Q. In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason?

• Sea surface temperatures are low
• Inter-Tropical Convergence Zone seldom occurs
• Coriolis force is too weak
• Absence of land in those regions

Answer: (b) Inter-Tropical Convergence Zone seldom occurs

Reasons for the lack of cyclone formation in the South Atlantic

• Sea surface temperatures run a shade cooler than the one ideal for tropical cyclone formation.
• Climatologically high values of vertical wind shear across that basin throughout the year even in summer.
• Vorticity: Lack of pre-existing centres of rotation in the area.
• Absence of tropical waves.
• The Intertropical Convergence Zone (ITZC), which shifts toward the north in northern summer and toward the south in the southern summer, usually stays at or north of the equator.
• The tropospheric vertical wind shear is much too strong and there is typically no inter-tropical convergence zone (ITCZ) over the ocean.
• Without an ITCZ to provide synoptic vorticity and convergence resulting in large-scale spin and thunderstorm activity as well as having strong wind shear, it becomes very difficult to generate tropical cyclones.
• ITCZ stays at or near the equator and does not shift southward over the south Atlantic or South Pacific region. Therefore, these regions do not have the ITCZ over them which is a major cause of the lack of cyclones.
• Lower sea temperatures are also a reason.