1. Mid-Latitude Weather Interacting air masses

2. Driving Energy Contrast Warm tropics vs. cool poles

3. Air Masses Latitude Surface Land Water TropicalArctic cT hot, dry cP cold, dry mT warm, moist mP cool, moist

4. Air Masses Tend to take the character of the source land Once formed, tropical masses move toward poles, polar masses move toward tropics

5. Fronts and Their Symbols Boundaries between air masses Designated by advancing mass Occluded front: purple triangles and semicircles, same side Stationary front: both, opposite sides Warm front: red semicircles Cold front: blue triangles

6. Mid-Latitude Cyclones Earth’s biggest storms

7. Air Mass Movement North-south trajectories deflected by Coriolis effect (to right in northern hemisphere) WARM COLD

8. A Cyclone is Born Diverging air masses create a boundary low L WARM COLD

9. Developing Cyclone Masses circle the low Cold mass faster than warm L WARMCOLD

10. Dying Cyclone Cold mass undercuts low center L WARMCOLD

11. Warm Front Weather WARMCOLD snow Frozen rain freezing rain rain

12. Cold Front Weather WARM COLD

13. Jet Stream Deflected to east by Coriolis effect warm cool High-altitude air movement

14. Jet Stream Initially runs at front boundary Can intensify updraft if over L center Meanders (“Rossby waves”) also affect vertical mixing trough Intensify updraft