Air Masses and Their Types

Air Masses

• Air masses are large bodies of air with similar temperature and humidity.
• They travel long distances and influence local weather.
• Four major air masses impacting North America: Maritime Tropical, Continental Tropical, Maritime Polar, and Continental Polar.

Types of Air Masses

Maritime Tropical

• Warm, humid air mass.
• Forms over tropical oceans.
• In summer, brings showers and thunderstorms.
• In winter, brings heavy rain or snow.

Continental Tropical

• Hot, dry air mass.
• Forms over the Southwest.
• Covers the smallest area compared to other air masses.

Maritime Polar

• Cool, humid air mass.
• Forms over the Pacific and Atlantic oceans.
• Brings fog, rain, and cooler temperatures year-round.

Continental Polar

• Bitterly cold, low humidity air mass.
• Forms over Canada and Alaska.
• Winter = clear, cold, dry air.
• Summer = more mild.

How Air Masses Move

• Air masses move because of the prevailing westerlies and jet stream.
• These move air masses west to east.
• When air masses interact, there are weather changes.

Fronts

• Fronts are boundaries where air masses meet with different temperatures and humidities.
• Storms & changing weather occur along fronts.
• Four types of fronts:

Cold Fronts

• Dense, cold air slides under lighter warm air.
• Move quickly.
• Cause abrupt weather changes (e.g., thunderstorms).
• Cooler, drier air follows after the front passes.

Warm Fronts

• Less dense warm air pushes over cold air.
• Brings rainy/cloudy weather for days.
• Rain or snow occurs if air is humid
• Scattered clouds if air is dry
• After passing, weather is warm and humid.

Stationary Fronts

• When a warm and cold front meet but cannot move each other.
• Can bring many days of clouds and rain.

Occluded Fronts

• Warm air gets trapped between 2 cold air masses.
• Dense, cool air moves under both sides.
• Warm air is pushed up and cut off.
• As warm air rises, it condenses into precipitation.

Weather Forecasting

• Meteorologists use data from several sources to predict weather.
• Direct observations (looking at the sky/clouds) and instruments (weather balloons, satellites, barometers, weather stations) are used to gather data.
• Data is processed by computers to create weather maps and forecasts.

Reading Weather Maps

• Weather maps display weather conditions at a specific time over a large area.
• Weather service maps show data from many local weather stations.
• Symbols summarize data (e.g., high/low pressure, precipitation type, temperature).
• Isobars connect places with the same air pressure.
• Isotherms connect places with the same temperature.

Severe Weather

Thunderstorms

• Small storms with heavy precipitation, thunder, and lightning.
• Form in cumulonimbus clouds and typically along a cold front.

Hurricanes

• Tropical storms with winds of 73-198 mph.
• Form in the Atlantic, Pacific, and Indian Oceans.
• Common in August-October.
• Begin over warm water as low-pressure areas.
• Winds spiral inwards.
• Inside the storm are bands of clouds, high winds, & heavy rain.
• Last longer than other storms - several days

Tornadoes

• Fast spinning column of air reaching Earth's surface from a cumulonimbus cloud.
• Short-lived events or phenomena refer to occurrences that have a brief duration or lifespan. In meteorology, for example, short-lived weather patterns can include transient thunderstorms or quick-moving disturbances that develop rapidly and dissipate soon after. These types of weather events, while they can sometimes be intense, do not persist for long periods. Understanding the transient nature of short-lived weather is crucial for forecasting and preparing for sudden changes in atmospheric conditions, which can impact local environments and activities. and cover small areas.
• Form in thunderstorms.
• Can cause severe damage.
• Ranked using the Enhanced Fujita Scale.
• Common in "Tornado Alley" (Great Plains).

Snowstorms

• Year-round, most occur when the air is below 0°C or 32°F ground level.
• Starts as snow in the clouds; then falls to the ground.