Pentrating Towering Cumulus Clouds

"Judah" wrote in message
. ..
"Ron McKinnon" wrote in
newsG%8e.1066820$Xk.925695@pd7tw3no:


"Doug" wrote in message
oups.com...
I was in one once. A towering Cumulus. A big dark one. Weather said
just rain, no thunderstorms. It started raining. Then I lost some
altitude. Looked up and my airplane was coated with ice! Clear, but
ragged ice, about 1/2" thick on all forward facing surfaces.
Fortunately I had warm VMC under me, so I descended and shed the ice.
I don't fly into dark Cumulus clouds anymore. Only reason I did that
time is I was pretty ignorant of weather.

How on earth could you be an Instrument rated Pilot, or even a
non-instrument rated pilot for that matter, and be 'pretty ignorant
of weather' ???

I was just happy to have a
clearance and be able to fly in actual. I was in and out of IMC. Here
comes a big dark one. In I went. Coulda been worse, coulda been
hail....


I suspect that his level of "ignorance of weather" was that he was unable
to accurately predict the conditions inside that dark towering Cumulus
cloud he flew through.

The level of ignorance implied by my post was the level of ignorance
stated by the original poster 'Pretty ignorant about weather", and the
stated actions of that poster

I also suspect that most pilots, VFR or IFR, have been in the
same boat at some point after their IFR training, especially
since it is not a pre-requisite to receiving the instrument rating.
We are mostly taught to depend on forecasts and spend very little
time during training on learning to properly identify cloud formations
from actual pictures or live representations, and to understand what
to expect within each type of cloud.

How can you 'depend on forecasts' alone? They are a sketch of
what someone thinks is *likely* to happen. They are not cast in
concrete statements of what *will* happen everywhere in the given
area. And even if they're right-on, for the most part, they can still
miss very localized or short-term events. You can't rely on the
forecasts alone.

And, in any case, you need to know enough about weather to
understand the forecasts so that you know how they might impact
you. This implies a certain understanding of the characteristics
of things like clouds.

During VFR training, you learn to just stay away from them.
And during IFR training, you get pounded about the extremes
(CBs and Stratus clouds) but there is really inadequate training
of the stuff in the middle - probably because the stuff in
the middle varies so widely.

If you know that you should stay the hell away from CBs, you
should know to stay away from "big, dark, TCUs" as well.
A big, dark, TCU, depending on how big and dark it is, for
your intents and purposes, should be considered the same
as a CB. A cloud doesn't just turn into a CB and becoume
dangerous because now it's a CB; it becomes dangerous the
bigger it gets. A big, dark TCU, should probably be considered
as dangerous as a new CB.

Can you accurately predict conditions inside of a towering CU
unless you get inside of it? There are different conditions even
within the same cloud that depend on many factors tat include
pressure, elapsed time, wind speed, humidity levels, etc. So
while one dark TCU may produce hail, rain, and ice, the next
dark TCU might be fairly uneventful and produce some
turbulence as you enter and exit and that's all.

You don't need to know what a grizzly bear had for breakfast
to know not to poke him with a stick. Respect him just 'cause
he's a grizzly bear.

'Accuracy of predictions' is a red-herring, here. Accurate
predictions of conditions inside a TCU are not required.
Just know that if they're big and dark, they're probably nasty.
If you wouldn't penetrate or fly in the vicinity of a CB, you
should probably accord a 'big dark TCU' similar respect.

I think most people are fairly ignorant of weather, even if we
think we are experts. Otherwise the meteorologists would
never be wrong, and the rest of us COULD just depend on the
forecasts...

I suggest that meteorologists are not absolutely wrong as much
as you think. Or as much wrong as you think. But even so, this
does not speak to ignorance of weather, nor or weather processes,
but more to the difficulty in predicting very far into the future the
behaviour of a largely chaotic system such as the atmosphere.

Pilots do not need to be degreed meteorologists, but they do
need to know enough to understand what meteorologists are
telling them, and they do need to know the *basics* well enough
to expect that flying into a 'big, dark TCU' is very likely a
problem.

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".

"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 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

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

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).

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

"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.


I get concerned too. So I stay away from them and out of them. My choice
is to not take the chance and get beat around inside. If it's towering it's
likely got
some fair updrafts in there. It's about personal minimums and sticking to
them.