Hurricane Origins: South Atlantic and South Pacific

Tropical Cyclone Basins: Where Hurricanes Form

Hurricanes (tropical cyclones) do not typically originate in the South Atlantic or South Pacific Oceans. They are overwhelmingly Northern Hemisphere phenomena.

Why Not the South Atlantic?

• Cooler sea surface temperatures (SSTs): Rarely reach 26.5°C threshold; Benguela Current upwelling cools eastern South Atlantic.
• Strong vertical wind shear: Disrupts storm organization.
• No ITCZ penetration: Intertropical Convergence Zone stays north of equator in Atlantic.
• Rare exceptions: Hurricane Catarina (2004, Brazil) — only recorded South Atlantic hurricane.

South Pacific

• Cyclones occur but are rare east of 160°E. Most form in Southwest Pacific (Coral Sea, near Australia, Vanuatu, Fiji) — called cyclones.
• Southeast Pacific: Extremely rare; cold Humboldt Current, high shear. No recorded hurricanes.

Primary Basins (Northern Hemisphere)

• North Atlantic: June–Nov; Caribbean, Gulf, US East Coast.
• Northeast Pacific: May–Nov; Mexico, Hawaii.
• Northwest Pacific: Year-round peak Aug–Oct; Philippines, Japan, China — called typhoons.
• North Indian Ocean: Apr–Dec; Bay of Bengal, Arabian Sea — called cyclones.

Formation Requirements

1. SST ≥ 26.5°C to 50 m depth.
2. Pre-existing disturbance (easterly wave, monsoon trough).
3. Low vertical wind shear (< 10 m/s).
4. Sufficient Coriolis force (> 5° latitude).
5. Mid-tropospheric moisture.

Southern Hemisphere basins lack consistent overlap of these factors.