1. Wind! Horizontal movement of air across surface
Pressure gradient force = pressure change over the distance it takes to change
Air flows from high to low pressure due to pressure gradient
Greater the pressure difference, stronger the wind
The unequal heating of Earth’s surface generates pressure differences. Solar radiation is the ultimate energy source for most wind.

2. Wind Instruments Wind direction is measured with a wind vane
Winds are named by where they come FROM
Ex. “Westerly” comes FROM the west
Wind speed is measured with an anemometer

3. Isobars Lines of equal pressure
Fastest winds occur when lines are closest together (pressure gradient increases)
High Pressure
Gradient

4. Pressure Systems
Winds blow TOWARD the center of a LOW pressure system (CONVERGENT)
Winds blow AWAY from the center of a HIGH pressure system (DIVERGENT)
Rising air (low pressure system) is associated with cloud formation and precipitation, whereas sinking air (high pressure system) produces clear skies.

5. DIVERGENT
CONVERGENT

6. 30.0
29.8
FASTEST
SPEED
29.6
NE WIND N W E S

7. 29.8
29.6
SW WIND
30.0 N W E
FASTEST
SPEED S

8. Pressure Systems L 29.8 FASTEST SPEED 29.6 30.0 Winds blow Toward
The center S

11. Observe the Jet Stream

13. What do these paths have in common?
You will remember these hurricanes from the Hurricane Tracking Lab that you completed back in September.
What do these paths have in common?

14. Watch Sandy at about 3:30

15. Why did Sandy turn sharply towards the west?