Aviation Weather Routine Thunderstorms

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