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