Lenticular Clouds
We think these clouds look like delicious wisps of marshmallow! But did you know that this type of cloud is also often mistaken as a UFO? Due to their often saucer-like shape, some people tend to jump to the wrong conclusion!
So how are Lenticular clouds formed? They are formed when a current of moist air is forced upwards as it travels over a mountain, causing the moisture to condense and form a cloud. Lenticular clouds also tend to hang around in the same stationary position for days. This is because the flow of moist air continually resupplies the cloud with the moisture it needs to retain its position and shape.
It is also interesting that this lenticular cloud is hovering over these large fans. It is these large fans that are able to supply a constant flow of air to the cloud.
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Anvil Clouds
You’d be forgiven for looking at this photograph and thinking it had captured an explosion going off. This photograph actually shows an anvil cloud, and they are often associated with the loud explosion-like noise of thunder because the cloud forms in the upper part of a thunderstorm.
Even if a thunderstorm is miles away, lightning can still strike from these gloomy looking anvil clouds. The National Weather Service state that anvil clouds can spread up to “hundreds of miles downwind from the thunderstorm itself”.
So how do anvil clouds form such an unusual shape, you ask? Rising air in a thunderstorm spreads out and expands as it clashes against the bottom of the stratosphere. Because anvil clouds mostly contain ice particles, the air in the stratosphere is warmer than that contained in the cloud. As a result, the anvil cloud is prevented from spreading into the stratosphere and it maintains a flat-looking top.
The white streaks falling out of the edges of the anvil cloud is actually snow, however by the time this snow reaches the earth’s surface, it has been transformed into rain.
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Cirrus Kelvin-Helmholtz Clouds
Notice how these clouds look like a giant wave in the sky? These clouds are called Cirrus Kelvin-Helmholtz clouds, and they are one of the most distinctive cloud formations. These clouds often sit at heights above 16,500 feet – Yikes! If you see one of these clouds, it’s best to pause for a moment and admire it, because only within a minute or two of forming, this type of cloud often disperses again.
How does this cloud get its unique wavy shape? The answer is quite simple actually. When one layer of air slides across another layer moving at a different speed or in a different direction then the cloud forms the wavy shapes as pictured below. These types of clouds are not associated with any specific weather conditions, and therefore can form on even the most sunniest of days.
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Fallstreak Hole
We find this photograph of a Fallstreak Hole cloud fascinating! It almost looks as though the sky is beginning to cave in. Fallstreak Holes, also known as ‘hole-punch clouds’, occur when part of a cloud of water droplets freezes into ice crystals. Sometimes the ice crystals grow large enough to fall below the clouds, and this results in a Fallstreak Hole type cloud as pictured.
Another amazing fact about this type of cloud is that the hole grows in size, sometimes reaching 50km across merely an hour after the hole began! For the hole to form, the droplets in the cloud layer need to be below 0˚ Celsius, but not necessarily frozen.
The tiny water droplets need temperatures as low as –40˚ Celsius in order to freeze into solid ice crystals. We will definitely be looking out for this unique type of cloud from now on!
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Mammatus Clouds
Look at these fascinating, circular clouds poking through the sky’s surface! This type of cloud is called a Mammatus cloud. They are a rare sight to see, and are an example of clouds in sinking air.
There is a common misconception that Mammatus clouds are a sign that a tornado is about to form, however this has been proven incorrect. Instead, Mammatus clouds signal that the worst part of a thunderstorm has actually passed. These clouds are linked to the anvil cloud, as Mammatus typically develop on the underside of a thunderstorm's anvil.
When sunlight reflects off the underside of the Mammatus cloud, as pictured, it is a beautiful sight. Mammatus clouds can occur for a long period of time if the sinking air contains large drops and snow crystals, as these take longer to dissolve and evaporate.
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Polar Stratospheric Cloud
We find the neon ring around these clouds fascinating! Just look at those bright and beautiful colors. Polar stratospheric clouds are also known as nacreous clouds, and this is named after nacre, meaning ‘mother of pearl’. The cloud is known as ‘mother of pearl’ due to its iridescent nature.
Polar stratospheric clouds occur in the polar stratospheres at altitudes ranging from 15,000–25,000 meters. Although the stratosphere has very dry conditions, in extremely cold polar winters, stratospheric clouds such as the polar stratospheric cloud is able to form due to the colder, and therefore more moist conditions during this time. Did you know that this is also another type of cloud often mistaken for a UFO? This is mainly due to their shiny nature and their often flat shape.
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Roll Clouds
How wonderful are these tubes of cloud in the sky? Appropriately named a roll cloud, these types of clouds are extremely rare. A roll cloud is a low, horizontal, tube-shaped cloud. Do not fear however, because contrary to popular belief, these types of clouds do not have anything to do with tornadoes!
Roll clouds appear as though they are rolling in the sky, however they are a solitary cloud known as a soliton. A soliton is simply a wave that has a single crest and moves without changing speed or shape.
If you travel to Queensland, Australia, you have a very good chance of seeing an example of a roll cloud. Famously known as the Morning Glory cloud, this popular occurrence is due to the sea breezes that develop over the Cape York Peninsula and the Gulf of Carpentaria.
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Undulatus Asperatus
Just look at those lovely, bright sunset colors! The Undulatus asperatus cloud is a newly recognised and rare cloud formation that was discovered and named as recently as 2009. This was a pretty big deal for weather experts and scientists, as a new cloud formation had not been discovered since 1951!
