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#1
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lift on the Sierras?
I fly a motor glider out of the San Francisco Bay Area and frequently
head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: 1. Have others had the same experience as me? If not, where and what time of year? 2. I mostly fly the Sierras from Lake Tahoe down to about Bishop. Do they generate better lift further south? 3. Why are the Sierras so much poorer soaring? I know some of it has to do with the greater moisture content of the vegetation and soil, but have also heard theories about the Pacific's marine influence penetrating that far inland. Are there other theories, or even better, established reasons? Thanks very much. Martin WT |
#2
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lift on the Sierras?
Hellman wrote:
I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: Perhaps what you are seeing is airmass convergence effects. I can't speak about the Sierras, but your description matches clouds we often see in our area. The clouds are clearly formed by, or at least organized by, convergence zones. Some zones are lines, so the clouds form a street; some zones are irregular areas and just a clump of clouds form. Early in the day, the soaring is weak under these "convergence clouds"; later in the day, the soaring is stronger. The original pattern of lines and clumps may change or disappear completely as the thermals strengthen and overwhelm the effect of the valley wind convergences. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4 * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#3
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lift on the Sierras?
Flying up the Sierras from the south, it's usually seemed to me like
things would start to weaken around Mammoth, hence it usually behooves you to cross over to the Whites around Bishop. So I would say yes, they do usually generate better lift to the south. On Sep 8, 10:46*pm, Hellman wrote: I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: 1. Have others had the same experience as me? If not, where and what time of year? 2. I mostly fly the Sierras from Lake Tahoe down to about Bishop. Do they generate better lift further south? 3. Why are the Sierras so much poorer soaring? I know some of it has to do with the greater moisture content of the vegetation and soil, but have also heard theories about the Pacific's marine influence penetrating that far inland. Are there other theories, or even better, established reasons? Thanks very much. Martin WT |
#4
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lift on the Sierras?
On Sep 8, 11:46*pm, Hellman wrote:
I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: 1. Have others had the same experience as me? If not, where and what time of year? 2. I mostly fly the Sierras from Lake Tahoe down to about Bishop. Do they generate better lift further south? 3. Why are the Sierras so much poorer soaring? I know some of it has to do with the greater moisture content of the vegetation and soil, but have also heard theories about the Pacific's marine influence penetrating that far inland. Are there other theories, or even better, established reasons? Thanks very much. Martin WT Martin, I have been down the west side of Lake Tahoe a couple of times this year, pretty close to the crest. I would say that portion is just as good, if not better than the Carson Valley and Pine Nuts. Particularly if the line is clearly on the Sierras. However down toward the Mono-Mineral convergence the lift is always better and more consistent to the East around Patterson and the Swee****er range and typically higher by comparison. I think the lift around Warren and Dana is very good by any standard but the lift is so incredible around the Mono-Mineral convergence that the Sierra gets an somewhat unfavorable comparison. Toward Mammoth the valley influence is what makes that area inconsistent, I believe. Just as it does up north between Lassen and Shasta. Further South I dare not get too deep. SoCal guys can comment more. Sunday there was a good sized cell fairly far west of the crest down west of Coyote Flats. I imagine that part of the Sierra is stronger but higher But in general the Sierra does suffer from either valley influence and/ or marine influence. San Joaquin valley only has lift after frontal passage to setup a decent lapse rate, which otherwise is inverted. Frontal passages however lower cloudbase heights, increases winds in mountainous regions so to have it good in both the SJ valley, and western Seirra and over the Crest seems rare. I am told there once was a soaring operation maybe down by Visalia/Kings area on western Sierra. Might have been hangliders. Those guys would have practical local knowledge of Sierra/Western Sierra flying and when it is best. |
#5
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lift on the Sierras?
On Sep 9, 4:36*pm, wrote:
On Sep 8, 11:46*pm, Hellman wrote: I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: 1. Have others had the same experience as me? If not, where and what time of year? 2. I mostly fly the Sierras from Lake Tahoe down to about Bishop. Do they generate better lift further south? 3. Why are the Sierras so much poorer soaring? I know some of it has to do with the greater moisture content of the vegetation and soil, but have also heard theories about the Pacific's marine influence penetrating that far inland. Are there other theories, or even better, established reasons? Thanks very much. Martin WT Martin, I have been down the west side of Lake Tahoe a couple of times this year, pretty close to the crest. *I would say that portion is just as good, if not better than the Carson Valley and Pine Nuts. Particularly if the line is clearly on the Sierras. *However down toward the Mono-Mineral convergence the lift is always better and more consistent to the East around Patterson and the Swee****er range and typically higher by comparison. *I think the lift around Warren and Dana is very good by any standard but the lift is so incredible around the Mono-Mineral convergence that the Sierra gets an somewhat unfavorable comparison. *Toward Mammoth the valley influence is what makes that area inconsistent, I believe. *Just as it does up north between Lassen and Shasta. Further South I dare not get too deep. *SoCal guys can comment more. Sunday there was a good sized cell fairly far west of the crest down west of Coyote Flats. *I imagine that part of the Sierra is stronger but higher But in general the Sierra does suffer from either valley influence and/ or marine influence. *San Joaquin valley only has lift after frontal passage to setup a decent lapse rate, which otherwise is inverted. Frontal passages however lower cloudbase heights, increases winds in mountainous regions so to have it good in both the SJ valley, and western Seirra and over the Crest seems rare. *I am told there once was a soaring operation maybe down by Visalia/Kings area on western Sierra. *Might have been hangliders. *Those guys would have practical local knowledge of Sierra/Western Sierra flying and when it is best.- Hide quoted text - - Show quoted text - There was an Soaring operation near Pine Flat dam at Wonder Valley dude ranch years ago, I instructed there and it was always difficult to break the inversion to get you high enough to get on the ridge. |
#6
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lift on the Sierras?
