Why in the News?

The India Meteorological Department (IMD) has forecast the intensification of a deep depression into Cyclone Fengal, set to affect Tamil Nadu over the next two days. This will be the second cyclone of the post-monsoon season, following Cyclone Dana. The storm, named Fengal by Saudi Arabia, is likely to bring heavy to extremely heavy rainfall, prompting a red alert for Tamil Nadu on Wednesday and an orange alert on 28th November 2024.

What are Cyclones?

• Cyclones are violent circular storms characterized by low-pressure centers and high-speed winds, originating over warm tropical oceans. These storms bring destructive winds (squalls), heavy rainfall (torrential), and storm surges, causing large-scale devastation, especially in coastal areas.
• Key Features:
  • Circulation: Cyclonic winds rotate anti-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere due to the Coriolis effect.
  • Structure: Cyclones feature an "eye" at the center, surrounded by an "eye wall" of intense winds and rain, with spiral rain bands extending outward.
  • Size and Path: Compact in size (80–300 km near the center) but may extend up to 1500 km. They follow a parabolic path influenced by Earth's rotation, easterly, and westerly winds.
• Types of Cyclones:
  • Tropical Cyclones: Form over warm oceans, driven by heat and moisture.
  • Extratropical Cyclones: Develop in mid-latitude regions and are associated with cold and warm fronts.
• Conditions for Formation:
  • Ocean surface temperature 27°C.
  • High humidity and latent heat availability.
  • Weak vertical wind shear.
  • Pre-existing low-pressure zones and Coriolis force (>5° latitude).
  • Cyclones dissipate when they encounter cool waters, increased wind shear, or land, cutting off their moisture supply. Advanced monitoring systems and early warnings help mitigate their impact.