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

When in doubt, don't! The CU's wouldn't be towering if they did not contain
strong updrafts...and don't forget the strong downdrafts on the outside of
the "tower." I can remember being rolled 60 degrees one day when I decided
to fly close to, but not into, such a cloud. Depending on penetration
altitude versus freezing level, they also contain what I call "splat icing,"
which can coat your airplane with a glossy load in a few seconds...look for
that (or please, don't look for that) in the top one-third of the cloud.

Bottom line: Stay away. Might not be anything in there, but I'm no one to
take chances.

Bob Gardner

"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?

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.

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

No, one is always justified in being concerned about thunderstorms, or
more specifically, being concerned about avoiding them.


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

Yes, very few make it to a full-blown thunderstorm. Part of it depends
on your definition of towering. To me a 6,000 foot tall clouds is
towering, but if you mean 50,000 feet, then few probably get that high
without becoming a thunderstorm.


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).

I can't say for sure, but I don't think you'd have most of the agove
without also having thunder and lightning.


Your advice and experiences would be most appreciated.

I've flown through many cumulus clouds that were 10-15,000 feet tall.
It is great fun, but can be a lot of work when IFR as it is hard to
maintain altitude and airspeed in some of the larger clouds. It isn't
unusual to gain or lose 500' while transiting a larger cloud.


Matt

"Matt Whiting" wrote in message
...
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.

....snip...

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

Yes, very few make it to a full-blown thunderstorm. Part of it depends on
your definition of towering. To me a 6,000 foot tall clouds is towering,
but if you mean 50,000 feet, then few probably get that high without
becoming a thunderstorm.

..... "...if you mean 50,000 feet....", then probably ALL will be a
thunderstorm. Few clouds-of-vertical-development will exceed 30,000 feet
ASL without characteristics of a "thunderstorm".

If a cu has penetrated the freezing level, that's enough to scare me. We get
some dandies over the Cascades, Siskiyous, and Rockies.

Bob Gardner

"Icebound" wrote in message
...

"Matt Whiting" wrote in message
...
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.

...snip...

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

Yes, very few make it to a full-blown thunderstorm. Part of it depends
on your definition of towering. To me a 6,000 foot tall clouds is
towering, but if you mean 50,000 feet, then few probably get that high
without becoming a thunderstorm.

.... "...if you mean 50,000 feet....", then probably ALL will be a
thunderstorm. Few clouds-of-vertical-development will exceed 30,000 feet
ASL without characteristics of a "thunderstorm".

"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?


It would help if, before you go, you try to get enough information about the
overall weather situation. You may be able to make a guess as to why the
forecast was what it was. Was there a serious area of thunderstorms
forecast to be to the south of you which may now have moved a little further
north than expected.... Or is there a high-pressure-system coming from the
west, and the forecasters thought it would suppress the serious development?

In the first situation, I would be extremely concerned that thunderstorms
were immenently probable. In the second, well... I would be more
comfortable with a wait-and-see... so the high-pressure-system hasn't
suppressed activity as much as they thought, but it is much less likely that
anything really serious is going to develop.


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


There are many factors that may encourage or suppress the vertical growth.
What is causing the lift, and is it strong and persistant, or weak and
temporary? Is the low-level atmosphere becoming hotter and more humid or
cooler and drier? Is the upper atmosphere under a cyclonic or anticyclonic
influence, etc... You defer to the judgement of the meteorologists, but in
some cases your own assessment of the *overall* weather situation may help
you confirm or question their judgement. In many cases obvious answers are
not available even to them.

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).


Towering Cumulus are but a stage on the way to development to thunderstorms.
Therefore you already have strong vertical currents, and large amounts of
condensed water. Most of it is still going upwards, but the result on the
windshield and engine-air-intake can be the same as a rainstorm. Some of it
could already be frozen... precursor to hail, only its not falling yet.
Turbulence, and (above the freezing level) icing.

Your advice and experiences would be most appreciated.

-Sami, N2057M Piper Turbo Arrow III

"Bob Gardner" wrote in message
...
If a cu has penetrated the freezing level, that's enough to scare me. We
get some dandies over the Cascades, Siskiyous, and Rockies.


Generally a cloud that penetrates minus-10 Celsius will produce
precipitation. But in cold weather it may do that in 4000 feet and be a
rather benign shower. When the cloud develops vertically through 25, 35, or
especially 45 thousand feet, however.... that's when it gets exciting.

O. Sami Saydjari wrote:

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

I once flew into a towering cumulus in a C172 and had some interesting
things happen. I was on an IFR training flight and had been solid IMC
for about a half hour when we popped out to spot the most beautiful
towering white monster dead in our path that shot straight up to about
20k. It was clear blue all around except for the TC.

I asked my CFII if this was a problem and if I should ask for other
routing. He seemed unconcerned and so we proceeded directly into it.
I didn't question him because, after all, I was a lowly IFR student( an
attitude that I have thoroughly revamped ) and he had some 5000 hours of
flying on the logs.

The first thing that happened was a strong downdraft that pegged the
VSI, followed by small hail hitting us that sounded like the airplane
was being "sandpapered". We went through some wild oscillations of yaw
and 200-300 ft altitude excursions. The yoke required full right and
left deflection at times to keep upright and the seat belts cut into us
enough at times to be noticeable.

Then, I felt a static charge all over my arms ( the hairs actually rose
up!) that seemed to build followed by most of the instruments going TU.
The only instrument that seemed stable enough to be usable was my little
hand held GPS which allowed me to keep the aircraft level by watching
the GPS compass card.

We exited as suddenly as we entered into calm blue sky. The contrast was
actually kind of eerie!

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).

Yes, would be my answer.

Antonio