Extra Tropical Cyclones | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
EXTRA TROPICAL CYCLONES  
? The systems developing in the mid and high latitudes beyond the 
tropics are called the Middle Latitude or Extra tropical cyclones  
? The passage of front causes abrupt changes in the weather conditions 
over the area in the middle and high latitudes.  
? Extra tropical cyclones form along the polar front. Initially, the front 
is stationary. 
? In the northern hemisphere, warm air blows from the south and cold 
air from the north of the front.  
? When the pressure drops along the front, the warm air moves 
northwards and the cold air move towards south setting in motion an 
anticlockwise cyclonic circulation. 
? The surrounding air rushed in to occupy this void and coupled with the 
earth’s rotation, a cyclone is formed which advances with the 
westerlies (Jet Streams). 
?  The cyclonic circulation leads to a well developed extra tropical 
cyclone, with a warm front and a cold front . 
?  The warm air glides over the cold air and a sequence of clouds appear 
over the sky ahead of the warm front and cause precipitation.  
? The cold front moves faster than the warm front ultimately overtaking 
the warm front. The warm air is completely lifted up and the front is 
occluded and the cyclone dissipates. 
? So temperate cyclone is intense frontogenesis involving mainly 
occlusion type front. 
CHARACTERISTICS OF TEMPERATE CYCLONES 
? They stretch over 500 to 600 km. 
? They may spread over 2500 km 
? They have a height of 8 to 11 km. 
? The wind velocity increases with the approach but decreases after the 
cyclone has passed. 
Page 2


 
EXTRA TROPICAL CYCLONES  
? The systems developing in the mid and high latitudes beyond the 
tropics are called the Middle Latitude or Extra tropical cyclones  
? The passage of front causes abrupt changes in the weather conditions 
over the area in the middle and high latitudes.  
? Extra tropical cyclones form along the polar front. Initially, the front 
is stationary. 
? In the northern hemisphere, warm air blows from the south and cold 
air from the north of the front.  
? When the pressure drops along the front, the warm air moves 
northwards and the cold air move towards south setting in motion an 
anticlockwise cyclonic circulation. 
? The surrounding air rushed in to occupy this void and coupled with the 
earth’s rotation, a cyclone is formed which advances with the 
westerlies (Jet Streams). 
?  The cyclonic circulation leads to a well developed extra tropical 
cyclone, with a warm front and a cold front . 
?  The warm air glides over the cold air and a sequence of clouds appear 
over the sky ahead of the warm front and cause precipitation.  
? The cold front moves faster than the warm front ultimately overtaking 
the warm front. The warm air is completely lifted up and the front is 
occluded and the cyclone dissipates. 
? So temperate cyclone is intense frontogenesis involving mainly 
occlusion type front. 
CHARACTERISTICS OF TEMPERATE CYCLONES 
? They stretch over 500 to 600 km. 
? They may spread over 2500 km 
? They have a height of 8 to 11 km. 
? The wind velocity increases with the approach but decreases after the 
cyclone has passed. 
 
? Jet stream plays a major role in temperate cyclonogeneis. 
? Jet streams also influence the path of temperate cyclones. 
? Since these cyclones move with the westerlies (Jet Streams), they are 
oriented east-west.