Earth & Space Science Chapter 14: Air Masses
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Questions and Answers

What is a common factor in the formation of all thunderstorms?

  • Cold, dry air
  • Low atmospheric pressure
  • Unequal heating of the Earth's surface
  • Warm, moist air (correct)

    • What is the main reason why thunderstorms are common in the afternoon and early evening?

  • Buoyancy and instability are enhanced by high surface temperatures (correct)
  • Downdrafts are more prevalent during this time
  • There is a continual supply of warm, moist air available
  • Surface heating is sufficient to grow a towering cumulonimbus cloud

    • What is the typical lifespan of a single cumulonimbus cloud within a thunderstorm complex?

  • Days
  • 1 hour (correct)
  • 10-15 minutes
  • Several hours

    • What is the name given to thunderstorms that produce high winds, damaging hail, flash floods, and tornadoes?

    <p>Severe thunderstorms</p> Signup and view all the answers

    What is the estimated number of thunderstorms that occur on Earth at any given time?

    <p>2,000</p> Signup and view all the answers

    What is the typical diameter of suction vortices within a strong tornado?

    <p>30 feet</p> Signup and view all the answers

    What is the typical speed of updrafts in thunderstorms?

    <p>40-60 mph</p> Signup and view all the answers

    What percentage of thunderstorms produce tornadoes?

    <p>1%</p> Signup and view all the answers

    What is the main factor that contributes to the development of downdrafts in thunderstorms?

    <p>Cooling effect of falling precipitation</p> Signup and view all the answers

    What is the estimated number of thunderstorms that occur in the US each year?

    <p>100,000</p> Signup and view all the answers

    What is the typical size of a mesocyclone?

    <p>2-6 miles across</p> Signup and view all the answers

    Where are tornadoes most likely to occur in the United States?

    <p>Central US</p> Signup and view all the answers

    What is the term used to describe the rotating column of air in a tornado?

    <p>Vortex</p> Signup and view all the answers

    What is the average speed of a tornado?

    <p>30 mph</p> Signup and view all the answers

    What is the estimated maximum wind speed in a tornado?

    <p>300 mph</p> Signup and view all the answers

    What is the direction that most tornadoes travel?

    <p>Northeast</p> Signup and view all the answers

    What is the average width of a tornado?

    <p>330 feet</p> Signup and view all the answers

    What is the typical wind speed of a weak tornado?

    <p>90 mph</p> Signup and view all the answers

    What is the maximum wind speed of an extremely violent tornado?

    <p>310 mph</p> Signup and view all the answers

    In which months are tornadoes most frequent?

    <p>April, May, June</p> Signup and view all the answers

    What is a major factor in the destruction caused by a tornado?

    <p>The wind speed</p> Signup and view all the answers

    What percentage of tornadoes are classified as EF-4 and EF-5?

    <p>2%</p> Signup and view all the answers

    What is the primary purpose of the Storm Prediction Center (SPC)?

    <p>To provide accurate and timely forecasts for severe thunderstorms and tornadoes</p> Signup and view all the answers

    What is the typical time interval for a tornado watch?

    <p>4 to 6 hours</p> Signup and view all the answers

    What is the area typically covered by a tornado watch?

    <p>25,000 mi2</p> Signup and view all the answers

    What is the primary reason for issuing a tornado warning?

    <p>When a tornado has actually been sighted or is indicated by radar</p> Signup and view all the answers

    What is the typical duration of a tornado warning?

    <p>30 minutes to 1 hour</p> Signup and view all the answers

    Why are tornadoes difficult to forecast?

    <p>Because they are short-lived and don't last very long</p> Signup and view all the answers

    What is the result of advances in technology, communication, and improved forecasts?

    <p>A significant decline in tornado deaths</p> Signup and view all the answers

    What is the purpose of the Enhanced Fujita Intensity Scale (EF-Scale)?

    <p>To classify storms by assessing the damage produced</p> Signup and view all the answers

    What is the minimum water temperature required for hurricane formation?

    <p>80° F</p> Signup and view all the answers

    Why do hurricanes not form within 5° of the equator?

    <p>The Coriolis effect is too weak</p> Signup and view all the answers

    What is the term used to describe a tropical system with sustained wind speeds of less than 38 mph?

    <p>Tropical depression</p> Signup and view all the answers

    What is the main factor that determines the amount of damage caused by a hurricane?

