Cyclones

📚 Key Concepts

🔹 What is a Cyclone?

A cyclone is a large-scale rotating storm system with very low pressure at the center and high-speed winds spiraling around it.

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Characteristics:

  • Eye: Calm center with lowest pressure
  • Eye wall: Ring of strongest winds around the eye
  • Spiral bands: Outer regions with rain and moderate winds
  • Rotation: Counterclockwise in Northern Hemisphere, clockwise in Southern Hemisphere

🔹 Cyclone Formation

Requirements:

  1. Warm ocean water (temperature > 26°C)
  2. Low wind shear (uniform wind speeds at different altitudes)
  3. Sufficient distance from equator (for Coriolis effect)
  4. High humidity in lower atmosphere
  5. Atmospheric instability

Formation Process:

  1. Ocean heating creates warm, moist air that rises
  2. Condensation releases latent heat, warming air further
  3. More air rises, creating very low pressure area
  4. Surrounding air rushes in and starts rotating due to Earth’s rotation
  5. System intensifies as more energy is drawn from warm ocean
  6. Organized circulation develops with distinct eye and spiral structure

🔹 Cyclone Structure

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The Eye:

  • Diameter: 20-40 km typically
  • Calm conditions: Light winds, clear skies
  • Lowest pressure: Can drop below 900 mb
  • Warmest temperatures in the storm

The Eye Wall:

  • Most dangerous part of cyclone
  • Strongest winds: Can exceed 250 km/h
  • Heaviest rainfall
  • Towering clouds reaching 15-18 km height

Spiral Rain Bands:

  • Outer regions of cyclone
  • Moderate to heavy rain
  • Gusty winds
  • Tornado formation possible

🔹 Cyclone Classification

Based on Wind Speed:

  • Tropical Depression: < 63 km/h
  • Tropical Storm: 63-118 km/h
  • Category 1: 119-153 km/h
  • Category 2: 154-177 km/h
  • Category 3: 178-208 km/h
  • Category 4: 209-251 km/h
  • Category 5: > 252 km/h

🔹 Cyclone Effects

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Destructive Impacts:

  1. High-speed winds: Structural damage, uprooted trees
  2. Storm surge: Wall of water pushed ashore (3-12 meters high)
  3. Heavy rainfall: Flooding, landslides
  4. Coastal erosion: Permanent changes to coastline
  5. Agricultural damage: Crop destruction, soil salination
  6. Infrastructure damage: Roads, bridges, power lines
  7. Economic losses: Property damage, business disruption

Storm Surge:

  • Most deadly aspect of cyclones
  • Created by wind pushing ocean water toward shore
  • Height depends on: Wind speed, ocean depth, coastline shape
  • Can penetrate inland for several kilometers

🔹 Cyclone Prediction and Tracking

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Modern Technology:

  • Weather satellites: Monitor cloud patterns and temperatures
  • Radar systems: Track cyclone movement and intensity
  • Weather buoys: Measure ocean conditions
  • Computer models: Predict path and intensity changes
  • Aircraft reconnaissance: Direct measurement in cyclone

India Meteorological Department (IMD):

  • 24/7 monitoring of cyclone development
  • Early warning systems for coastal areas
  • Evacuation planning coordination
  • International cooperation for tracking

🔹 Cyclone Safety Measures

Before Cyclone:

  • Emergency kit: Food, water, medicines, flashlights, battery radio
  • Secure property: Board windows, secure loose objects
  • Evacuation planning: Know evacuation routes and shelters
  • Stay informed: Monitor weather reports regularly

During Cyclone:

  • Stay indoors in strongest part of building
  • Away from windows and glass doors
  • Avoid flooded areas
  • Never go outside during eye passage
  • Emergency communication only

After Cyclone:

  • Check for injuries and provide first aid
  • Avoid downed power lines
  • Drink only bottled/boiled water
  • Be cautious of damaged structures
  • Help community recovery efforts