00:00A strong snowstorm breaks out. Then, you start to hear a distinct thunder sound and have sparkles in the sky.
00:08Congratulations, you are one of the few people to have witnessed a snowstorm.
00:13Until recently, scientists were not even sure that it was a real phenomenon.
00:18But now, as more and more videos of this phenomenon appear online, they are trying to understand how these storms are formed and what their real danger is.
00:28One thing is for sure, if you see a lightning during a snowstorm, it is that there is at least 15 cm of snow falling somewhere nearby.
00:36We can even predict strong thunderstorms with snowstorms, but it does not work the other way around.
00:42All the heavy snowfalls do not cause such storms, and scientists are still wondering why.
00:48They think that this beautiful natural event occurs in a similar way to summer storms.
00:54Turbulences in the air raise the hot and humid air near the ground very high in the sky.
00:59As it rises, it cools down and forms clouds filled with tiny crystals of ice, overflowed water and gravel.
01:07When these elements collide inside the cloud, they create an electric charge that causes lightning and thunder.
01:14When it is cold enough for it to snow, the atmosphere does not have as much energy as in summer.
01:19Indeed, the ground does not heat up as much in winter, so there is less heat and humidity in the air.
01:25And there is less water overflowing in the clouds than during a summer storm.
01:31When the right conditions are met, it is usually near large American lakes that this phenomenon occurs.
01:37In these places, the cold air at an altitude mixes with the hot water of the lakes.
01:43This great difference in temperature creates areas where the air rises rapidly.
01:47And these pockets of rising air can cause lightning and thunders during heavy snow storms.
01:53They are also more frequent in the front chain of Colorado and in the high plains.
02:01Another difference between snowstorms and ordinary summer storms is that they are much more difficult to detect.
02:09Snow absorbs sound waves.
02:12So you can only hear the thunder if you are a few kilometers from its source.
02:17It will look more like a deaf rumbling than a powerful and lively blow.
02:22And it is more difficult to see a lightning on a white sky background bursting with flakes.
02:27Thus, snowstorms can take you by surprise and hit you like a regular storm.
02:34However, lightning and thunders that accompany a snowstorm are generally less frequent and less intense than those accompanying summer storms.
02:42Thus, the worst with snowstorms is probably the heavy snowfalls that can cause chaos on the roads and deprive you of electricity for days.
02:52Another rare and impressive winter meteorological phenomenon is the snowball.
02:57Nothing to do with pastry or Asian cuisine. It looks more like a wheel or a snow-covered tire.
03:03You will find these natural formations quite rare in the open prairies of North America or in some remote areas of northern Europe.
03:10For them to form, the conditions must be perfectly united.
03:14First of all, there must be a layer of wet snow on the ground.
03:18The snow must not adhere to the surface, as with ice or very light powder.
03:25Then, a strong but gentle wind where gravity must push the snow just as it should.
03:31As it moves, the snow rolls like a carpet and forms a big bath with a hole in the middle.
03:39Have you ever heard of red lightning, which is also called lightning bolt?
03:43Unlike ordinary lightning that strikes the ground from the clouds, these flash towards the atmosphere, about 80 km above the planet.
03:52They are extremely fast and last only a moment, which makes them very difficult to spot or study.
03:58Flashes are due to an accumulation of electricity in the clouds, just like normal lightning.
04:03They are generally red and can look like jellyfish or carrots and reach up to 48 km wide.
04:12Airplane pilots sometimes see them when they fly at very high altitudes.
04:17Unfortunately, they are not visible from the ground.
04:20Scientists think that flashings occur on all planets that have an atmosphere.
04:26They tested this idea in a laboratory by recreating the atmospheres of these planets and passing electricity through them.
04:33Their hypothesis proved to be accurate.
04:35A cavum is a large circular or oval opening that sometimes appears in certain clouds.
04:40These types of clouds float high in the sky and are often made up of tiny droplets of colder water than the freezing point, but have not yet frozen.
04:49They need ice crystals for this.
04:51When an airplane crosses the cloud, it can bring it these ice crystals.
04:56Once there, the droplets of water freeze quickly, thicken and begin to fall from the cloud.
05:03This creates a hole and, as other droplets freeze nearby, the hole enlarges and its edges extend.
05:11They are called dust whirlwinds, mini-tornadoes, which raise a lot of dust and dirt over time.
05:18They are small whirlwinds filled with tiny debris, and they can occur anywhere in the world.
05:25They are smaller and less powerful than regular tornadoes, but they can still be powerful enough to overturn small objects or lift light objects in the air.
05:36In very hot desert areas, they can be much larger and last longer, sometimes more than an hour.
05:43Dust whirlwinds are formed by sunbeams when the ground becomes very hot.
05:49Once the dust whirlwind has picked up speed, it behaves like a chimney, raising the hot air and lowering the cooler air in the middle.
05:58Dust whirlwinds can be dangerous if they are powerful enough.
06:02It is therefore preferable to stay away.
06:06Have you ever seen a white arch?
06:08They form in the same way as ordinary colored rainbows, but they are much larger.
06:13White arches are formed by tiny droplets in the fog or clouds, instead of big raindrops like in classic sky arches.
06:21But they also appear opposite the sun.
06:24You can therefore observe a white arch in a thin fog when the sun shines.
06:29It is possible to see one when the sun begins to pierce the fog, or if you are near the ocean, where the fog often forms.
06:37As the droplets of water in the fog are tiny, white arches do not have the usual bright colors of the rainbow.
06:44They can even be entirely white and very pale.
06:48Some white arches are difficult to see at first because they melt in the fog.
06:53But once you know how to spot them, they are easy to recognize.
06:58There are atmospheric rivers that flow high in the sky.
07:02They are long and thin streams of air in the atmosphere that carry a lot of water vapor.
07:07Even if you can't see them, they sometimes contain as much water as the Mississippi River carries in a day.
07:14When these celestial rivers reach the earth, the water vapor they contain often turns into rain or snow.
07:22Some are soft and useful, bringing water that dry regions need.
07:27But the biggest and most powerful can cause strong storms of rain or snow.
07:33If they stop moving above certain regions, they can cause floods, landslides and other problems.
07:41One of the most famous atmospheric rivers is called the Pineapple Express.
07:46It takes its name from the hot and humid air it carries from the tropical regions near Hawaii to places like the west coast of the United States.
07:55Mammoths are among the strangest and coolest clouds in the sky.
08:00They look like large pockets or bubbles.
08:04Their shape can vary a lot.
08:06Some look like smooth bubbles, others stretch like long tubes.
08:11Mammoths are generally formed under large thunderstorms.
08:15Inside these thunderstorms, strong winds cause turbulence
08:20which pushes the air and humidity down instead of bringing them up like in ordinary clouds.
08:25This creates these irregular shapes and pocket shapes.
08:29As mammoths are linked to powerful thunderstorms, they are often signs of bad weather, heavy rain, hail or lightning.
08:38In winter, if it's cold enough, they can sometimes bring snow.
08:42Sometimes they appear with other clouds, quieter, but it's quite rare.
08:48The best time to see mammoths is when the sun is low in the sky, for example at dawn or dusk.
08:54The sunlight illuminates the pockets, making them shine and even more impressive.
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