Cumulus Clouds - Tthe Good, the Bad, and the Ugly
Clouds provide us a clear indication of what is happening in the air above us. Cumulus clouds are the result of vertical air movement. The FAA calls them heaped or piled. Normal people call them marshmallow. We will call them Cumulus.
Dennis PAGEN, expert in micrometeorology and Sport Pilot weather said, “A cumulus cloud is the top of a thermal updraft”. This is true and will be the basis to our flight adventure today.
The concept is not to be scared of any cumulus that pops in the sky, but to know what type of air you will be entering based on the shape of the cumulus cloud. As we know from the weather to fly system, moisture and clouds can form their own weather.
The Good
Lets start with the good. The cumulus clouds that provide some texture to the skies, provide us enough bumps for moderate turbulence, and provide us flying conditions that will not bring us any bad or ugly stories.
Simply, the good cumulus are wider than they are tall. We know and see these all the time. It looks like a nice day. The cumulus are there but not that tall. You read the upper air tables and the air cools the typical 2 degrees C per 1000 feet altitude increase.
If you are used to flying in perfectly smooth air you may even be scary flying with nice looking cumulus in the skies. If you are an experienced instructor, you tell your student “these bumps are normal. This is typical for this type of flight”. You are not scared, but you are on your toes because the air is moving up or down and it is a significant factor in your flight.
The Bad
We move to the bad. This is where the thermals are stronger, the air is going up faster and down faster. This is where you start to wonder. You read the upper air tables and the air cools from 2 to 3 degrees C per 1000 feet altitude increase.
It is simply when the Cumulus clouds are as tall as they are wide. This could be considered an average nice day by the normal person walking on the street and looking up in the sky. Afternoon clouds predicted and a slight chance of a thunderstorm. If you decide to fly on an unstable day and fly in the late morning this will effect you.
This is the medium to severe bump tolerance zone. It is bad but it is not ugly. You maintain positive control of the aircraft most of the time but there are definite altitude and attitude changes as you fly though the bumps. This is where the flight instructor informs the student that this is normal but it will be bumpy. This is where the instructor is on his toes and must provide active control near the ground. Things could go bad if you are not experienced or you depend on a student to account for a down draft near the ground.
The UGLY
We now address the ugly cumulus. This is where the clouds look pretty, but the air is ugly. This is where most of us hope not to ever be, and we can plan on not being there. The cumulus clouds are taller than they are wide. The day starts of very nice and forgiving, but can go bad fast and get past any light sport aircraft limitations quickly. You can tell if it is going to this type of a day from the upper air charts with the air cooling from 3 to 4 degrees C per 1000 feet, or the weather people predicting there are going to be thunderstorms in the afternoon. If you have to simply watch the skies, you will see bad looking cumulus early in the day as discussed above, or medium cumulus clouds very early in the day.
Ugly air means lack of control and a good chance of a bad landing. Ugly can be avoided through using the basic "weather to fly" concepts.
Keep in Mind
1. Cumulus clouds are formed from enough moisture in the air rising and condensing, but if the air is dry and the sky blue you can still have the thermals with no clouds.2. Ugly air cumulus can also be bad looking cumulus with higher wind looking tops. This is where you combine bad looking cumulus with wind creating the ugly situation.
How Can You Avoid the Bad, and Especially Ugly Air?
1. Fly early in the morning before the sun has a chance to heat the ground.2. Study the weather and fly later in the morning in stable conditions.
3. Try and fly when the surface conditions are not different from the upper air 3000 feet above you.
Evaluate “Whether to Fly” and pick the good, minimize the bad, and completely avoid the ugly cumulus. Clouds provide for you markers in the sky to tell you what the air is doing, but they need to be approached with caution since they can create their own weather.
Pictures
 |
Early morning when the cumulus clouds are just starting to form. This is on an unstable day with significant moisture in the air. |
|---|---|
 |
Later in the morning as the air is heated and starts to rocket up in areas. Moderate bumps are starting and it is time to seek the ground before it gets worse. |
 |
A good cumulus cloud. A typical cumulus on an average day creating moderate bumps. Wider than it is taller. |
|
A bad cumulus cloud. A healthy cumulus cloud indicating bad air. The cloud is as tall as it is wide. |
 |
An ugly cumulus cloud. |