On Sep 9, 9:02*pm, "
wrote: On Sep 9, 4:36*pm, wrote: On Sep 8, 11:46*pm, Hellman wrote: I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've occasionally been able to soar on them, but most of the time find them marginal at best. Clouds which would indicate great lift on the mountain ranges to the east (which are more barren and therefore better thermal generators) often have little or no lift under them. There are exceptions and I've had some fantastic times on the Sierras themselvess, but I'm talking about most of the time. Which leads to three questions: 1. Have others had the same experience as me? If not, where and what time of year? 2. I mostly fly the Sierras from Lake Tahoe down to about Bishop. Do they generate better lift further south? 3. Why are the Sierras so much poorer soaring? I know some of it has to do with the greater moisture content of the vegetation and soil, but have also heard theories about the Pacific's marine influence penetrating that far inland. Are there other theories, or even better, established reasons? Thanks very much. Martin WT Martin, I have been down the west side of Lake Tahoe a couple of times this year, pretty close to the crest. *I would say that portion is just as good, if not better than the Carson Valley and Pine Nuts. Particularly if the line is clearly on the Sierras. *However down toward the Mono-Mineral convergence the lift is always better and more consistent to the East around Patterson and the Swee****er range and typically higher by comparison. *I think the lift around Warren and Dana is very good by any standard but the lift is so incredible around the Mono-Mineral convergence that the Sierra gets an somewhat unfavorable comparison. *Toward Mammoth the valley influence is what makes that area inconsistent, I believe. *Just as it does up north between Lassen and Shasta. Further South I dare not get too deep. *SoCal guys can comment more. Sunday there was a good sized cell fairly far west of the crest down west of Coyote Flats. *I imagine that part of the Sierra is stronger but higher But in general the Sierra does suffer from either valley influence and/ or marine influence. *San Joaquin valley only has lift after frontal passage to setup a decent lapse rate, which otherwise is inverted. Frontal passages however lower cloudbase heights, increases winds in mountainous regions so to have it good in both the SJ valley, and western Seirra and over the Crest seems rare. *I am told there once was a soaring operation maybe down by Visalia/Kings area on western Sierra. *Might have been hangliders. *Those guys would have practical local knowledge of Sierra/Western Sierra flying and when it is best.- Hide quoted text - - Show quoted text - There was an Soaring operation near Pine Flat dam at Wonder Valley dude ranch years ago, I instructed there and it was always difficult to break the inversion to get you high enough to get on the ridge.- Hide quoted text - - Show quoted text - There are couple of popular hang gliding sites on the western Sierras foothills, one by Dunlap (Kings area) and one further north by lake McClure. I flew hang gliders at both places and they both have very consistent soaring from spring to fall, but rarely one can get higher then few thousand feet above the hills and make it over the higher terrain. They make it occasionly to Yosemitte valley from lake McClure, so those would be the days we could make it accross. Ramy |
#7
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lift on the Sierras?
