Part 4 — Orographic Weather & Winds

What is the difference between stratus and cumulus?

Stratus clouds form layers; cumulus clouds form heaps or piles.

What cloud type is associated with thunderstorms?

Cumulonimbus.

What happens to air on the windward side of a mountain?

It rises, expands, cools, and often produces clouds and precipitation.

What happens on the leeward side of a mountain?

Air descends, compresses, warms, and becomes relatively drier.

What is a rain shadow?

A dry region on the leeward side of a mountain caused by moisture loss on the windward side.

With westerly winds, which mountain slope is usually wetter?

The western, windward slope; moist air rises and cools there.

What are Chinook winds?

Warm, dry downslope winds produced as air descends and compresses on a mountain's leeward side.

Why do descending mountain winds warm?

Increasing pressure compresses the air, causing adiabatic warming.

How does a rain shadow develop?

Windward precipitation removes moisture; descending leeward air warms and dries.

Why do thunderstorms often develop on hot, humid afternoons?

Strong surface heating drives convection; moist rising air cools and condenses.

Why can afternoon heating trigger thunderstorms?

The ground has warmed through the day, increasing instability and upward convection.

What precipitation types are commonly distinguished?

Rain, snow, sleet, hail, and graupel.

How does rain form?

Liquid water droplets grow in clouds and become heavy enough to fall.

How does snow form?

Ice crystals grow in sufficiently cold clouds and reach the surface without melting.

What is sleet?

Ice pellets formed when melted precipitation refreezes before reaching the ground.

What is hail?

Layers of ice built up as strong thunderstorm updrafts circulate particles through supercooled water.

What is graupel?

Soft ice pellets formed when supercooled droplets freeze onto snow crystals.

Name the five forces affecting winds in the review.

Gravity, pressure gradient, Coriolis, centrifugal, and friction.

What is the pressure gradient force (PGF)?

The force caused by pressure differences; it pushes air from high toward low pressure.

Which direction does the pressure gradient force point?

From high pressure toward low pressure, perpendicular to isobars.