Where is the next thermal?

Can I agree with Andy. In the UK we often seem to get really strong
thermals close to a large lake or reservoir such as Grafham Water. The
thermals are coming off the surrounding land of course, but the
temperature contrast between the hotter ground and the cooler water seems
to act as a trigger mechanism or a mini front. I have often found that
discontinuities such as the edge of a forest, a ridge line (especially if
pointing into sun), or a ploughed field next to one with crop often seem
to give thermals. Provincial towns and active power stations are also good
ground sources.

However the most reliable thermal markers are circling birds of prey such
as buzzards or kites, or insect eaters such as swallows and swifts.

Derek Copeland


At 22:28 21 September 2009, Andy wrote:
On Sep 21, 1:52=A0pm, danlj wrote:
I hope this turns into a thread on "How I keep going" - there must
be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. These are known as stock ponds in other
places. His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. I hoped he landed out but I don't
think he did.

Andy

On Sep 22, 2:00*am, Derek Copeland wrote:
Can I agree with Andy. In the UK we often seem to get really strong
thermals close to a large lake or reservoir such as Grafham Water. The
thermals are coming off the surrounding land of course, but the
temperature contrast between the hotter ground and the cooler water seems
to act as a trigger mechanism or a mini front. I have often found that
discontinuities such as the edge of a forest, a ridge line (especially if
pointing into sun), or a ploughed field next to one with crop often seem
to give thermals. Provincial towns and active power stations are also good
ground sources.

However the most reliable thermal markers are circling birds of prey such
as buzzards or kites, or insect eaters such as swallows and swifts.

Derek Copeland *

At 22:28 21 September 2009, Andy wrote:

On Sep 21, 1:52=A0pm, danlj *wrote:
I hope this turns into a thread on "How I keep going" - there must
be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. *These are known as stock ponds in other
places. *His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. *I hoped he landed out but I don't
think he did.

Andy

Andy's observation is a secret well-known to cross-country pilots in
Arizona. Sometimes the most ridiculously small and almost dry water
holes will be the source of strong thermals. My theory is that water
holes inject enough moisture into the hot dry air to significantly
increase its buoyancy. We also have small hills consisting of black
volcanic rock that are also good sources. Dry river beds (called
washes in the southwest US) also can be useful sources.

Another issue with clouds here is that on fairly dry days the top of
the lift is often a thousand feet or more below cloud base. However,
a strong thermal will often continue for a short time above the top of
lift fueled by the extra heat released by condensation and eventually
form a cumulus. Once this short thermal pulse has decayed, the area
immediately below the cloud then has no lift, although the original
thermal may still be found a few thousand feet below. I call these
clouds "cumulus decoyus" - decoy cumulus!


Mike

On Sep 22, 11:40*am, Mike the Strike wrote:
On Sep 22, 2:00*am, Derek Copeland wrote:



Can I agree with Andy. In the UK we often seem to get really strong
thermals close to a large lake or reservoir such as Grafham Water. The
thermals are coming off the surrounding land of course, but the
temperature contrast between the hotter ground and the cooler water seems
to act as a trigger mechanism or a mini front. I have often found that
discontinuities such as the edge of a forest, a ridge line (especially if
pointing into sun), or a ploughed field next to one with crop often seem
to give thermals. Provincial towns and active power stations are also good
ground sources.

However the most reliable thermal markers are circling birds of prey such
as buzzards or kites, or insect eaters such as swallows and swifts.

Derek Copeland *

At 22:28 21 September 2009, Andy wrote:

On Sep 21, 1:52=A0pm, danlj *wrote:
I hope this turns into a thread on "How I keep going" - there must
be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. *These are known as stock ponds in other
places. *His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. *I hoped he landed out but I don't
think he did.

Andy

Andy's observation is a secret well-known *to cross-country pilots in
Arizona. *Sometimes the most ridiculously small and almost dry water
holes will be the source of strong thermals. *My theory is that water
holes inject enough moisture into the hot dry air to significantly
increase its buoyancy. *We also have small hills consisting of black
volcanic rock that are also good sources. *Dry river beds (called
washes in the southwest US) also can be useful sources.

