Weather Chapters 12 &13
Air Masses <ul><li>Large body of air that takes on the charateristics of the area where it was formed (over land masses ar...
 
Wind Systems <ul><li>Coriolis Effect- Earth’s rotation causes wind patterns </li></ul><ul><ul><li>N. Hemisphere   wind to...
 
Fronts <ul><li>Narrow region separating 2 air masses of different densities (temperatures) </li></ul><ul><li>Cold front </...
Fronts- Cont’d <ul><li>Warm Front-  </li></ul><ul><ul><li>Warm air pushes cold air (slowly) upwards   gradual slope </li>...
Fronts-Cont’d <ul><li>Stationary- two air masses meet and neither forces the other out (temperature (density) difference b...
Pressure Systems <ul><li>High Pressure- air sinks (few clouds) and spreads out; circulates in RIGHT in N Hemis. </li></ul>...
Cyclone (Nor'easter) <ul><li>Develops along a stationary front   imbalance (temp, pressure, density) causing part of the ...
Measuring Weather <ul><li>Thermometer- measures temperature </li></ul><ul><li>Barometer- measures air pressure </li></ul><...
Thunderstorms <ul><li>Formation </li></ul><ul><ul><li>1. Need abundant source of moisture in lower atmosphere </li></ul></...
Types of Thunderstorms <ul><li>Air Mass- caused by unequal heating (late afternoon thunderstorms) </li></ul><ul><ul><li>Mo...
Development <ul><li>1. Cumulus- air rises vertically   creating updrafts- moisture at the top of cloud </li></ul><ul><li>...
 
Severe T-storms <ul><li>Super cells- cold front powers updrafts </li></ul><ul><li>10 % of all T-storms </li></ul><ul><li>H...
Lightning <ul><li>Caused by friction between updrafts and downdrafts </li></ul><ul><ul><li>Positive and negative ions form...
 
Tornadoes <ul><li>Violent, whirling wind column of air with contact to ground </li></ul><ul><ul><li>Often associated with ...
Hurricanes <ul><li>Tropical cyclone- large, rotating low pressure system </li></ul><ul><ul><li>Form b/c large amount of en...
Stages <ul><li>1. traveling tropical disturbance </li></ul><ul><li>2. Circulation </li></ul><ul><li>3. Winds of 65 km/hr ...
 
Hurricane Hazards <ul><li>Storm surge- hurricane force winds drive ocean waters inwards sometimes 6 m higher than usual </...
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Weather Lecture

