1. The Temperate Climate

2. The Temperate Hadley Cell Westerly Prevailing Winds Warm inputs (often from the Tropical Hadley Cell) Cold inputs form the Polar Hadley Cell Weather develops where the cold and warm inputs collide guided by the Jet Stream Westerly Prevailing Winds Warm inputs (often from the Tropical Hadley Cell) Cold inputs form the Polar Hadley Cell Weather develops where the cold and warm inputs collide guided by the Jet Stream

3. Weather Systems & Air Masses Weather System – recurring circulation pattern & associated weather Air mass – large bodies of air with uniform temp & moisture –Up to thousands of km across –May extend up to top of troposphere –Measured by: Temperature Humidity

4. Air Masses Develop over source regions Take on characteristics of the region Air masses classified by: –Latitude (Arctic (A), polar (P), tropical (T), equatorial (E)) Indicate temperature –Surface type (Maritime (m), continental (c)) Indicate moisture content

5. Source Regions Idealized continent & oceans show source regions for air masses Combined air mass labels (no cE, mA or mAA) –mE, mT, cT, mP, cP, cA, cAA

6. The Pineapple express Cold dry air from Alaska Warm moist air from Hawaii

8. Fronts Surface of contact between 2 distinct air masses –E.g. boundary between polar & tropical air → polar front

9. Fronts Cold air is heavier than warm air….the warm air is pushed over the cold air

10. Fronts Warm Front – moving front → warm air slides over cold air –Slower than cold front –Warm front stimulates nimbostratus clouds & rain

11. Cyclones Converging, inspiraling air rises → condensation Cyclonic storm: –Intense convection –Strong winds –Heavy precipitation 3 types of traveling cyclones: –Midlatitude cyclone (or extratropical cyclone) –Tropical cyclone –Tornado

12. Anticyclones High pressure Fair weather system Descending air warms adiabatically No condensation

13. A “Perfect Storm” Intense cyclonic storm L marks the center of rotation Strong wind & precip hit NE US (blue & orange) L L

14. Midlatitude Cyclones Dominant weather systems in mid & high latitudes Form, intensify and dissolve along polar front Air converging along front can create circulation Cyclone may last a few days, moving west-to- east

15. Lifecycle of Midlatitude Cyclone

16. Upper-Air Disturbances Closely related to midlatitude cyclone development at surface Upper-air convergence → high surface pressure Upper-air divergence → low surface pressure

22. Cyclone Tracks & Families Certain regions good to develop cyclones Upper-level winds consistently steer cyclones So, consistent cyclone tracks are well known Sets of tracks form cyclone families Midlatitude Cyclone Tracks

24. Cold Air Outbreaks Occasionally cold air from polar regions pushes far south This February image shows cold, clear air as far south as Florida White pattern E & SE of image is clouds from cold front White in NW of image is snow cover