Pentrating Towering Cumulus Clouds

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB clouds.
All three can be thought as different stages of the same think, a cloud
pruduced by convection. Obviously three seconds before a TCU starts
producing lightning and becomes a CB, it is going to a lot like a
thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it is
not the production of lightning that makes it a CB.

It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

Conversely, when a TCU is only slightly taller than a CU, it is going to
be more like a CU inside. There is a relationship between the vertical
height of a convective cloud and turbulence but it is not absolute. I
have never heard of large hail coming from anything other than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB clouds.
All three can be thought as different stages of the same think, a cloud
pruduced by convection. Obviously three seconds before a TCU starts
producing lightning and becomes a CB, it is going to a lot like a
thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it is
not the production of lightning that makes it a CB.


That is what I said ( I think) A thunderstorm becomes a thunderstorm when
the thunder starts. Three seconds before the first lightning, it is still a
TCU.

It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning it
isn't a thunderstorm (CB) so I would say that it is nessesary for a CB to
produce lightning.

Conversely, when a TCU is only slightly taller than a CU, it is going to
be more like a CU inside. There is a relationship between the vertical
height of a convective cloud and turbulence but it is not absolute. I
have never heard of large hail coming from anything other than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),


This is the first time that I have heard that hail defines a thunderstorm.
A thunderstorm is defined by lightning (and therefore thunder). Hail is
produced by updrafts in a cloud through the freezing level allowing frozen
precipitation to remain aloft and grow. I don't see why this couldn't
happen without lightning. I was hailed upon yesterday and there was no
thunder.

Mike
MU-2

"Mike Rapoport" wrote in message
ink.net...

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB clouds.
All three can be thought as different stages of the same think, a cloud
pruduced by convection. Obviously three seconds before a TCU starts
producing lightning and becomes a CB, it is going to a lot like a
thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it
is
not the production of lightning that makes it a CB.


That is what I said ( I think) A thunderstorm becomes a thunderstorm when
the thunder starts. Three seconds before the first lightning, it is still
a TCU.

Well, no. A TCU becomes a cumulo-nimbus when the rounded califlower-like
shape of the TCU begins to top off with a wispy fibrous top, often
stretching downwind like an anvil. This is ice crystals forming at the very
top of the cloud.

That is the classic definition used by weather services. Observers will not
call it a CB if they continue to see the hard-edged form at the tops.... not
until they see the formation of the wispy fibrous top. However, once
lightning, or hail, or funnel-clouds are observed, the observer will almost
surely class it a CB, regardless.



It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning it
isn't a thunderstorm (CB) so I would say that it is nessesary for a CB to
produce lightning.

The production of the ice-crystals at the top will normally be accompanied
by lightning, but ever if it is not, it would still be called a CB if the
fibrous ice-crystal anvil-shaped top exists.



Conversely, when a TCU is only slightly taller than a CU, it is going to
be more like a CU inside. There is a relationship between the vertical
height of a convective cloud and turbulence but it is not absolute. I
have never heard of large hail coming from anything other than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),


This is the first time that I have heard that hail defines a thunderstorm.
A thunderstorm is defined by lightning (and therefore thunder). Hail is
produced by updrafts in a cloud through the freezing level allowing frozen
precipitation to remain aloft and grow. I don't see why this couldn't
happen without lightning. I was hailed upon yesterday and there was no
thunder.


Hail (hard "real" hail, not the soft stuff in some cold-weather cumulus)
.... Hail does not define a thunderstorm, but because the conditions required
for it are typically exactly the same that produce lightning and the rest of
the CB symptoms, you will be hard pressed to find an observer who will not
call a hailing cloud a CB, just because he hasn't seen lightning or heard
thunder.

My general attitude toward TCU is if I could climb above it, then I'll
fly through it. In a 172SP, that means it has to be under about 14,000
feet tall. On long x-countries, I'll generally cruise at 9,000 or
10,000 feet, and have not really encountered anything beyond light to
moderate chop in a cumulus cloud. Generally I'll fly through the ones
that are at most 1,000 - 2,000 feet above me... anything taller, and
I'll request a deviation.

Things definitely get more "interesting" when trying to fly through a
maze of TCUs tho. Without onboard weather scope, I'd say it's safer to
land and wait it out (or if you've got an approach controller who's on
the ball, they may be able to lead you safely through the maze).

"Icebound" wrote in message
...

"Mike Rapoport" wrote in message
ink.net...

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB
clouds. All three can be thought as different stages of the same think,
a cloud pruduced by convection. Obviously three seconds before a TCU
starts producing lightning and becomes a CB, it is going to a lot like
a thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it
is
not the production of lightning that makes it a CB.


