jet streams/cyclones

Upper-Level Winds

Predominant Upper-Level Winds

  • Polar Front Jet Stream

  • Subtropical Jet Stream

Existence Factors

  • Differences in heights and temperature (cold vs. warm)

Low Tropospheric Wind Systems

  • Transition to lower-level wind systems

Monsoons

  • Definition of Monsoon: Seasonal wind reversal

  • Key Terms:

    • Thermally Induced: Caused by uneven heating of land and water

  • Characteristics: Wind reversals result from different heat absorption rates between land and water

Example: Southeast Asia

  • Southeast Asia is noted for having the strongest monsoon on Earth.

  • U.S. Monsoon Areas: Arizona experiences a type of monsoon, though not as pronounced as in Southeast Asia.

Wind Patterns in Southeast Asia

  • Winter Winds:

    • Offshore flow characterized by wind blowing from land to sea.

    • High pressure (H) over land due to colder air, and low pressure (L) over warmer ocean water leads to wind patterns.

  • Spring/Summer Winds:

    • Reversal to onshore flow as land heats faster than water, resulting in lower pressures over land and higher pressures over ocean.

Implications of Onshore Flow

  • Onshore winds bring hot, humid air from the ocean, leading to increased moisture and potential for heavy rainfall, especially in the presence of geographical features like the Himalayan Mountains.

Effects of Monsoonal Flow

  • Heavy Precipitation:

    • Can exceed 120 inches monthly during peak monsoon season.

  • Geographic Impact: Areas like Bangladesh are prone to severe flooding, causing loss of life and property.

  • Historical Example: In the 1980s, over 250,000 people died in flooding events in Bangladesh.

Daily Wind Reversals: Sea Breezes

  • Sea breezes operate on a daily cycle instead of a seasonal one.

  • Mechanism:

    • During the day, land heats up and creates a low-pressure area while the ocean remains cooler.

    • Wind changes direction from offshore (morning) to onshore (afternoon), bringing moisture.

Sea Breeze Dynamics

  • Morning Conditions:

    • Offshore flow while land cools overnight leads to low moisture chances.

  • Afternoon Conditions:

    • As land heats up, onshore flows develop, increasing humidity and cloud cover.

Case Study: Florida

  • Thunderstorms often develop due to convergence caused by the onshore flow.

    • Severe weather events including hail or tornadoes can occur.

    • Forecasting is crucial during summer months for impacts on tourism and activities.

Jet Streams and Cyclogenesis

  • Understanding jet streams is essential for weather prediction.

  • Jet Stream Characteristics:

    • High-speed wind currents (~80-100 mph) vary significantly and can disrupt atmospheric balance.

  • History:

    • The understanding of jet streams developed with advancements in aircraft technology during WWII.

Air Masses and Fronts

  • Definition of Air Mass:

    • A large body of air with uniform temperature and moisture properties.

  • Formation:

    • Air masses take on characteristics of the surface below them, whether it be land or ocean.

Types of Air Masses

  • Example: Arctic air masses are cold and dry, while tropical oceanic air masses are warm and humid.

Fronts and Weather

  • Boundaries between differing air masses lead to weather changes.

  • Understanding fronts helps in weather prediction and analysis of severe weather phenomena.

Future Topics

  • Upcoming discussions will include cyclogenesis, low-level jets, and severe weather patterns.

  • Importance of recognizing jet stream patterns for predicting warm and cold fronts.

Conclusion

  • Review of upper and low tropospheric winds has implications for understanding global weather systems and preparing for severe weather.

  • Importance of continuous learning about atmospheric processes and their real-world impacts on communities and environments.