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

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

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

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.

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.

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

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.

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!