simplified meterology

Rain

From Climate Change Matters (link ):

“Raindrops are formed from water condensing out of moist air that cools. This can occur in three main ways:

  • over mountain ranges as moist air is forced to rise into cooler altitudes,
  • as warm moist air meets colder air at a “cold front” or
  • in storm clouds when hot moist air rises into cooler altitudes as the ground is heated during summer days.

For rain to form, small dust particles or ice particles must be present in the air. Such particles attract the water as it condenses from the cooling air forming larger and larger raindrops. When the raindrops become too large to be supported by the upward wind within the cloud, they begin to fall. Large drops are formed when strong updraughts hold the drops in the clouds allowing more water to accumulate in each drop.”

From Weather Whiz Kids (link):

“Water droplets form from warm air. As the warm air rises in the sky it cools. Water vapor (invisible water in the air) always exists in our air. Warm air holds quite a bit of water. For example, in the summer it is usually very humid. When enough of these droplets collect together, we see them as clouds. If the clouds are big enough and have enough water droplets, the droplets bang together and form even bigger drops. When the drops get heavy, they fall because of gravity, and you see and feel rain.

What causes rain:When clouds develop or rain occurs, something is making the air rise. Several things can make this happen. Mountains, low-pressure areas, cold fronts, and even the jet stream.”

 

Snow

A simple video on youtube: link

From Climate Change Matters (link ):

“Snow is created when very cold conditions freeze the water as it condenses in the clouds. The crystals of snow form like rain around dust, but form light transparent ice crystals we know as snow, instead of raindrops. For snow to land, the temperature must be below 0°C, the freezing point of water.

Sleet is snow that has semi-melted while falling, having none of the beauty of snow, lacking the intricate hexagonal symatry of snow flakes and all the charisma of very cold rain!”

Thunderstorms

From Weather Whiz Kids (link):

“The basic ingredients used to make a thunderstorm are moisture, unstable air and lift. You need moisture to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. Finally, you need lift. This can form from fronts, sea breezes or mountains.”

Hail

From Climate Change Matters (link ):

“Intense updraughts created in a severe storm can suspend very large drops of water and even blow drops back up high into the tops of the storm clouds. If the rising droplets reach a high enough altitude the water freezes, forming hail. If the process of falling and being blown back high into the storm cloud continues, larger and larger hailstones are formed. Ultimately the hailstones gain enough mass to fall to Earth.

Hail is usually associated with tropical or summer thunderstorms. Stones as large as cricket balls are not uncommon in Australian storms.”

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