Lesson 7 Formation & Dynamics of Severe Weather Sci 20F

S2-4-04 Explain the formation and dynamics of selected severe weather phenomena.Examples: thunderstorms, tornadoes, blizzards, hurricanes, etc.

Read p. 502 – 512 in Science Power 10

Tropical Cyclone, Hurricane, Storm formation video (10 min): https://www.youtube.com/watch?v=W2UDbDXXYGE

Severe Weather Phenomena Research Project

High and Low Pressure Weather Systems

• The force exerted by air particles

• Air moves from an area of high pressure to an area of low pressure.

• The moving air is called wind.

Air Pressure is always changing and depends on factors such as:

• Temperature /Time of day - hotter air has higher pressure

• Altitude – higher up = lower pressure

• Humidity – higher = lower pressure

• Migrating weather systems – Highs and Lows

High and Low Pressure System Explained (3.5 min): https://www.youtube.com/watch?v=aiYyCurh_SU&safe=active

Low Pressure Systems

• Bring: cloudy, rainy or stormy weather .

• Warm air is forced up.

• As it rises, the air spins

• As the air rises, it also cools and water vapor condenses to form clouds.

• Low pressure systems can cause stormy weather and extreme weather events like cyclones, hurricanes and typhoons

• Represented on a weather map by:

• isobars with an “ L ” written in the central most isobar

• arrows traveling clockwise in the Southern Hemisphere or counter-clockwise in the Northern Hemisphere

High Pressure Systems

• Bring: clear blue skies, calm winds, cooler temperatures and lower chance of precipitation.

• Drier air usually results in a greater range of high and low temperatures

• Cold air sinks, as it sinks, the air spins

• As the air falls, it loses humidity and clear skies are the result

• Represented on a weather map by isobars with an “H” in the central most isobar

• Arrows showing which direction the wind is flowing (clockwise in Northern hemisphere, counter-clockwise in the Southern Hemisphere).

Highs and Lows on Weather Maps

Northern vs. Southern Hemisphere

The direction that the air spins is opposite.

Highs vs. Lows

Lows cause cloudy skies Highs cause clear skies

CLOCKWISE = ANTICYCLONE COUNTERCLOCKWISE = CYCLONE

High and Low Pressure System Discussion

1. Why do high pressure systems cause clear skies?

B/c Cool air falls. Cool air does not hold much moisture as warm air, thus preventing the formation of clouds.

2. Why do Low pressure systems cause clouds?B/c Warm air rises and cools, causing water vapor to condense and form clouds

3. Why do high pressure systems cause weather to stay the same for days?

B/c HP systems are large, usually the size of an entire air mass, therefore they take a longer time to move out of an area.

Lesson 7 Formation & Dynamics of Severe Weather Sci 20F

S2-4-04 Explain the formation and dynamics of selected severe weather phenomena.Examples: thunderstorms, tornadoes, blizzards, hurricanes, etc.

Read p. 502 – 512 in Science Power 10

Tropical Cyclone, Hurricane, Storm formation video (10 min): https://www.youtube.com/watch?v=W2UDbDXXYGE

Severe Weather Phenomena Research Project

High and Low Pressure Weather Systems

• The force exerted by_________ particles

• Air moves from an area of _______ pressure to an area of ______ pressure.

• The moving air is called ______________.

Air Pressure is always changing and depends on factors such as:

• ________________ /_______ of day - hotter air has _______________ pressure

• ________________ – higher up = _______________ pressure

• ________________ – higher = _________________ pressure

• _____________________ weather systems – Highs and Lows

High and Low Pressure System Explained (3.5 min): https://www.youtube.com/watch?v=aiYyCurh_SU&safe=active

Low Pressure Systems

• Bring: ______________________________________________

• Warm air is forced ________.

• As it rises, the air ____________

• As the air rises, it also ____________ and water vapor condenses to form ______________.

• Low pressure systems can cause ____________ weather and _____________ weather events like ___________, ___________ and ________________

• Represented on a weather map by:

• ______________ with an “ ___ ” written in the central most isobar

• arrows traveling clockwise in the __________________ Hemisphere or counter-clockwise in the ________________ Hemisphere

High Pressure Systems

• Bring: _______________________________________________________

• _____________ air usually results in a greater range of high and low temperatures

• Cold air _________, as it sinks, the air _____________

• As the air falls, it loses _____________ and __________ skies are the result

• Represented on a weather map by _______________ with an “___” in the central most isobar

• Arrows showing which direction the wind is flowing (clockwise in __________________ hemisphere, counter-clockwise in the __________________ Hemisphere).

Highs and Lows on Weather Maps

Northern vs. Southern Hemisphere

The direction that the air spins is __________________.

Highs vs. Lows

Lows cause ____________ skies Highs cause ___________ skies

CLOCKWISE = ________________ COUNTERCLOCKWISE = _____________

High and Low Pressure System Discussion

1. Why do high pressure systems cause clear skies?

2. Why do low pressure systems cause clouds?

3. Why do high pressure systems cause weather to stay the same for days?