Which factor primarily determines whether a cold or warm occlusion occurs?

• A. Difference in surface humidity.
• B. Wind speed difference.
• C. Pressure changes.
• D. Difference in temperature within each frontal system.

Answer: (D)

The key factor is the temperature relationship between the air masses around the front. When a cold front overtakes a warm front, the type of occlusion depends on how cold the air behind the advancing cold front is compared with the air above the warm front. If the cold air behind the front is colder than the air over the warm front, the cold air undercuts the warm air and a cold occlusion forms. If the air behind the cold front is warmer than the air over the warm front, the warm air stays aloft and wraps around the cooler core, creating a warm occlusion. In short, the deciding factor is the difference in temperature within the frontal systems and how their vertical temperature structures interact at the boundary. Humidity, wind differences, or pressure changes can influence weather intensity, but they don’t determine the occlusion type.