Undulatus asperatus simply means agitated waves. These types of clouds may look stormy and dark, however they can sometimes appear and disappear without a storm occurring. These clouds have become common occurrences in the Plains states of the United States during the earlier hours of the day. Due to the recent discovery of these clouds, scientists are still trying to discover more information about these clouds.
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Cirrus Kelvin-Helmholtz Clouds
Here is a photograph of another Cirrus Kelvin-Helmholtz cloud, however you may notice that this wave starts off small and gradually becomes larger and less defined.
As mentioned earlier, this is because layers of air form these clouds, however they just as easily destroy them too. But how did this strange cloud formation get its name? This type of cloud was first described in the late nineteenth century by Scottish physicist Baron Kelvin (1824-1907 and German physicist Hermann von Helmholtz (1821-94). The title of the cloud combines both men’s last names, linking back to the cloud’s origins.
Many of us have most likely never seen this type of cloud before, but there is an understandable explanation for this. Weather experts claim that there is usually “insufficient moisture present to generate cloud and render the pattern visible”. These clouds do occur commonly in the upper troposphere, however these often remain invisible to the human eye.
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Fallstreak Hole
Here is another type of fallstreak hole, however you will notice it is quite different to the previous one. This photograph of a fallstreak hole has been taken from a position almost directly underneath the cloud.
On the other hand, the first fallstreak hole photograph was taken from more of a side-on position much further away in the distance. Did you know that scientists believe that aircraft can also cause this type of cloud to form? They believe that when the aircraft is flying through the clouds, the expansion of the air as it passes over the aircraft wings could sometimes be cool enough to set off the freezing process of the tiny droplets of water.
It is once these droplets of water freeze that they begin to drop through the surface of the cloud and create this fallstreak hole effect. Who ever knew clouds could be so fascinating? Now you know next time you see this ominous-looking cloud that the sky isn’t really falling in.
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Lenticular Clouds
How amazing is this photograph? We have never seen such a fascinating sight in our lives! This cloud is another example of a lenticular cloud.
As you can see, they often occur around mountains or hills. Due to their often rare locations, lenticular clouds are rare to see. Photographers especially look out for this type of cloud during sunset, as a brilliant array of colors fill the cloud and create a beautiful display.
The shape of this type of cloud often depends on the wind speed and the shape of the mountains. Lenticular clouds can remain in their position for hours, or even days. So although they are a rare sight, if you do see one then you can be assured that it will remain there for quite some time.
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Mammatus Clouds
This photograph is a great example of mammatus clouds occurring after a thunderstorm over a cityscape. This is a rare and wonderful sight, and you can also see an example of the sun reflecting off the clouds.
But how do mammatus clouds form this unusual shape? Because of the cloud’s high concentration of ice crystals and water droplets, the saturated air is heavier than the surrounding air and it therefore sinks back towards the earth. The sinking air will be cooler than its surroundings and continues to sink downward, creating the rounded formations of cloud as shown in the below photograph.
Although mammatus clouds can last for long periods of time, over time, the cloud droplets do eventually evaporate and the cloud formation will disappear.
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Polar Stratospheric Cloud
Here is another beautiful example of a Polar Stratospheric Cloud, but when is the best time to spot one of these amazing cloud formations? These clouds are best observed when during twilight when the sun is between 1 and 6 degrees below the horizon.
Although they might be quite specific measurements, it’s best to always keep an eye out for unusual and colourful cloud formations because you never know what rare type of cloud you’ll discover!
Did you know that Polar Stratospheric Clouds are often linked to holes in the ozone layer? Scientists exclaim that this is because the clouds “support chemical reactions that produce active chlorine which catalyzes ozone destruction, and also because they remove gaseous nitric acid, perturbing nitrogen and chlorine cycles in a way which increases ozone destruction”.
Because these clouds sit at higher altitudes and because of the natural curve of the Earth’s surface, these clouds receive sunlight from below the horizon. This creates the amazing glow as seen as in this photograph.
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Roll Clouds
Here is another awesome example of a roll wave, and this one looks like a giant tunnel in the sky! So exactly how are these incredible cloud formations developed? Scientists explain that roll clouds are usually formed by outflows of cold air from sea breezes or cold fronts in the absence of thunderstorms.
Roll clouds are sometimes likened to a similar type of cloud known as the shelf cloud. However, unlike shelf clouds, roll clouds are completely detached from other cloud features. You can see in this photograph how the roll cloud is a formation all on its own, and it does not contain other cloud formations attached to it. This makes the roll cloud a spectacular sight in the sky, and they often look like a very smooth cylinder.
This type of cloud is often located along the gust front, and this is another reason why it has such a tubular shape.
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Undulatus Asperatus
Here is another example of a fascinating Undulatus Asperatus cloud. You’ll notice its almost ominous appearance, and this is because some Undulatus Asperatus clouds can also appear in the hours following thunderstorm activity. The cause of these types of clouds is presently unknown, and scientists believe that they are quite unusual atmospheric structures.
Although most low cloud decks are have a flat bottom, Asperatus clouds appear to have large vertical structure underneath. Undulatus Asperatus clouds have been linked to both lenticular clouds and Mammatus clouds.
Scientists believe the cloud formation has similarities with lenticular clouds because of their ability to form around mountains, and Mammatus clouds because of their link to thunderstorms. They have even been associated at time with a type of dry downward wind that flows off mountains!
