DISTRIBUTION

Tropical cyclones and temperate cyclones (extratropical cyclones) are distinct weather systems that form under different conditions and have varying distributions globally and regionally.

1. Distribution of Tropical Cyclones

Characteristics:

Tropical cyclones are intense low-pressure systems that form over warm ocean waters near the equator. They are fueled by latent heat released from condensation within thunderstorms and have distinct seasonal and regional distributions.

a. Geographic Distribution:

  • Tropical Regions: Tropical cyclones primarily occur in the tropical regions of the world, between approximately 30°N and 30°S latitude, where sea surface temperatures are warm enough to sustain their development (typically above 26.5°C or 80°F).
  • Pacific and Atlantic Basins: Tropical cyclones are most common in the Pacific and Atlantic Ocean basins, where warm waters provide the energy needed for their formation and intensification.

b. Seasonal Distribution:

  • Seasonality: Tropical cyclones have distinct seasonal peaks influenced by regional climatic factors:
    • North Atlantic: Peak season is from June to November, with most storms occurring in August and September.
    • Northwestern Pacific: Peak season is from May to November, with most storms occurring in July and August.
    • North Indian Ocean: Two peak seasons: pre-monsoon (April to June) and post-monsoon (October to December).

c. Examples:

  • Atlantic Basin: Hurricanes such as Katrina (2005) and Irma (2017) are examples of intense tropical cyclones that affect the Caribbean Islands, the Gulf Coast of the United States, and Central America.
  • Pacific Basin: Typhoons like Haiyan (2013) in the Philippines and Japan are examples of powerful tropical cyclones impacting East Asia and the Pacific Islands.
  • Indian Ocean: Cyclones such as Cyclone Amphan (2020) and Cyclone Fani (2019) affect the eastern coast of India, Bangladesh, Myanmar, and neighboring countries.

2. Distribution of Temperate Cyclones (Extratropical Cyclones)

Characteristics:

Temperate cyclones, or extratropical cyclones, form outside the tropics in regions of strong horizontal temperature gradients. They are responsible for much of the weather variability in mid-latitudes and have distinct distribution patterns.

a. Geographic Distribution:

  • Mid-Latitudes: Extratropical cyclones occur primarily in the mid-latitudes (30° to 60° latitude) of both hemispheres, where cold polar air meets warmer air masses from lower latitudes.
  • Paths: Extratropical cyclones often move from west to east due to the prevailing westerly winds in these regions, influenced by the polar and subtropical jet streams.

b. Seasonal Distribution:

  • Year-round: Extratropical cyclones occur throughout the year but are more frequent and intense during the winter months when the temperature contrasts between air masses are strongest.

c. Examples:

  • European Windstorms: Extratropical cyclones frequently affect Western Europe during the winter months, bringing heavy rainfall, strong winds, and occasionally snowfall.
  • North America: Nor’easters are extratropical cyclones that affect the East Coast of North America, bringing heavy snowfall and strong winds, especially in winter.

3. Cyclones in India

Tropical Cyclones:

  • Bay of Bengal: Cyclones originating here affect the eastern coast of India and neighboring countries like Bangladesh and Myanmar. They typically occur during the pre-monsoon (April to June) and post-monsoon (October to December) periods.
  • Arabian Sea: Cyclones originating here affect the western coast of India and neighboring countries. They are less frequent but can occur during the pre-monsoon and post-monsoon periods.

Temperate Cyclones:

  • Impact: Extratropical cyclones affecting India usually arrive from the west, bringing winter rainfall and occasional thunderstorms to regions like northern India and the Himalayan foothills.

Conclusion

Tropical and temperate cyclones have distinct distributions based on their formation mechanisms, seasonal variability, and regional climatic factors. Understanding these distribution patterns is essential for meteorologists to forecast these storms accurately and for communities to prepare and respond to their potential impacts, including heavy rainfall, strong winds, storm surges, and flooding.

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