That is what I said ( I think) A thunderstorm becomes a thunderstorm
when the thunder starts. Three seconds before the first lightning, it is
still a TCU.

Well, no. A TCU becomes a cumulo-nimbus when the rounded califlower-like
shape of the TCU begins to top off with a wispy fibrous top, often
stretching downwind like an anvil. This is ice crystals forming at the
very top of the cloud.

That is the classic definition used by weather services. Observers will
not call it a CB if they continue to see the hard-edged form at the
tops.... not until they see the formation of the wispy fibrous top.
However, once lightning, or hail, or funnel-clouds are observed, the
observer will almost surely class it a CB, regardless.


Do you have a source of this definition? I can't find one but while
looking, I found several sites with pictures of CBs that don't all have the
wispy tops

Here is one: http://www.chitambo.com/clouds/cloudshtml/calvus.html


It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning
it isn't a thunderstorm (CB) so I would say that it is nessesary for a CB
to produce lightning.

The production of the ice-crystals at the top will normally be accompanied
by lightning, but ever if it is not, it would still be called a CB if the
fibrous ice-crystal anvil-shaped top exists.



Conversely, when a TCU is only slightly taller than a CU, it is going
to be more like a CU inside. There is a relationship between the
vertical height of a convective cloud and turbulence but it is not
absolute. I have never heard of large hail coming from anything other
than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),


This is the first time that I have heard that hail defines a
thunderstorm. A thunderstorm is defined by lightning (and therefore
thunder). Hail is produced by updrafts in a cloud through the freezing
level allowing frozen precipitation to remain aloft and grow. I don't
see why this couldn't happen without lightning. I was hailed upon
yesterday and there was no thunder.


Hail (hard "real" hail, not the soft stuff in some cold-weather cumulus)
... Hail does not define a thunderstorm, but because the conditions
required for it are typically exactly the same that produce lightning and
the rest of the CB symptoms, you will be hard pressed to find an observer
who will not call a hailing cloud a CB, just because he hasn't seen
lightning or heard thunder.



I agree that most observers would call a hailing cloud a CB but the hail
that fell on me yesterday was pea sized and mostly clear yet fell from a
cloud that had a top of perhaps 15,000' and was not producing thunder.

Mike
MU-2

I've tried penetrating a few of these when they were not really high.
The experience was always turbulent.

"Mike Rapoport" wrote in message
link.net...

"Icebound" wrote in message
...

"Mike Rapoport" wrote in message
ink.net...

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB
clouds. All three can be thought as different stages of the same
think, a cloud pruduced by convection. Obviously three seconds before
a TCU starts producing lightning and becomes a CB, it is going to a
lot like a thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it
is
not the production of lightning that makes it a CB.


That is what I said ( I think) A thunderstorm becomes a thunderstorm
when the thunder starts. Three seconds before the first lightning, it
is still a TCU.

Well, no. A TCU becomes a cumulo-nimbus when the rounded califlower-like
shape of the TCU begins to top off with a wispy fibrous top, often
stretching downwind like an anvil. This is ice crystals forming at the
very top of the cloud.

That is the classic definition used by weather services. Observers will
not call it a CB if they continue to see the hard-edged form at the
tops.... not until they see the formation of the wispy fibrous top.
However, once lightning, or hail, or funnel-clouds are observed, the
observer will almost surely class it a CB, regardless.


Do you have a source of this definition? I can't find one but while
looking, I found several sites with pictures of CBs that don't all have
the wispy tops

Here is one: http://www.chitambo.com/clouds/cloudshtml/calvus.html


I chose the definition from the Canadian Manual of Observation which defines
CB:

DEFINITIONS OF CLOUDS
Cumulonimbus: Heavy and dense cloud with
aconsiderable vertical extent, in the form of
amountain or huge tower. At least part of its
upper portion is usually smooth, or fibrous or
striated, and nearly always flattened; this part
often spreads out in the shape of an anvil or vast
plume.

-----

But some more insight can be obtained from the World Met Organization
code-table:
http://badc.nerc.ac.uk/data/surface/code.html (Low cloud type)

Code 3 allows a CB to be defined without the "clearly fibrous" tops, but
which must "at least partially, lack sharp outlines", ....which shows the
the icing of the tops has begun.

Code 9 CB requires the "clearly fibrous" top.

The key is that to meet the classic definition of CB, the icing of the tops
(and hence the smoother fibrous shape)... has at the very least, begun to
form.




It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning
it isn't a thunderstorm (CB) so I would say that it is nessesary for a
CB to produce lightning.

The production of the ice-crystals at the top will normally be
accompanied by lightning, but ever if it is not, it would still be called
a CB if the fibrous ice-crystal anvil-shaped top exists.



