Q. In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (UPSC Prelims 2015)
Answer: Inter-Tropical Convergence Zone seldom occurs
Notes: Tropical cyclones require a specific set of environmental conditions to form, including high sea surface temperatures, atmospheric instability, and a pre-existing disturbance. The South Atlantic and South-Eastern Pacific are notable exceptions where these storms are extremely rare.

• ITCZ Positioning (Option B – Correct): The Inter-Tropical Convergence Zone (ITCZ) is the region where the Northern and Southern Hemisphere trade winds meet, creating the rising air and "disturbances" necessary to trigger a cyclone. In the South Atlantic and South-Eastern Pacific, the ITCZ rarely shifts far enough south of the equator. Without the ITCZ to provide the initial "seed" or low-pressure disturbance, cyclones cannot develop.
• Sea Surface Temperatures (Option A – Incorrect): While these regions do have cooler waters due to upwelling (like the Peru Current and Benguela Current), temperature is only part of the story. Parts of these oceans do reach the required 26.5°C threshold at times, yet cyclones still fail to form primarily due to atmospheric factors.
• Coriolis Force (Option C – Incorrect): The Coriolis force is a function of latitude. It is strongest at the poles and zero at the equator. Since these regions are in "tropical latitudes" (away from the immediate equator), the Coriolis force is technically sufficient to induce rotation; it is the lack of a disturbance that prevents it.
• Vertical Wind Shear (Additional Factor): Though not an option here, these regions also experience high vertical wind shear. Strong winds at different altitudes "rip" the developing storm apart before it can organize.

The lack of the ITCZ, combined with high vertical wind shear and relatively cooler sea surfaces, makes these regions "cyclone-free" zones compared to the North Atlantic or the Western Pacific.