Chapter 20 Reading Guide

Weather

20.1 Air Masses and Weather

What is an air mass and how does it typically gain its specific characteristics?

An air mass is a large body of air with similar characteristics throughout. It gains these characteristics from the air temperature and humidity in its place of origin. As it moves, it takes these characteristics with it, but may also change in response to new surroundings.

Record the characteristics of the five main types of air masses.

Place of Origin / Direction of Movement / Weather Impact
Continental Arctic (cA) / Artic, Polar Regions / Southerly / Extreme cold, little precipitation
Maritime Polar (mP) / High latitude oceans / Southerly and toward the U.S. center / Fog, clouds, precipitation
Continental Polar (cP) / Inland Alaska and Canada / Southeasterly / Cold, little precipitation except Lake Effect snow
Continental Tropical (cT) / Southern deserts / Northerly / Heat waves, drought
Maritime Tropical (mT) / Warm tropical oceans / Northerly and toward the U.S. center / Heat, humidity, thunderstorms

20.2 Fronts and Lows

1. Define and explain the stage at which a low-pressure system produces the most intense storm.

A low-pressure system creates the most intense storm after about 12-24 hours, when its warm front becomes occluded between cool air pushing northward in front of it and cold air pushing southward behind it.

Complete the organizer with information describing different fronts and the weather they bring.

1. Warm Front
Forms when warm air advances on cooler air; gradual slope as warm air rises slowly moves slowly; large areas of precipitation, lasting several days. / 2. Cold Front
Forms when cold air advances on warmer air; steep slope as cold air sinks quickly moves quickly, any precipitation is brief; brings thunderstorms or cool breezes, depending on humidity in displaced warm air.
3. Occluded Front
Front forms when warm front is trapped between two cold fronts often causes cloudiness, precipitation. / 4. Stationary Front
Forms when front doesn’t move; warmer air rises within the front, causing precipitation; heavy storms due to stationary precipitation.

20.3: Thunderstorms and Tornadoes

Complete the organizer by listing the conditions and locations where thunderstorms most often develop, then listing and defining their possible effects.

THUNDERSTORMS DEVELOP

  1. a.) in moist stable air
b.) in warming temps of
afternoon
c.) at frontal boundaries or
when warm air hits other
obstacles

and can cause

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2. Lightning / 4. Tornadoes

 

which is which are



3. an electrical discharge when positive and negative charges in a thundercloud collide and form a spark / 5. Violently rotating columns of air that touch the ground.

List and describe some ways that meteorologists predict tornadoes and warn people of the related danger.

Meteorologists use conventional radar to map precipitation in an area and Doppler radar to identify the wind directions within a storm. Doppler radar can identify the mesocyclone wind movements often associated with tornadoes. Tornado watches and warnings advise people of the possible tornado danger at any given time.

20.4: Hurricanes and Winter Storms

Complete the organizer to help you track the steps in the formation, development, impact, and weakening of a hurricane.

1. Mild atmospheric disturbance over tropical
ocean

2. Humid Air Rises
8. storm weakens over cooler land or water

7. Storm nears land causing:
a.)storm surge
b.)damaging winds
c.)heavy rain
d.)inland flooding
e.)heavy surf
3.Air cools and condenses releasing heat

4. Cycle of air movement continues

6. Storm moves according to global wind patterns

\ 

5. Coriolis effect rotates air in the storm.

List and describe the characteristics of a blizzard: A blizzard is a special kind of mid-latitude low-pressure system. It has winds over 56 km/hour, temperatures below -7C, and falling or blowing snow that reduces visibility.

20.5: Forecasting Weather

In the organizer below, record important elements of the forecasting process.

3.surface observations measure temperatures,dew point, barometric pressure, wind speed and direction
1. Satellites take visible and infrared pictures
2. Radiosondes measure temperature, humidity, pressure

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/

4. Station models

+ =

5. surface weather map
6. knowledge of local weather patterns
7. forecasts

Explain why it is important that weather station models and surface maps be readable to meteorologists in any country:

In this way, meteorologists around the world can share data, and forecast farther ahead and provide necessary warnings of bad weather.