Cyclones
A cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure, known as a cyclone's eye. Cyclones form over warm ocean waters near the equator where the sea surface temperature exceeds 26.5°C (79.7°F) to a depth of at least 50 meters. Here are some key aspects:
Types of Cyclones
- Tropical Cyclones - These are known by different names in various parts of the world: Hurricanes in the Atlantic and Northeast Pacific, Typhoons in the Northwest Pacific, and Tropical Cyclones or Cyclones in the South Pacific and Indian Ocean.
- Extratropical Cyclones - These occur outside the tropics and are typically associated with weather fronts, often leading to widespread rain or snow, and can be much larger in scale.
- Subtropical Cyclones - A hybrid of tropical and extratropical cyclones, they have characteristics of both.
Formation and Structure
The formation of a cyclone involves several stages:
- Tropical Disturbance - A cluster of thunderstorms with no clear circulation.
- Tropical Depression - When circulation becomes more organized and winds reach speeds up to 38 mph (62 km/h).
- Tropical Storm - Winds reach speeds between 39-73 mph (63-118 km/h).
- Hurricane/Typhoon/Cyclone - Winds exceed 74 mph (119 km/h).
The structure includes:
- The eye - A relatively calm, clear center where sinking air inhibits cloud formation.
- The eyewall - A ring of towering thunderstorms where the most severe weather occurs.
- Rainbands - Spiral bands of clouds and thunderstorms that extend outward from the eyewall.
Impact and Effects
- Storm Surge - The rise of water associated with the low pressure and strong winds of a cyclone.
- Wind Damage - High winds can cause significant structural damage.
- Flooding - Heavy rainfall can lead to inland flooding.
- Tornadoes - Cyclones can spawn tornadoes.
- Economic Impact - Damage to infrastructure, agriculture, and loss of life can have long-term economic repercussions.
Historical Perspective
Historically, cyclones have had profound impacts:
- In 1970, the Bhola cyclone in East Pakistan (now Bangladesh) resulted in an estimated 300,000 to 500,000 deaths, making it one of the deadliest tropical cyclones on record.
- The Great Hurricane of 1780 in the Caribbean is noted for causing the highest number of deaths in a single Atlantic hurricane with around 22,000 fatalities.
Current Research and Prediction
Modern technology and research have improved cyclone prediction:
- Satellite Imagery, Radar, and Buoys provide data for tracking and forecasting.
- Computer models simulate cyclone behavior for better prediction.
- Research into cyclone genesis, intensity, and track has led to more accurate forecasts.
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