    <p>Strength of the storm</p> Signup and view all the answers

    What is the name of the scale that ranks hurricanes based on their relative intensities?

    <p>Saffir-Simpson scale</p> Signup and view all the answers

    What happens to a hurricane when it moves over water that cannot supply warm, tropical air?

    <p>It weakens</p> Signup and view all the answers

    What is the term used to describe the rotation of a hurricane?

    <p>Cyclonic circulation</p> Signup and view all the answers

    What happens to the air density in a tropical disturbance when significant latent heat is released?

    <p>It decreases</p> Signup and view all the answers

    How many storms achieve tropical storm strength each year on average?

    <p>Between 80 and 100</p> Signup and view all the answers

    What is the term used to describe the diverging air in the upper layers of a hurricane?

    <p>Outflow</p> Signup and view all the answers

    What is the typical width of a storm surge?

    <p>40 to 50 miles</p> Signup and view all the answers

    What is the most intense side of the eye in the Northern Hemisphere?

    <p>Right side</p> Signup and view all the answers

    What type of structures are particularly susceptible to wind damage?

    <p>Mobile homes</p> Signup and view all the answers

    What can hurricanes also spawn?

    <p>Tornadoes</p> Signup and view all the answers

    What is the goal of monitoring and forecasting tropical system movement and intensity?

    <p>To provide timely watches and warnings</p> Signup and view all the answers

    Why are storm surges worse where the continental shelf is very shallow and gently sloping?

    <p>Because the water is shallower</p> Signup and view all the answers

    What can heavy rains and inland flooding affect?

    <p>Areas hundreds of miles from the coast</p> Signup and view all the answers

    What is used to monitor and forecast tropical system movement and intensity?

    <p>Satellite data, aircraft reconnaissance, coastal radar, and remote buoys</p> Signup and view all the answers

    Why are hurricane watches and warnings still issued for relatively large coastal areas?

    <p>To protect lives</p> Signup and view all the answers

    What is the term used to describe the rotating column of air in a tornado?

    <p>Mesocyclone</p> Signup and view all the answers

    What denotes the characteristic properties of an air mass?

    <p>Humidity and temperature</p> Signup and view all the answers

    Which type of air mass originates over land and is typically dry?

    <p>Continental Tropical</p> Signup and view all the answers

    How are air masses categorized based on their characteristics?

    <p>By their source area and surface nature</p> Signup and view all the answers

    What is the typical temperature characteristic of an Arctic air mass?

    <p>Very cold</p> Signup and view all the answers

    Which scenario is most likely associated with Continental Polar air masses?

    <p>Snowstorms in fall and winter</p> Signup and view all the answers

    What defines a Continental Arctic air mass?

    <p>Originates in high latitudes and is dry</p> Signup and view all the answers

    Which region is most affected by lake-effect snows caused by Continental Polar air masses?

    <p>Buffalo and Rochester, NY</p> Signup and view all the answers

    What type of air mass is typically humid and originates over water?

    <p>Maritime Polar</p> Signup and view all the answers

    Which type of air mass is primarily responsible for the precipitation received by the eastern two-thirds of the United States?

    <p>Maritime Tropical (mT)</p> Signup and view all the answers

    What characterizes a warm front?

    <p>Small slope and light-to-moderate precipitation</p> Signup and view all the answers

    What happens when two air masses clash at a front?

    <p>The warmer air mass is forced aloft</p> Signup and view all the answers

    Which front is represented on a weather map with blue triangles extending into warmer air?

    <p>Cold Front</p> Signup and view all the answers

    What is the pressure gradient effect at a front?

    <p>Results in one air mass moving faster than the other</p> Signup and view all the answers

    Which type of front does NOT move?

    <p>Stationary Front</p> Signup and view all the answers

    What type of front occurs when a cold front overtakes a warm front?

    <p>Occluded Front</p> Signup and view all the answers

    Where do midlatitude cyclones primarily develop?

    <p>Along a front where air masses are parallel</p> Signup and view all the answers

    What is indicated by the 'L' symbol on a weather map?

    <p>Low-pressure center</p> Signup and view all the answers

    What is necessary for a tropical system to be classified as a hurricane?

    <p>Sustained winds in excess of 74 mph</p> Signup and view all the answers

    Which feature surrounding a hurricane's center experiences the highest winds and heaviest precipitation?

    <p>The eye wall</p> Signup and view all the answers

    What is the primary energy source for hurricanes?

