Mid-latidtude Cyclones Flashcards
What temperature is the air behind a warm front?
Warm- overrides the cold air
What direction are cyclones in the Southern Hemisphere?
Clockwise
What is the diameter of M.C?
1000-4000km
Cyclogenesis
Development of cyclonic circulation in the atmosphere
What causes cyclogenesis?
An imbalance in energy between polar and tropical regions
What latitudes do M.C occur?
30°-60° North and South of the equator
What directions do M.C travel?
West to East at 40-90km/h
What are the conditions necessary for formation of M.C?
- 2 large high pressure cells in contact with a polar front
- warm, moist maritime airmass
- polar high-> cold, dry airmass
- air flow converges from either side of the polar front
- Disturbances result in unstable situation->creates local low pressure into which air will flow+around which air will circulate
What is the first stage of development?
INITIAL STAGE
- cold, dry easterly winds meet warmer moister westerlies at the polar front
- do not meet->move parallel to each other
- air masses retain own density and characteristics
What is the second stage of development?
GROWTH
- disturbance may occur on the polar front->causing clockwise rotation of air+development of a wave
- local decrease in air pressure
What is the third stage of development?
MATURE
- warm air moves to cold sector(and vice versa)
- warm air slides over cold dense air(cold/warm front develop)
- cold air forces warm air to rise->cumulonimbus clouds form
What is the fourth stage of development?
OCCLUSION
-cold front overtakes warm front-> forcing all warm air off the ground
What is the last stage of development?
DISSIPATION
- all warm air lifted high off the ground
- isobars become more even as low pressure degenerates
- upper winds break apart cloud cover
- rainfall stops
What is a cold front occlusion?
Air ahead of the advancing cold front is cool. Colder air wedges itself under cool air forcing it to rise
What is a warm front occlusion?
The air ahead of the warm front is colder than the air behind the advancing cold front. As cold air catches up with warm air, advancing cool air rises above the colder air ahead of the warm front.
