Weather Back to Basics: Clouds

by HPA · August 24, 2017

Weather Back to Basics: Clouds

By Pamelyn Witteman, PhD

We have weather because of the star at the center of our solar system, the SUN. Basically, the uneven heating of the earth surface produces rising thermal columns that cause uplifting of air that brings with it moisture and as it rises to the cooler altitudes, gives off heat, which causes further rising and henceforth, cooling and reaching their dew point then turn into clouds. By now you have flown under enough clouds that when you fly under a cloud, you run into turbulence or otherwise known in pilot jargon, as potholes in the sky. Clouds are beautiful phenomena that can take our breath away as we fly. Clouds tell us how stable the air is at a given altitude. For example, flat clouds can tell us that the air is stable and piled up clouds says that the air is unstable. As pilots, we are able to decide whether it is a good day to fly according to the clouds.

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Cloud Classifications

In 1803, an English scientist by the name of Luke Howard developed the cloud classification we know today. Howard’s purpose was to classify the clouds by their general appearance or shape and height above the ground as the list below describes.

  1. Cirrus clouds are curly and fibrous.
  2. Stratus clouds are layered or stratified.
  3. Cumulus is piled up or lumpy.

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The Cirrus or Cirro clouds are found at higher altitudes, and their bases are commonly located at around 20,000 feet. Alto clouds are found at a mid-level with bases at around 6,000 to 20,000 feet. Clouds lower that 6,000 feet are known as low clouds or state or stratus. Another term that you may be familiar with is “nimbo” or “nimbus,” which means that a cloud is producing precipitation. Furthermore, a cumulonimbus cloud makes thunderstorms due to their shape of being piled or lumpy. However, a Nimbostratus cloud is a low layered cloud that is producing rain. The cumulonimbus clouds are extremely hazardous to pilots and usually avoided.

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When you see the towering cumulonimbus cloud banks ahead of you, perhaps rising to FL400 or above, trouble awaits. Uplifting and downdrafts, hidden by the beautiful opaque clouds are carrying rain, hail, and potentially killer winds. Also, producing more of the same, by sending strong downdrafts or even microburst’s to the ground where they fan out and become uplifted creating another cumulonimbus cloud or clouds. Unless you are equipped with a Forward Looking Infrared (FLIR) Heads up Display (HUD) can lead to you to clouds can grow rocks (i.e. uncontrolled or controlled flight into terrain). Here is where planning, anticipation and responding can save the day if you have not had the training for IFR flight.

In 2012, a demonstration flight with 45 souls on board left Halim Perdanakusuma International Airport in Jakarta, Indonesia. The flight was going well until the pilots heard “TERRAIN AHEAD, PULL UP.” Unfortunately, the pilots did not see any mountains, but only clouds and turned off the terrain and awareness warning system (TAWS) after six blurted out warnings. Minutes later, the aircraft hit the mountains of Mount Salak at 6,000 ft, killing all on board. It was found during the investigation that the pilots did not have the correct aeronautical charts, leading to misjudging the terrain because of the cloud cover. This accident could have been prevented if the pilots had better planning, anticipation, and response to what the aircraft was telling them as well as better understanding of what the clouds were telling them.

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Lenticular Clouds

The aircraft accident leads to discussion about lenticular clouds. Lenticular clouds have been known as a flying saucer or lens shape. They are shaped when air flows along the earth surface and it encounters objects. Lenticular clouds are commonly formed in the mountain terrain, but have been seen on other areas where high objects are found, for example sky scrapers. The wind and water vapor that create lenticular clouds is moving, but the cloud stays in the same location. The reason is due to uplifting and horizontally moving wind that is carried with it moisture that is unseen until it reaches its cooling dew point to form the cloud. The wind and moisture continues on its arch downward where it is transferred back into invisible water vapor, thus leaving the cloud in the same location.

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Wall Clouds

The towering cumulonimbus clouds or thunderheads can also form into what is known as a wall cloud (pictured above) that creates spiraling air up into the bottom of a cumulonimbus cloud. A wall cloud typically produces some of the largest tornadoes due to the spiraling effect. Wall clouds are extremely dangerous to people on the ground and to pilots flying all types of aircraft. In the picture above taken in the Smokey Mountains of North Carolina, you will see that the wall cloud is producing updrafts and downdrafts. An example of updrafts and downdraft air movement would be mammatus or mama clouds. As a pilot, you are probably aware that the best way to see clouds is to take a scenic flight, but be aware of the dangers associated with the beautiful phenomena that we love so much and take care not to stray too close and end up being tossed around like pizza dough. Plan, anticipate, and respond when you are sightseeing. Fly safe and enjoy the view and try not to ingest any mountain goats hiding up in the clouds!

