Precipitation
7 questions tagged Precipitation — spanning every one of the seven Ws.
What is a freezing drizzle?
Freezing drizzle is very light liquid rain that freezes on contact with cold surfaces, creating a thin, slippery glaze of ice. It can be especially dangerous because it often looks harmless.
Which weather phenomenon is the fastest-moving form of precipitation to hit the ground?
Hailstones are the fastest common form of precipitation in severe storms, because they can fall at very high terminal velocities. Large hail can strike with dangerous impact speed.
How do clouds become heavy enough to rain?
Cloud droplets and ice crystals grow by collision and coalescence until they are large enough to fall. In warm clouds, raindrops usually need to reach about 0.5 mm across before gravity wins over air resistance.
How do hailstones grow inside storm clouds?
Hailstones are built by repeated trips through strong updrafts in thunderstorm clouds, where layers of ice freeze around a small core. They can grow large enough to fall as damaging ice balls.
How do atmospheric rivers deliver huge amounts of rain and snow?
Atmospheric rivers are long, narrow bands of concentrated water vapor in the atmosphere. When they make landfall and rise over mountains, they can produce intense rain and snowfall.
What is graupel?
Graupel is soft, small pellets of snow formed when supercooled water droplets freeze onto snowflakes. It is sometimes called soft hail or snow pellets.
How do atmospheric rivers bring intense rainfall?
Atmospheric rivers are long, narrow corridors of concentrated water vapour that can transport huge amounts of moisture and dump heavy rain when they hit land.