Another issue with clouds here is that on fairly dry days the top of
the lift is often a thousand feet or more below cloud base. *However,
a strong thermal will often continue for a short time above the top of
lift fueled by the extra heat released by condensation and eventually
form a cumulus. *Once this short thermal pulse has decayed, the area
immediately below the cloud then has no lift, although the original
thermal may still be found a few thousand feet below. *I call these
clouds "cumulus decoyus" - decoy cumulus!

Mike

Known in other parts of the world as "Cumulus no-liftus"

Craig

On Mon, 21 Sep 2009 15:28:09 -0700 (PDT), Andy
wrote:

On Sep 21, 1:52*pm, danlj wrote:
I hope this turns into a thread on "How I keep going" - there must be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. These are known as stock ponds in other
places. His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. I hoped he landed out but I don't
think he did.

Andy

There was an article in S&G, a few years ago, about thermal origin and
how to guess their location.
It was under the title "Triggers and Feeders". Interesting reading
about the wide areas that collect warmer air, and features on the
ground that induce the bubbles to win adhesion and start soaring.

An antenna, a pond, a building, a moving object etc, all are excellent
triggers, but they're worth nothing without an adequate volume of warm
air being supplied by the feeder area.

Aldo Cernezzi

On Sep 22, 7:03*pm, cernauta wrote:
On Mon, 21 Sep 2009 15:28:09 -0700 (PDT), Andy
wrote:

On Sep 21, 1:52*pm, danlj wrote:
I hope this turns into a thread on "How I keep going" - there must be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. *These are known as stock ponds in other
places. *His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. *I hoped he landed out but I don't
think he did.

Andy

There was an article in S&G, a few years ago, about thermal origin and
how to guess their location.
It was under the title "Triggers and Feeders". Interesting reading
about the wide areas that collect warmer air, and features on the
ground that induce the bubbles to win adhesion and start soaring.

An antenna, a pond, a building, a moving object etc, all are excellent
triggers, but they're worth nothing without an adequate volume of warm
air being supplied by the feeder area.

Aldo Cernezzi

Many times in strong conditions (especially down low) there will a
strong downdraft to be crossed before you hit that (thank you god)
strong thermal.

Bill Snead

I've heard pilots say that the departure of an aircraft will kick off a
thermal from the runway. Worth watching if you are relatively low over
the field and your timing is right to search it out.

At 00:03 23 September 2009, cernauta wrote:
On Mon, 21 Sep 2009 15:28:09 -0700 (PDT), Andy
wrote:

On Sep 21, 1:52*pm, danlj wrote:
I hope this turns into a thread on "How I keep going" - there must
be
scores of pilots more excellent than I who can say more than me.

I well remember that years ago when a visiting German pilot asked for
advice on finding thermals in Arizona I told him to look above and
downwind of cattle tanks. These are known as stock ponds in other
places. His reaction, that I must be a complete idiot for suggesting
that pools of water could trigger thermals, has made me cautious about
offering that advice to anyone. I hoped he landed out but I don't
think he did.

Andy

There was an article in S&G, a few years ago, about thermal origin and
how to guess their location.
It was under the title "Triggers and Feeders". Interesting reading
about the wide areas that collect warmer air, and features on the
ground that induce the bubbles to win adhesion and start soaring.

An antenna, a pond, a building, a moving object etc, all are excellent
triggers, but they're worth nothing without an adequate volume of warm
air being supplied by the feeder area.

Aldo Cernezzi

On Wed, 23 Sep 2009 01:45:02 +0000, Nyal Williams wrote:

I've heard pilots say that the departure of an aircraft will kick off a
thermal from the runway. Worth watching if you are relatively low over
the field and your timing is right to search it out.

Its well known in the free flight model flying world that in the right
conditions a few people running about flapping T-shirts can kick off a
thermal. I once made my own thermal just by running about circle towing
an F1A class competition glider in sparse foot-high dry grass on calm
early morning conditions. It wasn't strong though - just enough to make a
model with a 0.3 m/s min sink speed climb slowly.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

I think this rather depends on the degree of instability in the air. On
relatively stable days the usual thermal sources often don't seem to
work. You need a large area to remain undisturbed for some time until
enough hot air is available to give a decent thermal when triggered. Often
things like towns and motorways don't work because there is too much
trigger activity going on and only tiny weak thermals will form that go to
no great height.

