Aviation Weather Routine Thunderstorms
For Pilots and Flight Operational Personnel
I want to refresh some concepts regarding this
important issue, so weather is perpetual in the state of the atmosphere.
All flying takes place in the atmosphere, so
flying safe at all time is the key to stay away from incidents and accidents.
Many times you as a Pilot in Command have to
make decisions involving thunderstorms and flying.
This post today looks where and when
thunderstorms occurs most frequently but I just want only to refresh some
safety concepts have you can use as a safety pilot at all time when you are
flying in some tropical and different regions. Thunderstorms occur year around,
in mid-latitudes, so they develop most frequently in spring, summer, and fall.
According in flight pilots are the only means
directly observing cloud tops, icing, and turbulence, therefore no observation
is more timely than one made from the cockpit.
Let’s review, life cycle a thunderstorm cell
during its life cycle progress through three stages:
The cumulus stage, the mature stage, and the
dissipating stage, so it is nearly impossible to visually detect the transition
from one stage to another.
A thunderstorm may be a group of cells in
different stages of the life cycle.
The Cumulus Stage: Most cumulus clouds do not grow
into thunderstorms, every thunderstorms begins as a cumulus. The key future of
the cumulus stage is an updraft; updraft varies in strength and extends from
very near the surface to the cloud top.
Growth rate of the cloud may exceed 3.000 feet
per minute, so it is inadvisable to attempt to climb over rapidly building cumulus
clouds.
During the cumulus stage, water droplets are
quite small but grow to raindrop size as the cloud grows.
The cold rain drags air with it creating a cold
downdraft coexisting with the updraft the cell has reached the mature stage.
The Mature Stage: Precipitation beginning to fall
from the cloud base, so is your signal that a downdraft has developed and a
cell has entered the mature stage.
Cold rain and the downdraft retards compressional
heating, and the downdraft remains cooler than surrounding air.
Therefore, its downward speed is accelerated
and may exceed 2.500 feet per minute.
Meanwhile, updrafts reach a maximum with speeds
possibly exceeding 6.000 feet per minute.
Updrafts and downdrafts in close proximity
create strong vertical shear and a very turbulent environment. All
thunderstorms hazards reach their greatest intensity during the mature stage.
The Dissipating Stage:
Downdrafts describe
the dissipating stage of the thunderstorm cell, so when rain has ended and
downdrafts have decreased the dissipating stage is complete. When all cells of
the thunderstorms have completed this stage, only harmless cloud remnants
remain.
Remember that all individual thunderstorms
measures from less than 5 miles to more than 30 miles in diameter, so the cloud
bases range from a few hundred feet in very moist climates to 10.000 feet or higher
in drier regions.
Tops generally range from 25.000 to 45.000 feet
but rarely extended above 65.000 feet.
Pilots, remember that weather radar detects
only precipitation drops, it does not detect minute cloud droplets, so is to
remember, that hail may fall several miles from the cloud, and hazardous
turbulence may extend as much as 20 miles from the cloud, always try to avoid
the most intense echoes by at least 20 miles that is echoes should be separated
by at least 40 miles before you fly between them.
Also remember this: never regard any thunderstorm
as light, even when radar observes report the echoes are of light intensity.
Avoiding thunderstorms is the best policy: following are some safety issues to
avoid incidents and accidents:
Don’t land or take off in the face of an
approaching thunderstorm. A sudden wind shift or low level turbulence could
cause loss of control.
Don’t attempt to fly under a thunderstorm even
if you can see through to the other side. Turbulence under the storm could be
disastrous.
Don’t try to circumnavigate thunderstorms
covering 6/10 of an area or more either visually or by airborne radar.
Don’t fly without airborne radar into a cloud
mass containing scattered embedded thunderstorms.
Do avoid at least 20 miles any thunderstorm
identified as sever or giving an intense radar echo. This is especially true
under the anvil of a large cumulonimbus.
My best recommendation to all pilots, be safe
at all times during flying close to thunderstorms be a safety pilot and study
and prepare your flight before takeoff study your flight plan your weather
report and review your trip condition
before airborne is the key to be a good pilot and stay away from accidents. Always Fly Safe.
Source: Aviation Weather AC 00-6 A
