Archived posting to the Leica Users Group, 2011/12/22

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Subject: [Leica] Lenticular Clouds
From: jhnichols at lighttube.net (Jim Nichols)
Date: Thu, 22 Dec 2011 22:50:31 -0600
References: <CA+yJO1AT3zFFdxOrNRa8eqHfY1uLs8PMCkkf199bLoWZ_aX2Lg@mail.gmail.com><49E6B130967543998E5C31E1C284605D@jimnichols> <11BA3927-BD0B-4575-B737-11E72EF393A2@bex.net>

Thanks, Howard.  I bow to your more knowledgable explanation.  The only ones 
I recall who might offer more are Dick Butler and the late Dick Johnson.

----- Original Message ----- 
From: "Howard Ritter" <hlritter at bex.net>
To: "Leica Users Group" <lug at leica-users.org>
Sent: Thursday, December 22, 2011 9:44 PM
Subject: Re: [Leica] Lenticular Clouds


> Close, but in this case not a column of rising air.  These particular 
> lenticular clouds are wave clouds, which form when the prevailing airflow 
> undulates downstream for many miles after crossing over a range of hills 
> or mountains. Where the wave ascends into a regime of temperature and 
> pressure such that the air cannot contain all its moisture in vapor form, 
> water condenses out in microscopic droplets and is seen as a cloud. As the 
> wave descends again, conditions once more favor water vapor, and the 
> droplets evaporate and the cloud is gone. So these lenticular clouds are 
> dynamic: like a waterfall, the phenomenon is fixed in place but the 
> substance causing it is in constant flow. There are also static lenticular 
> "caps" that form above some thunderheads at the top, as you say, of a 
> rising column of air, but they're different from the wave type of 
> lenticulars.
>
> The air on the upwind side of a wave cloud is highly favored by sailplane 
> pilots because it is smooth, swift, and rising. One of my most memorable 
> flights was over Vacaville, CA, in the 1970s, when I caught a wave coming 
> off the Napa ridge and found silky-smooth lift at 500 feet per minute or 
> better which I rode for a quarter-hour or so. Not expecting this, and so 
> not dressed for the cool temperatures at altitude, I had to grit my teeth 
> in order to stick with it. But I was determined to reach a personal-best 
> altitude of 10,000 feet, quite thrilling for a student pilot not far past 
> his first solo. I got there, coasted a hundred feet higher for insurance, 
> then popped full spoilers, put the nose down into a redline-speed dive, 
> and scooted as fast as I could for the warm air.
>
> FAA visual-flight rules (VFR)?as well as common sense?prohibit sailplanes 
> from being operated within cloud, so if one is riding a wave that's capped 
> by a lenticular cloud, the ascent, tempting as it may be, has to be 
> terminated before the crest is reached. The rising air beneath a 
> thunderhead capped by a static lenticular is usable only up to the cloud 
> base (except for some hair-raising research flights I've read about!).
>
> ?howard
>
>
> On Dec 22, 2011, at 5:58 PM, Jim Nichols wrote:
>
>> Hi Tina,
>>
>> Sailplane pilots love those cloud shapes, because they mark the top of a 
>> rising column of air, so flying beneath them provides instant lift.
>>
>> Jim Nichols
>> Tullahoma, TN USA
>> ----- Original Message ----- From: "Tina Manley" <images at comporium.net>
>> To: "lug" <lug at leica-users.org>
>> Sent: Thursday, December 22, 2011 4:29 PM
>> Subject: [Leica] Lenticular Clouds
>>
>>
>>> LUG:
>>>
>>> Anybody in England see these clouds?
>>>
>>> http://www.bbc.co.uk/news/uk-england-leeds-16302606
>>>
>>> Pretty spectacular!
>>>
>>> Tina
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information
>
> 




In reply to: Message from images at comporium.net (Tina Manley) ([Leica] Lenticular Clouds)
Message from jhnichols at lighttube.net (Jim Nichols) ([Leica] Lenticular Clouds)
Message from hlritter at bex.net (Howard Ritter) ([Leica] Lenticular Clouds)