thanks Scott; I emailed my friend; I'm sure he'll tell us what was going on if he recalls where he was when he took the pic. He took several; I just passed this one along.

Dave
 
Here's Al's response.
Dave,

Yea – Cap cloud would be more like it. Guessing we were out of 12,000’ or so. I know it was above 10K, since we were done with the Climb Check.


Boy! Y'all are tough. This was just a casual e-mail from a friend with a pic. YOU SURE STRAIGHTENED HIM OUT! :rofl:

Glad y'all are so nice; think of what would have happened on that other board. :hairraise:
 
Fascinating stuff Scott!! Thanks for sharing this info, may keep me out of trouble sometime!!

Dave
 
scottd said:
I got caught in a wave just east of the Appalachians while at 8000 feet. I lost 800 feet over a two minute period at full power in my Turbo Arrow IV.
Click to expand...

I got one of those last year near Pulaski VOR in Virginia. West winds at about 50kts at our altitude, got into some pretty bad turb. Hit one spot where we were in full power Vy climb, and the VSI stayed at -500fpm, lost 1500ft in three minutes, then broke out. There were standing lennies just north of our destination.
 
Dave: Thanks for the post!! Vic and Scott! Thanks for some excellent discussion on the topic! Very informative. I have only ever seen a lenticular while flying over it commercial while crossing the rockies.
 
hey scott!

wow! very cool movie! thanks for the in-depth discussion.

i sure do like the Blue Board!
 
scottd said:
Bob,

In some cases, these waves can and do penetrate very high into the flight levels even up to FL450.
Click to expand...

Yes they do. In fact the current world altitude record for gliders is right around there. Wave has been observed at heights up to FL600 in New Zealand, which is why Steve Fawcett (sp?) is on board project Perlan to break it. It takes big bucks to go that high, because you need astronaut pressure suits and lots of oxygen. Also need to practically be on call for about 10 years for the one day that conditions are right.

Of course these guys run into the same problems as U2 pilots at those high altitudes where there is a very small difference between your flutter speed and stall speed. I can imagine it gets pretty scary when the craft starts shaking and you don't know if its flutter or stall. Fascinating stuff, though.
 
Dave Siciliano said:
The winds were very strong at the time and my friend may have assumed it would be nasty in there.
Click to expand...
Heck, yeah, it would be nasty in there! There's a doggone MOUNTAIN inside that thing!! :eek:!!

;)
 
Attached pic shows Mt. Fuji, yesterday. (provided the attachment works).

Found it on the ABC News website today.
 

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