Dr. Pamela Witteman is a freelance academic writer with many years of flying experience.

How it Started

One of my best friends in high school, (Doug Gray) was a private pilot. He offered to take me up for a flight in a 1967 Cessna 150, N6228S. We took off from Calhoun, Georgia, and he took me on a scenic tour of the area, I was hooked. I later found out that my English teacher, (Jan Haluska) was also a flight instructor and the school was offering a ground school course the next year, which he taught, along with flight training with the goal of becoming a private pilot. I managed to talk my dad into funding the training, at the time the total cost was right around $500. Cessna 150 rental rates where $12 an hour, and the 172 we used for cross country was $15 an hour including fuel.

Training Begins

It started August of 1977. The fall semester rolls around, and I am enrolled in ground school, and if memory serves me, we met twice a week. First came the paperwork for my student pilot certificate, which at the time was included with the 3rd class medical. I loved ground school, especially learning navigation, plotting courses on the sectional, again this was before iPads and GPS, so we did a lot of dead reckoning and VOR navigation for cross countries. At the end of the course, I made an 83% on the Private Pilot written exam, remember this was before we had the question-and-answer books that on future test I would consume before taking a written.

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Flying

The fun really began on August 22, 1977, it was my first flight. To my surprise we used the same Cessna 150, N6228S that my friend Doug Gray had taken me for a ride in. The Cessna 150 had a standard VFR instrument panel, with one NAV/COM, and one VOR CDI. No intercom, so no headset, at the time I didn’t know what I was missing. I didn’t get my first headset until I started my instrument training in 2003. I was a big guy, I was 6’ 4” and weighed 245 lbs. but I do not remember being uncomfortable in the 150 even with the instructor in the right seat.

First flight lasted .8 hours, and we accomplished orentation, shallow turns, stability, and effects of flight controls. Over the next few months we added steep 720’s, slow flight, stalls, turns around a point, S-turns, emergencies, landings, (short field, soft field and normal).

Learning

At this point I want to talk about a training experience that still stands out. We were close to solo and were practicing takeoffs and landings. Turning base to final Jan got very upset at the way I was cross controlling the aircraft. Cross control is when you are in, say a left turn, and use opposite rudder to line the nose up with the runway. So, he had me depart the pattern and head east to the practice area, and climbing up to 5500 feet MSL, he had me slow down to just above stalling speed, start a left shallow turn and add right rudder. As the airplane stalled I had the strangest sensation, no roller coaster has ever come close, instead of blue sky in the windscreen I was looking at brown ground, and as far as I could tell we were upside down, through the terror of the moment Jan talked me out of the spin, controls neutral, oposite rudder, pull slowly out of the dive. As we leveled off he asked me what altitude we were at, as I remember it was around 2,800 feet MSL. Then he asked me what would happen if I experenced this on base to final in the traffic pattern. The answer was obvious, I would be a pile of wreckage off the end of the runway with a very short-lived aviation career. Needless to say this cured my cross-control tendencies.

Another training event the sticks out in my mind was the first time we did takeoffs and landings at the High School runway. The runway was 1,500 feet long, not sure of the width, but it seems like we had about 5 feet on each side of the wheels when on the center line of the runway. Landing from the south you also had to go between a cutout in the trees to be able to stop in time on the runway. After getting confortable landing here every runway since seemed huge. I remember landing at Chattanooga (KCHA) on a night cross country and commenting to Jan, that I felt like I could of landed sideways on the runway, it felt that large.

Very soon after this I started wearing old shirts to all my flight lessons, the reason for this occurred on February 8, 1978. The lesson that day was stalls, takeoffs and Landing. As we were taxing back in Jan told me it was time for my first solo. I was very excited, and after some last minute advice from Jan, including watch for floating on landing the plane will be light with him not in the right seat, complete 3 takeoffs and landings to a full stop. It was a blast, and at the end of my shirt was shorter in the back because Jan cut the tail out of it signed and dated my solo [an aviation tradition]. Total flight time accumulated on the day of my solo was 18.1 hours. I was now officially a pilot with solo priveleges.

In my next article I start cross country training, when Jan decided that it would be best accomplished this in the 172. Checking out in N5970R was like moving into a 747, this started a love affair with one of my faviriote planes to date. Since this time I have flown over 900 hours in many different models of the 172 and feel like I am stepping into an old friend every time.

More about Randy here: https://www.flyhpa.com/team/randy-delong/

 

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