Conversely, when a TCU is only slightly taller than a CU, it is going
to be more like a CU inside. There is a relationship between the
vertical height of a convective cloud and turbulence but it is not
absolute. I have never heard of large hail coming from anything other
than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),


This is the first time that I have heard that hail defines a
thunderstorm. A thunderstorm is defined by lightning (and therefore
thunder). Hail is produced by updrafts in a cloud through the freezing
level allowing frozen precipitation to remain aloft and grow. I don't
see why this couldn't happen without lightning. I was hailed upon
yesterday and there was no thunder.


Hail (hard "real" hail, not the soft stuff in some cold-weather cumulus)
... Hail does not define a thunderstorm, but because the conditions
required for it are typically exactly the same that produce lightning and
the rest of the CB symptoms, you will be hard pressed to find an observer
who will not call a hailing cloud a CB, just because he hasn't seen
lightning or heard thunder.



I agree that most observers would call a hailing cloud a CB but the hail
that fell on me yesterday was pea sized and mostly clear yet fell from a
cloud that had a top of perhaps 15,000' and was not producing thunder.


Where, geographically? And did it fall on you on the ground, or did you
encounter it in flight? And how was the cloud top determined.

"Icebound" wrote in message
...

Snip


I chose the definition from the Canadian Manual of Observation which
defines CB:

DEFINITIONS OF CLOUDS
Cumulonimbus: Heavy and dense cloud with
aconsiderable vertical extent, in the form of
amountain or huge tower. At least part of its
upper portion is usually smooth, or fibrous or
striated, and nearly always flattened; this part
often spreads out in the shape of an anvil or vast
plume.

-----

But some more insight can be obtained from the World Met Organization
code-table:
http://badc.nerc.ac.uk/data/surface/code.html (Low cloud type)

Code 3 allows a CB to be defined without the "clearly fibrous" tops, but
which must "at least partially, lack sharp outlines", ....which shows the
the icing of the tops has begun.

Code 9 CB requires the "clearly fibrous" top.

The key is that to meet the classic definition of CB, the icing of the
tops (and hence the smoother fibrous shape)... has at the very least,
begun to form.


Thanks! I have been using "CB" and "thunderstrom" interchangably, perhaps
this is not strictly true.


I agree that most observers would call a hailing cloud a CB but the hail
that fell on me yesterday was pea sized and mostly clear yet fell from a
cloud that had a top of perhaps 15,000' and was not producing thunder.


Where, geographically? And did it fall on you on the ground, or did you
encounter it in flight? And how was the cloud top determined.



North Idaho. I was on the ground (bicycling in hail of all things) The
tops I estimate at 10-12k based on my experience flying in the area (I am
confident that I could easily top them VFR). I gave 15,000' as a very
conservative estimate, I have a high degree of confidence that they were
lower. The highest terrain around is 6200' and this was sticking to the
bottom of the cloud so the vertical height was about 6000'.

Mike
MU-2

"Mike Rapoport" wrote in message
ink.net...

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB clouds.
All three can be thought as different stages of the same think, a cloud
pruduced by convection. Obviously three seconds before a TCU starts
producing lightning and becomes a CB, it is going to a lot like a
thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it
is
not the production of lightning that makes it a CB.

That is what I said ( I think) A thunderstorm becomes a thunderstorm when
the thunder starts. Three seconds before the first lightning, it is still
a TCU.

You are correct that a storm becomes a thunderstorm when thunder
starts (is heard). But a Thunderstorm is not a CB, and a CB is not a
thunderstorm.

A thunderstorm is a 'storm' produced *by* a CB, whereas a CB
is a Cloud. It is not necessary for a cloud to produce lightning/thunder,
in order to be a CB. But it is necessary for the cloud to be a CB
in order to produce lightning/thunder, and it is therefore necessary
for a CB to exist in order for a thunderstorm to exist.

CBs can grow quickly, but it does take time. It is unlikely that three
seconds before the first lightning the cloud was a TCU. It was
probably a CB for a longer-while before the lightning started.

It is not necessary that a CB produce lightning, nor hil, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts. It can
do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning it
isn't a thunderstorm (CB) so I would say that it is nessesary for a CB to
produce lightning.

If it doesn't produce lightning, there isn't a thunderstorm - this
is Correct.

But as noted above, a CB is a type of cloud, not a type of storm. The
cloud can exist without the storm, but the storm cannot occur without
the pre-existance of the cloud. Without thunder/lightning, it can still
be a CB.

