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Questions and Answers
What characterizes a warm front?
Which front is associated with more violent weather conditions?
What best describes the characteristics of a stationary front?
What primary conditions are required for thunderstorms to develop?
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What happens during the active stage of a thunderstorm?
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How does a cold front affect weather conditions after its passage?
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What is a defining feature of an occluded front?
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Which statement is true regarding thunderstorm occurrence in the United States?
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What defines a tropical storm according to the wind speed criteria?
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Which part of a hurricane experiences the greatest wind speeds?
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Which factor is considered the most important in determining hurricane damage?
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What happens to a hurricane when it moves over cooler ocean water?
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What are hurricanes called in the western Pacific region?
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During which part of the year do hurricanes typically develop most often?
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What is the diameter of the eye of a hurricane approximately?
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What effect does the shape of the ocean bottom have on hurricane damage?
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What is the main characteristic of a continental polar (cP) air mass?
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Which air mass is primarily responsible for bringing lake-effect snow in North America?
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Where do maritime tropical (mT) air masses primarily originate?
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What type of air mass is formed over land and is likely to be dry?
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Which type of air mass would most likely bring precipitation to the western mountains of North America?
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What defines the source region of an air mass?
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During which season does the continental polar (cP) air mass typically bring cool relief?
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What is the primary influence of the continental tropical (cT) air mass outside its source region?
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Study Notes
Air Masses
- Large bodies of air that can be 1600 kilometers (1000 miles) or more across
- Air masses acquire properties from their source region
- Air masses are classified by their source region and the characteristics of the surface in the source region
- Polar (P) air masses form in high latitudes and are cold
- Tropical (T) air masses form in low latitudes and are warm
- Continental (c) air masses form over land and are likely to be dry
- Maritime (m) air masses form over water and are humid
- The four basic types of air masses are Continental Polar (cP), Continental Tropical (cT), Maritime Polar (mP), and Maritime Tropical (mT)
- In North America, cP and mT air masses have a particularly important influence east of the Rocky Mountains
Air Masses and Weather in North America
- Continental Polar (cP) air masses are responsible for lake-effect snows
- cP air mass crosses the Great Lakes picking up moisture from the lakes
- Snow occurs on the leeward shores of the Great Lakes
- Continental Polar air masses from Northern Canada and interior of Alaska can bring cold, dry air in the winter and cool relief in the summer
- Maritime Tropical (mT) air masses from the Gulf of Mexico and the Atlantic Ocean bring warm, moist, unstable air, which leads to precipitation in the eastern United States
- Continental Tropical (cT) air masses form over the Southwest and Mexico and are hot and dry
- Maritime Polar (mP) air masses bring precipitation to the western mountains and can influence the northeastern United States, causing "Nor'easters" in New England with cold temperatures and snow
Fronts
- Boundaries that separate air masses of different densities
- Fronts force warmer, less dense air aloft and form a wedge of cooler, denser air
- Warm fronts are shown on maps with a red line with semicircles and are characterized by a gradual slope, lower clouds as the front nears, a slow rate of advance, and light-to-moderate precipitation
- Cold fronts are shown on maps with a line with triangles and are characterized by a steep slope, faster advance than warm fronts, and more violent weather than warm fronts
- Stationary fronts have nearly parallel airflow on both sides of the front and remain relatively stationary
- Occluded fronts occur when an active cold front overtakes a warm front, forcing the warm air upward and creating complex weather conditions with precipitation
Thunderstorms
- Occur when cumulonimbus clouds produce heavy rainfall, lightning, and sometimes hail
- Approximately 2000 thunderstorms are in progress at any one time, and 100,000 occur annually in the United States
- Occur frequently in Florida and the eastern Gulf Coast region
- Thunderstorms require warm, moist, and unstable air (lifting)
- High surface temperatures are common in the afternoon and early evening
- Thunderstorms require a continuous supply of warm air and moisture, which leads to updraft and downdraft formation
- Heavy precipitation indicates the most active stage of the storm
- The cooling effect of precipitation marks the end of thunderstorm activity
Hurricanes
- Winds exceeding 119 kilometers (74 miles) per hour with rotary cyclonic circulation
- Form between 5 degrees and 20 degrees latitude
- Are also known as typhoons (western Pacific) and cyclones (Indian Ocean).
- The North Pacific has the highest number of hurricanes per year
- The hurricane's eye wall is characterized by rising air, intense convective activity, a wall of cumulonimbus clouds, highest wind speeds, and heaviest rainfall.
- The eye of a hurricane is the calm center with a diameter of about 20 kilometers (12.5 miles)
- Hurricanes can have winds reaching 300 km/hr and generate 50 foot waves at sea
Hurricane Formation and Decay
- Hurricanes can form in all tropical waters except the South Atlantic and Eastern South Pacific
- Hurricanes obtain energy from condensing water vapor
- Develop most frequently in late summer when warm water temperatures provide energy and moisture
- The initial stage isn't well understood
- Tropical depressions have wind speeds under 61 kilometers (38 miles) per hour
- Tropical storms have wind speeds between 61 and 119 kilometers (38 and 74 miles) per hour, at which point they are given names
- Hurricanes diminish in intensity when they move over cooler ocean water, move onto land, or when the large-scale flow aloft is unfavorable
Hurricane Damage
- Factors that influence hurricane damage include:
- Hurricane strength (most important factor)
- Size and population density of the affected area
- Shape of the ocean bottom near the shore
- The Saffir-Simpson scale ranks the relative intensities of hurricanes
- Hurricane damage includes:
- Storm surge: a large dome of water that sweeps across the coast where the eye makes landfall, spanning 65 to 80 kilometers (40 to 50 miles) wide
- High winds, heavy rain, and flooding
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Description
Explore the characteristics and classifications of air masses, including Polar and Tropical types. Learn how these air masses affect weather patterns, specifically in North America, such as lake-effect snow. This quiz covers essential concepts related to meteorology and climate.