On Sep 8, 11:46*pm, Hellman wrote:
I fly a motor glider out of the San Francisco Bay Area and frequently head over the Sierras to the good soaring. My question has to do with lift on the Sierras themselves. I've seen some of your beautiful pictures and stories of your flights - http://www-ee.stanford.edu/~hellman/...ics/020717Yos/ I've made a few flights on the west side of the Sierras down in the south end in a Nimbus 3. The easiest way in a non-motorglider is to get a tow at Tehachapi, get as high as you can there and go north along the "Western Divide". There are quite a few days each year where there will be Cu's along the length of the Western Divide. I made a flight from Tehachapi up to Wishon and Courtright reservoirs with cloudbase at about 13,500. You could fly along just on the west side of the clouds which form along the Western Divide and have pretty much continuous, but not necessarily real strong lift, much like the flight you had over Yosemite where you got the weak wave lift on the West side of the Sierras. I never got into wave-like lift like that on the front side of the cus (it may have been there), but stayed just under the west edge of the cumulus. Most average days when there are cus, the cloud bases are like 13,500 or so, so you are not very high above the terrain under you, which is totally unlandable, so you have to always stay in a position to be able to turn out to the west over the San Joaquin Valley to landable terrain. It's much harder to get up on the Sierras to the Cu's from a normal tow from the San Joaquin Valley side of the Sierras, as Gary says. There is lift, but it is low to the ground, and you have to work up along the ridges, sometimes turning back to the next lower ridge and trying again if you don't make it to a higher level on the first attempt. It's a lot of work grinding around fairly low to the ground over the ridges, staying in position where you have an escape route, and it takes a lot of time to work up to where the Cu's are. I've been able to work up to the clouds on the Western Divide from 2000ft tows out of Reedley and Sequoia airports, working my way up to Dunlop where the hang gliders fly, and from there up into Sequioa Park. A bit further south, I've taken a 2000ft tow at Tulare Airport and worked back to "Blue Ridge" where there is an antenna farm, and then up to the Cu's over Moses Mountain, Homer's Nose and Maggie's Mountan. Again, on the days I did it, the cloud bases were not all that high relative to the terrain, so you could not go very far back into the Sierras and be sure of being able to get back to landable terrain in the valley. From Tulare where I live, you can see a few days each summer where the cloud bases over the Sierras are much higher than average and there is no over-development. Would like to get up there on one of those days, I've always had to be at work. One member of our club, Rick Weiderhold who no longer flies gliders, took a 2000ft tow out of Woodlake near Visalia on one of those spectacular days and worked up to Blue Ridge. From there he eventully made it to Mt. Whitney at "17,999 ft" in a PIK-20 and glided back to Woodlake. As far as I know, he's the only one in our club who's ever done that. There was a story about a European Pilot who, during a contest out of Minden or somewhere up in that area many years ago, flew south along the Sierras and crossed over to the West side and then flew back much to the astonishment of everyone. Anybody remember more about that story? Suspect the conditions on the Western side of the Sierras with the huge high pressure area and the cold ocean water to the west are similar to those on the west side of the Andes. I believe the Andes soaring expedition some years ago that was written up in "Soaring" found it was difficult to climb up into the Andes from the West side and were somewhat disappointed with the types of X-country flights that they were able to make. |
#8
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lift on the Sierras?
Look at OLC traces for this summer, especially Ramy Yanetz, Jim Payne, Marty Eiler and Mark Grubb for thermal routes in the Sierra. You will see different flying styles and routes that reflect varying conditions and pilot preferences. Everything you might want to know can be gleaned from those traces and from XCSkies weather maps, and satellite images from NWS Hanford. I do not know if the WX maps are archived, however. An excellent comparative study can be found on the OLC page for September 6th, 2008. This was the Dust Devil Dash out of Tehachapi and exhibits the spectrum of Sierra flying modes, all on one day and for pilots of widely differing abilities, styles, and aircraft. Several pilots were flying from Minden/Truckee as well. Flights extend from Tehachapi to Alturas. IMO, it was also a fairly representative day for the Sierra in summer. Typically, one chooses between "sheet" thermal / ridge soaring low (sometimes very low) on the east slopes of the Sierra or higher and west of the crest (sometimes significantly far west) in convergence lift. This convergence sets up between the more stable, marine air from the Central Valley on the west and the dry, less stable air of the desert. The Sierra becomes problematic around passes such as the Mammoth / Mono Lake area where the marine air intrudes far into the desert and forms a huge eastward lobe extending from south of Mammoth to near Bridgeport on the north. It can extend as far as Boundary Peak and at times even further east. If you miss this feature (blue thermals or by being braindead), you could be doomed to land in Mammoth, Lee Vining, or Bridgeport as you have penetrated the marine air and lack the height to get to "the only game in town", i.e., the convergence in any direction. Guess how I know... Similar marine air intrusions occur in the Carson Valley due to Lake Tahoe "marine air" intrusion. Sierra thermal flights can be less viable when the ground is extensively covered with snow as is the case in early spring. Finally, I would not generalize by saying that the Whites/Inyo's generally have better lift than the Sierra. In my experience, it varies as a function of time of day (Sierras better early, Whites better later), wind direction and velocity and the nature of the convergence. We commonly fly the Sierra northbound early in the day and the Whites southbound later. There is an old adage that says "the Whites don't work well before 2 P.M.". Not especially true IMO, but they are definitely stronger later and last later in the day than the Sierra in the Owens. My experience suggests that unproductive clouds are more prevalent in the Sierra. Especially at mid and low altitudes, if a cloud is present, the thermal has already passed though your altitude. In the case of shear lines, the lift band can be significantly east of the clouds at lower altitudes as the convergence is wedge shaped and slopes downward in the direction of movement (W -- E in this case). As the convergence slows its advance and ultimately stalls, the clouds become very "moth eaten" in appearance and are not reliable indicators of lift. And then again, I could be totally wrong. Go look at OLC traces, Sat images, and XCSkies maps! |
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