Air Masses Large bodies of air formed when a body of air hangs over a region and takes the temperature and humidity from that region.

Air MassesLarge bodies of air

formed when a body of air hangs over a region and takes the temperature and humidity from that region

4 types

1. Continental polar

•cold and dry

•effects Michigan the most

• 2. Maritime polar

• cold and moist

• 3. Continental Tropic

• warm and dry

• 4. Maritime Tropic

• warm and moist

• effects Florida

FRONTSFRONTS

Boundary between two air masses

4 types:

1. cold

2. warm

3. stationary

4. occluded

COLD FRONT

• Cold air mass pushes a warm air mass

• steep slope

• brings thunderstorms or severe weather

Cumulonimbus clouds

WARM FRONT

• Warm air mass pushes a weaker cold air mass

• little temperature change

• brings steady rain

stratus clouds

STATIONARY FRONT• When two air

masses meet but cannot push each other

• steady rain for days

OCCLUDED FRONT• A cold front overtakes a warm

front

• warm air forced up rapidly

• LOW pressure

• and storms L

Causes of wind• 1. Uneven heating of the Earth

creates:2. Differences in air pressure

creates: High pressure area and low pressure

areaAll winds blow from a High pressure

to a Low pressure

Works with other things too!!

Clicker

• What caused the can to crush?

a) Increased external air pressure

b) Decreased external air pressure

c) Water vapor condensing

d) Liquid water evaporating SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

3. CONVECTION CELLS

• Warm air rises; cool air sinks

4. CORIOLIS EFFECT• Caused by the rotation of the earth• Earth rotates on the average 750mph

– faster at the equator– Causes winds to be deflected tothe right in the – Northern Hemisphere

Coriolis Forceclockwise rotation, the deflection is to the left of

the motion of the object; in one with counter-clockwise rotation, the deflection is to the right.

WESTERLIESBlows from the west to the east

Effects the weather the most in the US

TRADE WINDS OR EASTERLIESBlow from the east toward the equator

Clicker

• Which way do winds blow?a) From high pressure to low pressure

b) East to north

c) Low pressure to high pressure

d) South to EastSMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

Isobars- line that connect areas of equal air pressure

Instruments

1. Anemometer- measures wind speed

2. Wind Vane- measures wind direction

Isobars and relative wind speed• Close isobars=high wind

speed• Low Pressure System:

Increased cloudiness, winds, temperatures, and chance of precipitation.

• High Pressure System: Indicates clear, calm conditions with reduced chance of precipitation.

Cumulonimbus clouds-Contain heavy rain, lightning, hail and wind

-Possible tornadoes-Associated with a cold front

Two of the most important ingredients for thunderstorm formation are instability (unstable air) and moisture.

During a thunderstorm, the Earth's surface has a positive charge. Because opposites attract, the negative charge at the bottom of the thunder cloud wants to link up with the positive charge of the Earth's surface.

1. The electricity passes through the air and starts it vibrating. The vibrations cause sound.

2. The lightning is also very hot and heats up the air around it. Hot air expands and the air gets bigger very quickly, and pushes apart the air particles.

These vibrations are what you hear and call thunder

THUNDERSTORM DOWNBURST

Form at the base of a cumulonimbus cloud The formation of tornadoes is the result of

warm, moist air meeting cooler, dry air, and creating instability in the atmosphere.

Season: spring to mid-summer

Strongest wind speeds

Ranked on the (Enhanced) Fujita Scale

FUJITA SCALE

EF-0

EF-1

EF-2

65-85 mph

86-110 mph

111-135 mph

EF-3

EF-4

136-165 mph

166-200 mph

EF-5 Over 200 mph

Cyclone over warm water Pre-existing storm Has an eye – low pressure in the center

Has a storm surge- Most dangerous part of a hurricane Wall of water near the eye Causes most destruction and loss of life

ANDREW-1992

Hurricane season June 1- Nov.30 Tropical Depression Wind speeds

between 20 and 34 knots (23-39 mi/hr)

Tropical Storm Wind speeds between 35 and 64 knots (40-73 mi/hr)

Hurricane Wind speed greater than 64 knots (74 mi/hr)

Rotation : Clockwise or Counter clockwise ?

Counter clockwise

The eye is the center of the storm. The eye wall surrounds the eye. The

strongest winds and heaviest rains are found in the eye wall.

Rain bands are long, arching bands of clouds and thunderstorms that spiral out from the eye wall.

Hurricane season June 1- Nov.30

if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength.

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