    <p>Latent heat released from forming clouds</p> Signup and view all the answers

    What role does Doppler radar play in tornado detection?

    <p>It enhances the accuracy of tornado warnings through motion detection.</p> Signup and view all the answers

    Which of the following is true regarding the eye of a hurricane?

    <p>It is typically around 12.5 miles in diameter.</p> Signup and view all the answers

    Which of the following best describes hurricanes compared to mid-latitude systems?

    <p>They do not require fronts for formation.</p> Signup and view all the answers

    What is the lowest recorded pressure in an Atlantic basin hurricane?

    <p>882 millibars</p> Signup and view all the answers

    How does air pressure change from the outer edge of a hurricane to its center?

    <p>It drops from 1010 millibars to 950 millibars.</p> Signup and view all the answers

    Identifying tropical cyclones often requires knowledge of their geographical naming conventions. What is a hurricane known as in the western Pacific?

    <p>Typhoon</p> Signup and view all the answers

    What is a common consequence of the most powerful hurricanes?

    <p>They often cause significant loss of life and financial devastation.</p> Signup and view all the answers

    What is the average diameter of a mid-latitude cyclone?

    <p>1,000 miles</p> Signup and view all the answers

    What is the typical wind direction after the passage of a cold front?

    <p>Northerly</p> Signup and view all the answers

    What type of air mass is associated with air-mass thunderstorms?

    <p>Maritime tropical</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a mid-latitude cyclone?

    <p>Surface divergence</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a thunderstorm?

    <p>Strong inward spiral of wind</p> Signup and view all the answers

    What happens to the warm sector of a mid-latitude cyclone as the cold front catches up to the warm front?

    <p>The warm sector is lifted aloft</p> Signup and view all the answers

    What is the primary factor that drives the development of mid-latitude cyclones?

    <p>Upper-level air flow</p> Signup and view all the answers

    What are the typical weather conditions associated with a warm front?

    <p>Light precipitation, southerly winds, and warmer temperatures</p> Signup and view all the answers

    How do mid-latitude cyclones typically move across the United States?

    <p>From west to east</p> Signup and view all the answers

    What is the primary difference between a thunderstorm and a mid-latitude cyclone?

    <p>Thunderstorms have strong updrafts and downdrafts, while mid-latitude cyclones have a consistent inward spiral of wind</p> Signup and view all the answers

    Study Notes

    Air Masses

    • Air masses are vast bodies of air (typically 1000 miles across) with uniform temperature and moisture at given altitudes.
    • Small variations exist within air masses due to their extensive latitudinal reach (up to 20°).
    • A source area is where an air mass gains its temperature and moisture characteristics.
    • Air masses are classified by origin:
      • Arctic (A): Very cold, from high latitudes.
      • Polar (P): Cold, from high latitudes.
      • Tropical (T): Warm, from low latitudes.
    • Surface nature classification:
      • Continental (c): Formed over land, usually dry.
      • Maritime (m): Formed over water, usually humid.
    • Five primary air mass types:
      • Continental Arctic (cA): Very cold, from northern Canada.
      • Continental Polar (cP): Cold, from northern Canada and Alaska.
      • Continental Tropical (cT): Warm, from the Southwestern U.S. and Mexico.
      • Maritime Polar (mP): Develops from chilled Siberian air and North Atlantic.
      • Maritime Tropical (mT): Source of most eastern U.S. precipitation, comes from warm waters.

    Fronts

    • Fronts are boundaries separating air masses of differing densities, often characterized by temperature and moisture differences.
    • Typically relatively narrow (9 to 120 miles wide) with low-angle slopes at the frontal surface.
    • Four types of fronts:
      • Warm Fronts: Warm air replaces cold air; slower-moving with light-to-moderate precipitation.
      • Cold Fronts: Cold air advances; features heavier and more violent weather, moves faster than warm fronts.
      • Stationary Fronts: Both air masses flow parallel to the front with no movement.
      • Occluded Fronts: Cold fronts overtake warm fronts, causing complex weather patterns.

    Midlatitude Cyclones

    • Major weather systems between southern Florida and Alaska indicated by an "L" on weather maps.
    • Form where air masses move parallel and opposite to a front, typically containing cP air north and mT air south.
    • Development follows these stages:
      • Frontal surface shapes to a wave, low pressure at the apex.
      • Counterclockwise cyclonic circulation occurs.
      • A warm front and cold front form, with the cold front eventually occluding the warm front.
    • Move eastward across the U.S., causing significant weather contrasts, especially in spring.
    • Weather changes observed with warm front approach include lower clouds and light precipitation; cold front brings heavy precipitation and potential severe storms.

