1. Ch 17 Section 2 Weather

2. Atmospheric pressure Atmosphere presses down on you with the equivalent to one kilogram per square centimeter. Pressure is caused by gas molecules colliding with each other and your skin. Pressure decrease as altitude increases Air is thinner in upper atmosphere Oxygen decreases as altitude increases Air planes are pressurized due to this decrease

3. Global winds and pressure systems Weather patterns result from complex global patterns of wind and pressure. Westerlies- winds that blow from the west in the middle latitudes Tradewinds blow from the east in the tropics

4. Jetstreams Jetstreams control many weather processes, such as storm development. 12 km above surface Can travel 500km/h Moves north and south with seasons

5. High and Low pressure systems Subtropical Highs are relatively stable belts of high pressure near latitudes of 30°.

6. Coriolis Effect When air rises with low pressure and sinks with high pressure systems.

7. Air Masses and Weather Fronts Air masses can be polar or tropical and continental or maritime. Air masses interact in zones called weather fronts. Warm and cold fronts create different types of precipitation.

8. Thunderstorms A cumulonimbus cloud can have ice crystals at the top of the cloud can sometimes form hail.

9. Downdrafts and Squalls The falling rain can sometimes bring cool air with it; the sinking air current is called a downdraft. When a downdraft hits the earth’s surface and spreads out as windy gusts; it is called a squall.

10. Downbursts When downdrafts hit the surface and spread out very violently. Wind can reach speeds of 260 km/h

11. Tornadoes Intense, short-lived, violent, localized storms that occur in the mid latitudes.

12. Tornadoes Can move at speeds of 50 km/h across surface Wind speeds in funnel can reach 400 km/h

13. Hurricanes Tropical storms that cover vast areas and last for days At 118 km/h winds; tropical depression is upgraded to hurricane. Western pacific hurricanes are called Typhoons.