Pentrating Towering Cumulus Clouds

Thunderstorm season is up us. I get a little concerned when I see
towering cumulus clouds forming in my flight path because I know that
towering cumulus clouds can turn into thunderstorms.

1. Assuming that thunderstorms were not predicted for the area, is my
concern unjustified?

2. Do most towering cumulus clouds not mature into thunderstorms?

3. Wouldn't large towering cumulus clouds have chartacteristics similar
to thunderstorms (severe turbulence, possible hail, heavy rain, icing)
even if they don't end up becoming an official thunderstorm (lightning
present).

Your advice and experiences would be most appreciated.

-Sami, N2057M Piper Turbo Arrow III

"O. Sami Saydjari" wrote:

Thunderstorm season is up us. I get a little concerned when I see
towering cumulus clouds forming in my flight path because I know that
towering cumulus clouds can turn into thunderstorms.

You are wise to be concerned.

1. Assuming that thunderstorms were not predicted for the area, is my
concern unjustified?

2. Do most towering cumulus clouds not mature into thunderstorms?

Whether a TCU turns into a CB depends on how unstable the atmosphere is and
how much moisture is available. Sometimes the weather guys get it right,
sometimes they don't, but I figure they've got a better chance of getting
it right than I do.

3. Wouldn't large towering cumulus clouds have chartacteristics similar
to thunderstorms (severe turbulence, possible hail, heavy rain, icing)
even if they don't end up becoming an official thunderstorm (lightning
present).

You will certainly find turbulence in TCU, and if you're above the freezing
level, you'll find icing too. I only fly normally aspirated hardware, so I
can't climb high enough to reach the freezing level in the summer. You're
flying a turbo, however, so you might be able to.

Until it turns into a CB, there shouldn't be rain, hail, or lightning.
Flying into a CB is a really bad idea.

In general, I try to avoid flying into TCU. Even around busy airspace like
New York, I find controllers are usually quite accommodating about "request
20 degrees left for weather".

"O. Sami Saydjari" wrote in message
...
Thunderstorm season is up us. I get a little concerned when I see
towering cumulus clouds forming in my flight path because I know that
towering cumulus clouds can turn into thunderstorms.

1. Assuming that thunderstorms were not predicted for the area, is my
concern unjustified?

Whether or nor thunderstorms are predicted should not enter into your
thinking too much. Predictions made in the past are never as good as real
time looking out the window! There may be a change in the lapse rate at
some altitude above the current tops that will keep the TCUs from becoming
CBs or the forecast may be wrong. Only time will tell.

2. Do most towering cumulus clouds not mature into thunderstorms?


Statistically, I don't know but all thunderstorms matured from TCUs. Often
when a CU or TCU becomes dominant, the others around it tend to start
dissipating because the air around the big one is sinking. This is true
when you have airmass type CBs but may not hold for frontal CBs..

3. Wouldn't large towering cumulus clouds have chartacteristics similar to
thunderstorms (severe turbulence, possible hail, heavy rain, icing) even
if they don't end up becoming an official thunderstorm (lightning
present).


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. 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. It takes a rippin' updraft to produce large hail. Any CU,
TCU or CB is going to have icing below 0C and the stronger the updrafts, the
higher the icing is going to extend (it can go to -40C in a CB).

I suspect that you are considering flying into TCUs with tops below 20,000'
and if that is true, you will probably find them like CU clouds only more
so. If you are talking about TCUs over 25,000', you might want to fly
around....:-)


Naturally there is plenty of turbulence in clear air and there are plenty of
smooth rides in nasty looking clouds so YMMV.

Mike
MU-2

-Sami, N2057M Piper Turbo Arrow III

"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.

"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

"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.

"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

"Ron McKinnon" wrote in message
news:J0U8e.1064452$Xk.40112@pd7tw3no...

Thanks. You are right, I have been incorrectly using CB as shorthand for
thunderstorm.

Mike
MU-2
Learning something every day