Derek Copeland

At 14:01 23 September 2009, Martin Gregorie wrote:
On Wed, 23 Sep 2009 01:45:02 +0000, Nyal Williams wrote:

I've heard pilots say that the departure of an aircraft will kick off
a
thermal from the runway. Worth watching if you are relatively low
over
the field and your timing is right to search it out.

Its well known in the free flight model flying world that in the right
conditions a few people running about flapping T-shirts can kick off a
thermal. I once made my own thermal just by running about circle towing
an F1A class competition glider in sparse foot-high dry grass on calm
early morning conditions. It wasn't strong though - just enough to make
a
model with a 0.3 m/s min sink speed climb slowly.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Sep 21, 7:09*pm, rlovinggood wrote:
Two items:

1. *Junkyards

2. *Radio transmission antennas.

I can understand the junkyards. *It's a good "discontinuity" in the
surrounding area and has the wrecked cars packed tightly together,
more so than the typical parking lot.

As for the antennas, we speculate it's not the antenna itself, but the
ground they're on. *They are probably most likely on the highest spot
around, even though it all looks quite flat to us. *And, we're talking
about the 2,000' tall, cable stayed antennas and not the little cell
phone towers. *But I guess any water tower and radio antennas are
placed on the highest ground in the local area.

Remember, Your Mileage May Vary...

Ray Lovinggood
Carrboro, North Carolina, USA

Yes, mine varies. I've found those shorter cell phone towers to be
reliable lift points when I'm lower. They act as a wick to dislodge
the warm air from the ground, I think. Reichmann points out that
the warm air at the surface has a surface tension that needs to be
broken. He relates the point by describing a case of finding a
thermal down low that was wicking from a roadside monument.

At medium levels you can sometimes relate a lift source with
its resulting cloud. At a contest a year and a half ago I was
getting lowish (2000ft or so) and was flying over some shaded
ground looking for a thermal. Ahead, I saw a large field in the
sunlight that was being plowed. To my left and even with the
field was a new and growing cu (downwind). I drew a mental line
between the two and pulled up into the strongest thermal of the
day (an honest 8kt climb to cloudbase).

-- Matt

On Sep 23, 1:35*pm, mattm wrote:
On Sep 21, 7:09*pm, rlovinggood wrote:





Two items:

1. *Junkyards

2. *Radio transmission antennas.

I can understand the junkyards. *It's a good "discontinuity" in the
surrounding area and has the wrecked cars packed tightly together,
more so than the typical parking lot.

As for the antennas, we speculate it's not the antenna itself, but the
ground they're on. *They are probably most likely on the highest spot
around, even though it all looks quite flat to us. *And, we're talking
about the 2,000' tall, cable stayed antennas and not the little cell
phone towers. *But I guess any water tower and radio antennas are
placed on the highest ground in the local area.

Remember, Your Mileage May Vary...

Ray Lovinggood
Carrboro, North Carolina, USA

Yes, mine varies. *I've found those shorter cell phone towers to be
reliable lift points when I'm lower. *They act as a wick to dislodge
the warm air from the ground, I think. *Reichmann points out that
the warm air at the surface has a surface tension that needs to be
broken. *He relates the point by describing a case of finding a
thermal down low that was wicking from a roadside monument.

At medium levels you can sometimes relate a lift source with
its resulting cloud. *At a contest a year and a half ago I was
getting lowish (2000ft or so) and was flying over some shaded
ground looking for a thermal. *Ahead, I saw a large field in the
sunlight that was being plowed. *To my left and even with the
field was a new and growing cu (downwind). *I drew a mental line
between the two and pulled up into the strongest thermal of the
day (an honest 8kt climb to cloudbase).

-- Matt

High tension power lines act as triggers, and the dirt roads/gap in
the trees where the towers are located are generators. IMO.

Brad