Thirteen of the coolest cloud formations.

Current Sun Image

1. Kelvin–Helmholtz instability waves or KHI From U of I

KHI

If you ever see these you should watch them for a little while, because they will act like ocean waves and break, then crash, and they will be gone within minutes. It was first written about by Kelvin (the same guy that came up with the Kelvin temperature scale) and Helmholtz.

It is really a neat process that makes these clouds. You need a strong density difference, and some kind of wind shear along this difference. Almost like the difference at the surface of the ocean, where the water is much more dense than the air, and the air has a stronger wind speed.

2. This falls into a few different categories From link NASA

cirrus

In this picture there are sun dogs, sun pillars, iridescent clouds, and a halo. Check out this awesome description of halos.

3. Iridescent cloud From EvanFromHeaven on Picasa

cirrus

These beautiful and rare clouds are formed when ice crystals are fairly uniform in size and shape. You would not expect this uniformity to ever happen but, in really high (>25,00 foot) or really cold (<-35C) clouds, it happens quite often. The ice crystals act as prisms and separate the light into different spectrum's. The sun is hitting each part of the cloud at a different angle. These clouds would not usually be so rare, but the actual sun has to be covered up by something (a thicker cloud here)

4. Supercell

fake isabel

This picture is not the best picture of a supercell but I use it because it is funny. This picture was a viral e-mail in 2003. It was labeled as hurricane Isabel, which it is not. It is a supercell thunderstorm that was on the decaying side of Tropical Cyclone Graham

A supercell, is just a rotating thunderstorm. This is better defined by Jeff Haby. Once this rotation is seen on doppler radar a tornado watch will be issued, once someone sees a funnel cloud, or a hook echo is seen on doppler radar, a tornado warning will be issued.

5. Pyrocumulus

These clouds happen over forest fires. All of my two regular readers, will know that I fought forest fires for six years and have seen my share of these. They happen because of the ash put into the atmosphere by the fires. Water can cling to this ash, and make water droplets, better than it can most other stuff in the atmosphere. It is called Cloud Condensation Nuclei (CCN) by meteorologists. This introduction of CCN can cause storms and is an area of interest to companies that do cloud seeding.

6. Pileus From U of I

pileus

Pileus clouds form when air flowing through an area is blocked by a thunderstorm or mountain, and has to go over or around the obstacle. In the case of the picture above the air was forced over a thunderstorm. When air goes upward it cools and condenses. If it ends up reaching it's dew point then it will form a cloud. These clouds are usually so high in the atmosphere that they will be made entirely of ice, and therefore have that fuzzy look.

7. Lenticular From SquarelyInWellington

Lenticular clouds are formed downstream of mountain ranges. The air is pushed up over the mountain and when it comes back down it will go too far down. This causes the air to be negatively buoyant, which makes it go back up. The air will continue this cycle until it reaches an equilibrium. Sometimes you can see this happening because the air will reach its dew point at the top of each cycle.

8. Crepuscular Rays From Ian Loxley

I guess this is not really a cloud per se, but it is still cool. I get asked what this is called a lot. It is just where you can see individual sun rays from gaps in the clouds. Wikipedia has a great explanation of these.

9. Noctilucent From polarimage

These are some of the rarest clouds on earth and I would say that most of the pictures claiming to be them are not. These clouds live almost 50 miles above the Earth in the Mesosphere. The only way to see them is at high latitudes at night. They reside so high that they are rarely seen. Most water vapor in the atmosphere is in the Troposphere. I suggest reading about them at the polar image link above or at Wikipedia

10. Virga From NOAA

virga

Virga is when a precipitation is evaporated before it hits the ground. This can cause down bursts because it cools the air around it very quickly, and the cooled air sinks.

11. Arcus From UCAR

Arcus clouds are rad. Sometimes you will see a huge circle of cloud in the sky, which is an arcus cloud. These are formed from outflows from thunderstorms. This outflow acts as a mini cold front and makes a cloud that can go all the way around where the original thunderstorm was.

12. Cirrus From NOAA Photo Library

cirrus

Cirrus are not rare, but they are one of the most beautiful clouds. In Latin it means "lock or tuft of hair". These are really high clouds composed entirely of ice. In the mid-latitudes you can assume they are 25,000-30,000 feet high.

13. Waterspout From NOAA Photo Library

Waterspout is just a tornado over water. I wonder what a tornado over a cornfield would be? An cornado? Dr. Chuck Doswell has an explanation and of funnier names.

UPPERWEATHER.COM -Meteorological Musings

Thirteen of the coolest cloud formations.

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