Climate and Weather: Mid-Latitude Cyclones
Introduction
- Topic: Mid-Latitude Cyclones
- Importance: Understanding to apply knowledge, not just memorize.
- Key areas: Characteristics, formation conditions, stages, associated weather, impacts, case studies, synoptic map interpretation.
Definitions
- Alternate Names: Temperate cyclone, extratropical cyclone, frontal depression, wave cyclone.
- Common Exam Term: Mid-latitude cyclones.
- Low Pressure System: Found between 30-60 degrees latitude, north and south of the equator.
- Characteristics: Consists of a cold front and warm front.
Formation and Conditions
- ITCZ Influence: Moves south in Southern Hemisphere summer, north in winter, affecting pressure belts.
- Cold Fronts and Warm Fronts: Cold fronts affect South Africa mostly in winter due to high pressure belts moving north.
Cyclone Stages
- Initial Stage: Warm and cold air masses move parallel along the polar front.
- Wave Stage: Wave forms due to jet stream disturbances; circulation begins.
- Mature Stage: Cold front moves quickly, warm front moves gently; distinct separation between fronts.
- Occluded Stage: Cold front overtakes warm front, forming an occluded front.
- Dissipating Stage: Warm air uplifts entirely, cyclone dissipates.
Cross-Section Analysis
- Cold Front: Steep pressure gradient, rapid uplift, cumulonimbus clouds, heavy rainfall.
- Warm Front: Gentle gradient, gradual uplift, nimbostratus clouds, soaking rain.
Occluded Fronts
- Cold Front Occlusion: Cold air undercuts warm front.
- Warm Front Occlusion: Cold air passes over colder air ahead.
Weather Patterns and Impacts
- Synoptic Maps: High pressure belts' positions indicate seasonal changes, blocking or allowing cyclones.
- Cyclone Family: Multiple cyclones (e.g., a series of three) in an area.
Case Study: Impact on South Africa
- Western Cape: Cold fronts bring rain and strong winds; potential for floods and infrastructure damage.
- Positive Effects: Rain supports agriculture, tourism benefits from snow, overall economic benefits.
Conclusion
- Revision: Importance of synoptic map reading and past paper practice for deeper understanding.
These notes provide a structured summary of mid-latitude cyclones, encapsulating key aspects discussed in the presentation.