"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