Conversely, when a TCU is only slightly taller than a CU, it is going to
be more like a CU inside. There is a relationship between the vertical
height of a convective cloud and turbulence but it is not absolute. I
have never heard of large hail coming from anything other than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while)),

This is the first time that I have heard that hail defines a thunderstorm.
A thunderstorm is defined by lightning (and therefore thunder). Hail is
produced by updrafts in a cloud through the freezing level allowing frozen
precipitation to remain aloft and grow. I don't see why this couldn't
happen without lightning. I was hailed upon yesterday and there was no
thunder.

I did not say that hail defines a thunderstorm. I said that the occurence
of hail proves the existance of a CB. This says nothing, about the
occurence of a thunderstorm.

But note that where I'm saying CB, you're thinking Thunderstorm.
They are not the same thing.

Hail does not define a thunderstorm. Thunder defines a thunderstorm.
An observing station will report the commencement of a thunderstorm
at that station when it hears thunder, and report it done when the thunder
hasn't been heard for fifteen minutes.

The presence or absence of thunder doesn't mean its not raining or
hailing or whatever anymore, nor that the cloud that is producing
these effects has gone away. As you note, hail can certainly occur
without thunder.

The type and nature of the precipitation is a function of the cloud (and
the conditions underlying the creation of that cloud). Though hail does
not define a thunderstorm, the occurrence of hail, by definition, implies
the presence of a CB. Hail comes from CBs, not from TCUs.

Regards

"Icebound" wrote in message
...

"Mike Rapoport" wrote in message
ink.net...

"Ron McKinnon" wrote in message
newscD8e.1052899$8l.772250@pd7tw1no...

"Mike Rapoport" wrote in message
nk.net...

TCU have, as you would expect, characteristics between CU and CB
clouds. All three can be thought as different stages of the same think,
a cloud pruduced by convection. Obviously three seconds before a TCU
starts producing lightning and becomes a CB, it is going to a lot like
a thunderstorm inside.

A minor point: A TCU will not 'produce lightning to become a CB'. If
it produces lightning it *is* a CB, and has been for some time, but it
is
not the production of lightning that makes it a CB.

That is what I said ( I think) A thunderstorm becomes a thunderstorm
when the thunder starts. Three seconds before the first lightning, it is
still a TCU.

Well, no. A TCU becomes a cumulo-nimbus when the rounded califlower-like
shape of the TCU begins to top off with a wispy fibrous top, often
stretching downwind like an anvil. This is ice crystals forming at the
very top of the cloud.

That is the classic definition used by weather services. Observers will
not call it a CB if they continue to see the hard-edged form at the
tops.... not until they see the formation of the wispy fibrous top.
However, once lightning, or hail, or funnel-clouds are observed, the
observer will almost surely class it a CB, regardless.

It is not necessary that a CB produce lightning, nor hail, nor heavy
precipitation, nor Mammae, Funnel Clouds, Tornados or Waterspouts.
It can do none of these things and still be a CB. But if any of these
things happen it is necessarily a CB.

I am not sure what you are saying here, If it doesn't produce lightning
it isn't a thunderstorm (CB) so I would say that it is nessesary for a CB
to produce lightning.

The production of the ice-crystals at the top will normally be accompanied
by lightning, but ever if it is not, it would still be called a CB if the
fibrous ice-crystal anvil-shaped top exists.


Conversely, when a TCU is only slightly taller than a CU, it is going
to be more like a CU inside. There is a relationship between the
vertical height of a convective cloud and turbulence but it is not
absolute. I have never heard of large hail coming from anything other
than a big CB.

If it hails, it's a CB, by definition. A TCU can produce snow
pellets, however (and ice pellets, I think (it's been a while))

This is the first time that I have heard that hail defines a
thunderstorm. A thunderstorm is defined by lightning (and therefore
thunder). Hail is produced by updrafts in a cloud through the freezing
level allowing frozen precipitation to remain aloft and grow. I don't
see why this couldn't happen without lightning. I was hailed upon
yesterday and there was no thunder.

Hail (hard "real" hail, not the soft stuff in some cold-weather cumulus)

the 'soft stuff' -- you're probably talking about snow-pellets, which can
be produced by TCUs (as well as CBs)

... Hail does not define a thunderstorm, but because the conditions
required for it are typically exactly the same that produce lightning and
the rest of the CB symptoms, you will be hard pressed to find an observer
who will not call a hailing cloud a CB, just because he hasn't seen
lightning or heard thunder.

An observer will of course report a hailing cloud as a CB irrespective
of whether thunder or lightning has been observed. But this is because
thunder or lightning are not necessary phenomena for a CB, and it is
necessarily a CB if it produces hail.

Though reporting the clould as a CB, such observer would not report
a thunderstorm, unless he also hears thunder.