Warm up  Answer these questions in your notebook: 1. What is the difference between humidity and relative humidity? 2. What are clouds made of? 3. List the differences between a cold front and a warm front. Sketch the side profile of each.

QUIZ!

High Pressure Systems  Formed when air moves all the way around a high-pressure center Air sinks down Spreads out toward areas of low pressure

Characteristics  Large and change slowly  Moves slowly clockwise  Clear skies and calm air  This is due to air sinking to a lower altitude, which causes it to warm up a little bit (clouds disappear)

Low Pressure Systems  Surrounds a center of low pressure  Air moves in toward lowest pressure  Moves upward to higher altitude  Upward motion moves air faster

Characteristics  Stormy weather  Form where a warm front meets a cold front  Moves quickly counter-clockwise

Low Pressure System Examples  Tropical Storms  Hurricanes  Winter Storms  Severe Storms

Thunderstorms  Definition: Storm w/ lightning and thunder  Caused by rising moist air  Warm, humid air moves vertically into cooler air above

Thunderstorm Formation: Cumulus Stage 1. Rising humid air (updraft) forms a cumulus cloud.  Energy increases the air motion, forming a cumulonimbus cloud.

Mature Stage 2. Large ice particles form in the low temps near the top of the cloud.  They fall and pull cold air down with them, forming a strong downdraft  Downdraft brings heavy rain or hail  This is the most severe stage of a thunderstorm

Dissipating Stage 3. Downdraft spreads out, which blocks more warm air from moving upward  The blocking of warm air causes the storm to slow down and eventually end

Characteristics  Thunderstorms can form: 1. At a cold front ○ Air can be forced upward quickly 2. Within an air mass ○ Uneven heating produces convection and thunderstorms

Effects of Thunderstorms  Flash Floods  Strong winds  Hail  Lightning  Tornadoes

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