"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