Lecture Notes: Climate and Weather - Mid-Latitude Cyclones
Key Topics Covered:
- General characteristics of mid-latitude cyclones
- Areas and conditions of formation
- Stages of formation
- Associated weather phenomena
- Identification on synoptic maps
- Environmental impacts
- Case study and management strategies
General Characteristics:
- Also known as: temperate cyclone, extratropical cyclone, frontal depression, wave cyclone.
- Commonly used term: mid-latitude cyclones.
- Low-pressure systems occurring in mid-latitudes (30-60 degrees).
- Occurs north and south of the equator.
- Characterized by a cold front and a warm front.
Conditions and Areas of Formation:
- Affected by the Inter-Tropical Convergence Zone (ITCZ) position.
- In southern hemisphere summer, ITCZ moves south; winter, it moves north.
- High-pressure systems affect the movement and impact of cyclones.
Stages of Cyclone Formation:
- Initial Stage: Polar front with warm and cold air moving parallel.
- Wave Stage: Disturbance along the polar front due to jet streams.
- Mature Stage: Defined cold and warm fronts, heaviest rainfall at cold front.
- Occluded Stage: Cold front overtakes warm front, forming an occluded front.
- Dissipating Stage: All warm air uplifted, cyclone dissipates.
Weather Associated with Cyclones:
- Cold Front: Rapid uplift of warm air, cumulonimbus clouds, heavy rainfall.
- Warm Front: Gentle uplift, nimbostratus clouds, soaking rain.
Occlusion Types:
- Cold Front Occlusion: Cold air undercuts warm front.
- Warm Front Occlusion: Cooler air overrides colder air.
Synoptic Map Interpretation:
- Identify cloud patterns and movements.
- Position of high-pressure systems indicates season (summer or winter).
Environmental Impact:
- Can bring strong winds and heavy rainfall.
- Potential for flooding, especially in Western Cape.
- Positive impacts include water supply, agriculture benefits, snow tourism.
Management Strategies:
- Monitoring synoptic maps and satellite images.
- Taking precautionary measures against heavy rains and winds.
Case Study: Western Cape
- Cold fronts bring rains, winds, and floods.
- Gale force winds and high seas can occur.
- Can cause damage but also support agriculture and tourism.
Note: These notes are based on a detailed lecture on mid-latitude cyclones, focusing on their formation, impact, and identification on weather maps.