Cyclones - Understanding Storm Systems

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1. What is a Cyclone? Types? Paths?
2. How do we recognize a cyclone?
3. What are Mid-latitude Cyclonic Systems?
4. What are their stages, from birth to dissipation?
5. What is the weather associated with the passage of a wave cyclone?

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Cyclones - Understanding Storm Systems

  1. 1. Storms SystemsWhat is a Cyclone? Types? Paths?How do we recognize a cyclone?What are Mid-latitude Cyclonic Systems?What are their stages, from birth todissipation?What is the weather associated with thepassage of a wave cyclone?
  2. 2. Cyclones What is a cyclone? Types of cyclones: •Wave Cyclone: mid & high latitudes •Tropical Cyclone: low latitudes •Tornado (small & very intense vortex)•Enclosed area of low pressure (mb)•Air circulation is into centre and up•Rotation = CCW-NH and CW-SH
  3. 3. How do we recognize a cyclone?Map of surface observations Satellite ImagesWind Barbs (speed & direction) Comma-shaped cloud mass Very Windy Calm http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cyclone_w nd.rxml?hret=/guides/mtr/cyc/def.rxml Midlatitude Cyclone
  4. 4. Mobile Storm Systems www.physicalgeography.net/fundamentals/7s.htmln arrowsWhat do you call the Cyclones shown as:  Green arrows?  Black arrows?
  5. 5. Daily World Weather Map
  6. 6. Mid-Latitude (Wave) Cyclone•Typically accompanied by fronts•They are leading edges of air masses•Wrapping around a centre of low pressure Why is it called a wave? What steers it? Pushing What generates its cyclonic motion? Transporting warm, moist air N Dragging colder, drier air S Pullinghttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cyc/def.rxml
  7. 7. Understanding the entire system… Mid-Latitude Cyclone. Horizontal extent? (1000-1500 km wide) Speed of Travel (entire system)? (50-60 km/h or 1200 km in a day) Direction of travel? (generally eastward) What is a typical lifespan? (3-10 days) Speed and Slope of the fronts? (Cold = 30-40 km/h and 1:50 or steeper) (Warm = 10-20 km/hr and 1:200)
  8. 8. Life Cycle of a Mid-latitude Cyclone What is Cyclogenesis? Atmospheric process in which low pressure wave cyclones develop and strengthen Initial Stage Open stage Occluded stage Dissolving stage
  9. 9. Life Cycle of a Mid-latitude Cyclone Initial Stage Stationary front b/t warm & cold air masses (at the polar front) Divergence aloft (at jet stream) causes air to rise Causes low pressure along front http://www.on.ec.gc.ca/skywatchers/swtc_d ocs/frontal_poster/front_weather_e.html
  10. 10. Life Cycle of a Mid-latitude Cyclone Open Stage Maturing depression Fronts develop• Cold, denser air pushing south• Undercuts warm, lighter air• = Lift • CCW funnels warm air towards centre • Pressure drops • Storm intensifies Cold air: advancing, retreating
  11. 11. Development of a Mid-latitude Cyclone Occluded Stage Cold front overtakes Warm front (forced aloft) Influx of warm air ↓’ed Pressure stops falling Gradually cools = Stop rising Mixes
  12. 12. Development of a Mid-latitude Cyclone Dissolving Stage System dissipates Lifting mechanisms is cutoff No source of energy and moisture
  13. 13. Midlatitude Cyclone Christopherson and Byrne 2009
  14. 14. Life Cycle of a Mid-latitude Cyclone http://science.jrank.org/pages/47861/middle-latitude-tropospheric-circulations.html  Can you identify the stages?  Can you differentiate the symbols?  Can you visualize it in cross-sectional view?
  15. 15. Last WednesdayToday
  16. 16. What is the weather associated with the passage of a wave cyclone?Two Fronts (boundaries) • Warm & Cold Front http://www.uwsp.edu/geo/faculty/ritter/geog101/textboThree Sectors of a wave cyclone: ok/weather_systems/weather_and_wave_cyclones.html a) cool sector ahead of the warm front b) warm sector between the cold and warm fronts c) cold sector located behind the cold front
  17. 17. To Interpret Weather, You need to think about…Pressure distribution (isobars) Where is the lowest pressure? From the east Gradient and V-shape From the northWind Direction Differ in the 3 sectors? From the southPrecipitation Where and Extent?
  18. 18. Weather, as the Wave Cyclone Passes…a) Cool Sector  Air Mass (cP)  Pressure Tendency (falling)  Wind Direction (E – SE)  Clouds (Cirrus–Nimbostratus)  Precipitation  At warm front • low intensity • long duration
  19. 19. Weather, as the Wave Cyclone Passes…b) Warm Sector  Air Mass (mT)  Pressure Tendency (rising-falling)  Wind Direction (SE–S-SW)  Clouds (Clring–Cumulonimbus)  Precipitation  At cold front • high intensity • long duration
  20. 20. Weather, as the Wave Cyclone Passes…c) Cold Sector  Air Mass (cP)  Pressure Tendency (rising)  Wind Direction (W-NW)  Clouds (Cumulonimus-Clring)
  21. 21. Life Cycle of a Mid-latitude CycloneCan you identify Initial, Open, Occluded, Dissolving Stages?

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