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Context

Recently Cyclone Garance hit La Réunion Island causing extensive damage & fatalities underscoring La Réunion vulnerability to tropical cyclones & emphasizing need for improved disaster preparedness & response mechanisms.

Réunion Island

Geographical Location and Formation:

Réunion lies about 680 km east of Madagascar & 180 km southwest of Mauritius forming part of Mascarene Archipelago along with Mauritius & Rodrigues Islands.

Covering an area of 2,511 square kilometres it is small but geologically significant.

Volcanic Origins and Landscape:

It is entirely volcanic & formed on ocean floor at depth of 4,000 meters (13,000 feet). This active volcanic history has shaped the rugged terrain of the island making it a haven for geologists.

1. Piton de la Fournaise: One of world most active volcanoes
2. Piton des Neiges: highest point in the Indian Ocean standing at 3,070 meters above sea level. It is an extinct volcano

Climate and Biodiversity:

The island is also home to deep ravines & dramatic cliffs. These rugged mountains are dissected by torrential rivers which carve through land creating dramatic landscapes like cirques (natural amphitheaters formed by volcanic erosion).

Réunion has a tropical climate characterized by humid warm conditions year round with distinct wet & dry seasons.

The diverse ecosystems range from tropical rainforests in lower altitudes to alpine vegetation at higher elevations making it a UNESCO World Heritage Site for its rich biodiversity.

Major Cities and Settlements:

Capital of Réunion is Saint-Denis located on northern coast of island.

Other key towns include Saint-Pierre in south and Saint-Paul which is known for its scenic coastline and historical significance.

Historical Background:

Réunion was first settled in the 17th century by French colonists who initially used the island as a strategic outpost in the Indian Ocean.

French is official language and island is a region of France. Creole a French-based language with African, Malagasy & Indian influences is widely spoken alongside French.

Enslaved people from East Africa were brought to work on sugar plantations.

After abolition of slavery in 19th century indentured laborers from India (especially from Malabar and Bengal) as well as Chinese, Malays and Annamites (Vietnamese) were imported to replace enslaved workforce.

The majority of population today is of mixed descent with African, European &South Asian roots.

Economy and Agriculture:

Réunion economy is reliant on agricultural as well as industrial sectors. The island has long history of sugar production which remains cornerstone of its economy.

Sugarcane is primary crop & Réunion is known specialty items like geranium essence & vanilla.  The island also produces meat and milk products as well as tobacco. 

Culture and Music:

The island music is fusion of African rhythms, Indian beats & French influences.

Popular genres include maloya which has African roots & séga rhythmic dance music style that has origins in the island colonial period.

Cyclone Garance

Cyclone Garance was an intense tropical cyclone classified under Southwest Indian Ocean tropical cyclone scaleused by Météo-France (La Réunion).

Equivalent to: Category 3 hurricane on the Saffir-Simpson Scale, Very Severe Cyclonic Storm (VSCS) under IMD classification

Formation of Cyclone Garance:

Warm Ocean Waters

Western Indian Ocean had sea surface temperatures (SST) above 26.5°C providing necessary heat & moisture for convection.

Warm water acts as an energy source fueling rapid intensification of cyclones.

Low Wind Shear

Wind shear refers to change in wind speed & direction with altitude.

Low vertical wind shear allowed cyclone to develop a well defined structure without being disrupted.

Coriolis Effect

Earth rotation causes the Coriolis effect which helps cyclonic systems spin counterclockwise in Southern Hemisphere.

Since Garance formed away from the equator Coriolis force was strong enough to initiate rotation.

Pre-existing Disturbance

A tropical wave or disturbance provided initial convection.

Rising warm air created low-pressure center which intensified into depression before evolving into full fledged cyclone.

Why Did Cyclone Garance Intensify So Rapidly?

Favorable Upper Level Winds: Strong outflow at higher altitudes allowed cyclone to release heat in better way promoting further intensification.

Moisture Availability: High humidity levels in atmosphere supported continuous cloud development & rainfall.

Eyewall Replacement Cycle (ERC): If an intense cyclone undergoes ERC it can weaken temporarily but later regain strength. This process was observed in Garance.

Types of Cyclones  

Sources:

AL JAZEERA