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?

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

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. How do we recognize a cyclone?
Map of surface observations Satellite Images
Wind 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. Mobile Storm Systems
www.physicalgeography.net/fundamentals/7s.htmln arrows
What do you call the Cyclones shown as:
 Green arrows?
 Black arrows?

5. Daily World Weather Map

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
Pulling
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cyc/def.rxml

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. 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. 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. 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. 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. Development of a Mid-latitude Cyclone
Dissolving Stage
System dissipates
Lifting mechanisms
is cutoff
No source of energy
and moisture

13. Midlatitude
Cyclone
Christopherson and Byrne 2009

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. Last
Wednesday
Today

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. 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 north
Wind Direction
Differ in the 3 sectors?
From the south
Precipitation
Where and Extent?

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. 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. Weather, as the Wave Cyclone Passes…
c) Cold Sector
 Air Mass (cP)
 Pressure Tendency (rising)
 Wind Direction (W-NW)
 Clouds (Cumulonimus-Clring)

21. Life Cycle of a Mid-latitude Cyclone
Can you identify Initial, Open, Occluded, Dissolving Stages?