    Thunderstorms

    • Defined as storms producing lightning, thunder, gusty winds, heavy rainfall, and hail.
    • Formed from warm, moist air rising in unstable environments, categorized into:
      • Air-mass thunderstorms: Typically short-lived; form on warm summer days.
      • Severe thunderstorms: Associated with lifting air along fronts; can produce high winds and tornadoes.
    • Approximately 2,000 thunderstorms occur globally at any given time; the U.S. averages over 100,000 annually.
    • Required conditions for storms include warm, moist air and ongoing supply from the ground.

    Tornadoes

    • Violent windstorms characterized as rotating columns of air, with pressure in the storm lower than surroundings.
    • Max wind speeds can exceed 300 mph.
    • Form in severe thunderstorms, particularly supercells with strong updrafts.
    • In the U.S. (1992-2002), an average of 57 fatalities per year; notable spikes in severe tornado events like April 2011.
    • Tornado characteristics include:
      • Average diameter of 500 to 2,000 feet, traveling at ~30 mph with a lifespan around 6 minutes.
      • Most common in the central U.S., particularly during spring when contrasting air masses collide.
    • Severe tornadoes may last over 3 hours and can exceed 90 miles in length, causing significant destruction.### Tornadoes
    • Tornado destruction correlated with wind speed; can propel objects like straw through wood.
    • Urban areas face significant damage due to population density and wind speed.
    • Enhanced Fujita Intensity Scale (EF-Scale) classifies tornadoes based on damage, not direct wind speed.
    • Most tornado fatalities are due to flying debris; less than 2% of tornadoes result in fatalities.
    • 63% of tornadoes rated EF-0 or EF-1, whereas only 2% are EF-4 or EF-5, which account for 70% of deaths.
    • Tornadoes are difficult to forecast due to their short lifespan; watches and warnings are crucial for safety.
    • The Storm Prediction Center (SPC) issues multiple severe weather outlooks daily, assessing storm risk.
    • Tornado watches cover approx. 25,000 square miles for 4-6 hours when conditions are favorable for tornadoes.
    • Tornado warnings are localized alerts issued when a tornado is sighted or indicated, typically lasting 30 minutes to 1 hour.
    • Doppler radar enhances tornado tracking, detecting precipitation and wind motion; however, not all tornadoes show clear radar signatures.

    Hurricanes

    • Hurricanes are low-pressure systems forming over tropical waters, requiring sustained winds of 74 mph or more.
    • Energy for hurricanes comes from latent heat released during cumulonimbus cloud formation.
    • Most hurricane-related fatalities are from powerful storms like Katrina (2005) and Sandy (2012).
    • Typically form between 5° and 20° latitudes, with names varying by region: typhoons (Western Pacific) and cyclones (Indian Ocean).
    • Classification as a hurricane requires sustained winds > 74 mph; hurricanes average 375 miles across.
    • Central pressure can drop from 1010 to 950 millibars, with Hurricane Wilma holding the lowest recorded Atlantic pressure.
    • The eye wall, formed by rising warm moist air, has the highest winds; the eye, around 12.5 miles in diameter, exhibits lighter conditions.
    • Stronger hurricanes develop in warm waters (≥ 80°F) and generally do not form close to the equator due to weak Coriolis effect.
    • Development stages include tropical disturbances, tropical depressions (≤ 38 mph), and tropical storms (38-74 mph).
    • Saffir-Simpson scale ranks hurricanes from Category 1 to Category 5 based on intensity, with Category 5 being rare.

    Hurricane Damage

    • Damage is categorized into storm surge (causing most deaths), wind damage, and heavy rains/inland flooding.
    • Storm surge can extend 40-50 miles and is most severe on the right side of the storm; it dramatically increases in shallow continental shelf areas.
    • Wind damage results in projectiles and particularly affects mobile homes and high-rise buildings.
    • Hurricanes can spawn tornadoes, with over half producing at least one upon landfall.
    • Modern meteorology utilizes satellites, aircraft, coastal radar, and computer models to forecast hurricane movements and provide timely warnings.
    • Improved track forecasts are vital for assessing storm characteristics and enhancing safety measures.

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    Learn about air masses, characterized by similar temperature and moisture at any given altitude, and how they affect weather patterns and severe weather.

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