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Weather Lecture

  1. 1. Weather Chapters 12 &13
  2. 2. Air Masses <ul><li>Large body of air that takes on the charateristics of the area where it was formed (over land masses are drier) </li></ul><ul><li>Classifying air masses </li></ul><ul><ul><li>Temperature </li></ul></ul><ul><ul><ul><li>Polar (P), Tropical (T) </li></ul></ul></ul><ul><ul><li>Location </li></ul></ul><ul><ul><ul><li>Continental (c), Maritime (m), Arctic (a) </li></ul></ul></ul>
  3. 4. Wind Systems <ul><li>Coriolis Effect- Earth’s rotation causes wind patterns </li></ul><ul><ul><li>N. Hemisphere  wind to right </li></ul></ul><ul><ul><li>S. Hemisphere  wind to the left </li></ul></ul><ul><li>Polar Easterlies (Westerlies)- 60 °- poles- NE in N Hemis.; SW in S Hemis. </li></ul><ul><li>Prevailing Westerlies- 30-60°- westward winds </li></ul><ul><li>Trade winds- 30-0° - Easterlies </li></ul><ul><li>Intertropical Convergence Zone- “doldrums”- rising air causes frequent rain  rain forests (near equator) </li></ul><ul><li>Jet streams- high altitude winds, move weather patterns </li></ul>
  4. 6. Fronts <ul><li>Narrow region separating 2 air masses of different densities (temperatures) </li></ul><ul><li>Cold front </li></ul><ul><ul><li>Cold dense air, displaces (pushes) warn air up along STEEP front; as warm air rises it condenses  showers, clouds </li></ul></ul><ul><ul><li>Larger temperature differences  more “powerful” cold front </li></ul></ul>
  5. 7. Fronts- Cont’d <ul><li>Warm Front- </li></ul><ul><ul><li>Warm air pushes cold air (slowly) upwards  gradual slope </li></ul></ul><ul><ul><li>Very cloudy, precipitation </li></ul></ul>
  6. 8. Fronts-Cont’d <ul><li>Stationary- two air masses meet and neither forces the other out (temperature (density) difference between them is very small)  cloudy </li></ul><ul><li>Weather doesn't change until another front comes through </li></ul>
  7. 9. Pressure Systems <ul><li>High Pressure- air sinks (few clouds) and spreads out; circulates in RIGHT in N Hemis. </li></ul><ul><li>Low pressure- air rises  replaced  in and upward motion (LEFT in N hemis.) </li></ul>
  8. 10. Cyclone (Nor'easter) <ul><li>Develops along a stationary front  imbalance (temp, pressure, density) causing part of the front to move south as Warm front moves North  upper and lower level winds must be favorable fro a low pressure cyclone to form </li></ul>
  9. 11. Measuring Weather <ul><li>Thermometer- measures temperature </li></ul><ul><li>Barometer- measures air pressure </li></ul><ul><li>Anemometer- measures wind speed </li></ul><ul><li>Hygrometer measures humidity </li></ul><ul><li>Radar </li></ul><ul><li>Infrared- temperature sensitive assists with measuring cumulonimbus clouds </li></ul>
  10. 12. Thunderstorms <ul><li>Formation </li></ul><ul><ul><li>1. Need abundant source of moisture in lower atmosphere </li></ul></ul><ul><ul><li>2. Air lifting  allows for condensation </li></ul></ul><ul><ul><li>3. unstable atmosphere </li></ul></ul><ul><li>Limitations </li></ul><ul><ul><li>1. Rising air meets stable air </li></ul></ul><ul><ul><li>2. Rate of condensation not able to keep cloud warmer than air (limits cumulonimbus to 18,000 m) </li></ul></ul>
  11. 13. Types of Thunderstorms <ul><li>Air Mass- caused by unequal heating (late afternoon thunderstorms) </li></ul><ul><ul><li>Mountain T-storms- orographic lifting </li></ul></ul><ul><ul><li>Sea-breeze T-storms- extreme temp differences at shore </li></ul></ul><ul><li>Frontal- mostly advancing cold fronts- rapid upward flow  line of T-storms at leading edge </li></ul>
  12. 14. Development <ul><li>1. Cumulus- air rises vertically  creating updrafts- moisture at the top of cloud </li></ul><ul><li>2. Mature- precipitation forces air under cloud to cool  creates downdraft </li></ul><ul><li>3. Dissipation– downdrafts cool surrounding air  no steady, warm moist air </li></ul>
  13. 16. Severe T-storms <ul><li>Super cells- cold front powers updrafts </li></ul><ul><li>10 % of all T-storms </li></ul><ul><li>Hail- frozen layered precipitation </li></ul>
  14. 17. Lightning <ul><li>Caused by friction between updrafts and downdrafts </li></ul><ul><ul><li>Positive and negative ions form </li></ul></ul><ul><ul><li>Stepped leader[-] (invisible) extends towards ground </li></ul></ul><ul><ul><li>Return stroke [+] reaches up to meet stepped leader </li></ul></ul><ul><ul><li>When they meet channel forms lightning bolt </li></ul></ul><ul><li>Thunder- sound caused by rapid expansion/contracting of air </li></ul>
  15. 19. Tornadoes <ul><li>Violent, whirling wind column of air with contact to ground </li></ul><ul><ul><li>Often associated with Super cells </li></ul></ul><ul><ul><li>Caused by a sudden change in wind speed/direction  wind shear </li></ul></ul><ul><ul><li>Causes horizontal swirling winds near ground </li></ul></ul><ul><ul><li>Interaction with updrafts force tornado upright </li></ul></ul><ul><ul><li>More likely in Spring and late afternoon/evening </li></ul></ul><ul><ul><ul><li>Spring b/c of clash of polar and maritime air over Great Plains </li></ul></ul></ul>
  16. 20. Hurricanes <ul><li>Tropical cyclone- large, rotating low pressure system </li></ul><ul><ul><li>Form b/c large amount of energy and moisture join with a tropical disturbance </li></ul></ul><ul><ul><li>Pressure decreases at center causing circulation (low pressure) </li></ul></ul><ul><li>Needs: </li></ul><ul><ul><li>1. Abundance of very warm water </li></ul></ul><ul><ul><li>2. Disturbance to lift warm air </li></ul></ul>
  17. 21. Stages <ul><li>1. traveling tropical disturbance </li></ul><ul><li>2. Circulation </li></ul><ul><li>3. Winds of 65 km/hr  tropical storm </li></ul><ul><li>4. Winds of 120 km/hr  hurricane </li></ul><ul><ul><li>Eye development </li></ul></ul><ul><ul><li>Eye wall- highest winds </li></ul></ul><ul><li>5. decline- after landfall  no water supply </li></ul>
  18. 23. Hurricane Hazards <ul><li>Storm surge- hurricane force winds drive ocean waters inwards sometimes 6 m higher than usual </li></ul><ul><li>Flooding </li></ul><ul><li>Wind </li></ul><ul><li>Rain </li></ul>

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