Archived posting to the Leica Users Group, 2011/12/22
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 > >