Air Masses & Weather Fronts

Observations & Questions

• Presence of an 'H' over Georgia indicating a heatwave.
• Wondering about the significance of 'H' on weather maps.
• Questions on the nature and influence of air masses.

Definition of Air Mass

• Large body of air with distinct temperature and humidity.
• Bordered by weather fronts.
• Influences daily temperature and humidity changes.
• Characteristics determined by origin:
  • Polar (P): Mid-high latitudes (33-65°) - Cold
  • Tropical (T): Low latitudes (0-32°) - Warm

Classification of Air Masses

• Maritime (m): Originates over oceans, leading to humid conditions.
• Continental (c): Originates over land, leading to dry conditions.
• Arctic (A): High latitudes (66-90°) - Very cold

Jet Stream

• Fast-flowing air at the top of the troposphere.
• Wind speeds often exceed 100 mph.
• Forms at the boundary between Polar and Tropical air masses.
• Flows from west to east.

Weather Fronts

• Boundary between two air masses with different temperatures or humidity.
• Named after the air mass moving into the region.
• Analogous to a battlefront where different forces meet.

Identifying Weather Fronts

• Sharp temperature changes over short distances.
• Humidity changes.
• Rapid wind direction shifts.
• Pressure changes.
• Cloud and precipitation patterns.

Types of Weather Fronts

1. Warm Front

• Warm air mass overtakes a cold air mass.
• Associated with cirrus clouds, stratus/nimbostratus clouds.
• Results in prolonged overcast skies, light to moderate rain.

2. Cold Front

• Convergence of cold and warm air masses.
• Cumulonimbus clouds in warm air, leading to thunderstorms/heavy precipitation.
• Can cause severe weather like hail and tornadoes.

3. Occluded Front

• Occurs when a warm air mass is caught between two cold air masses.
• Mixture of clouds from both warm and cold fronts.
• Heavy rain in warm months, blizzards in cold months.

4. Stationary Front

• Cold and warm air masses move past each other in opposite directions.
• Stalemate in temperature and wind conditions.
• Extended cloudiness and/or light precipitation.
• Stratus clouds types present (stratus, alto stratus, cirro stratus, nimbo stratus).

Why Warm Air Lifts

• Temperature and humidity differences create varying densities.
• Warm, humid air is less dense, causing it to rise.

Demonstrations

• Various types of lifting mechanisms such as:
  • Orographic lifting
  • Frontal wedging
  • Convergence
  • Local convective lifting