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Cyclones are powerful, rotating storms that form over warm tropical and subtropical oceans and generally move from East to West before turning towards higher latitudes. These cyclones are known as Hurricanes in the Atlantic and Northeast Pacific basins, and as Typhoons in the Northwest Pacific basin. Cyclones pose a significant threat upon landfall, causing heavy rain, strong winds, flooding, and widespread damage, which can degrade water quality, spread disease, and destroy infrastructure. In addition to the immediate physical destruction, the aftermath often leads to long-term challenges, such as disruption of essential services, economic loss, and environmental degradation. To mitigate these impacts and support recovery, building broad resilience is essential.

This page presents observed Tropical Cyclones from the International Best Track Archive for Climate Stewardship (IBTrACS) but primarily relies on simulated Tropical Cyclones generated by the Columbia HAZard Model (CHAZ, Lee et al. 2018) for most of the analysis. In most tropical places the occurrence of Tropical Cyclones in any one place is still rare, therefore the historical record is generally too short to allow for a robust estimation of recurrence intervals of these storms. Such historical uncertainty can be reduced somewhat using models, where large ensembles of Tropical Cyclones can be generated. The CHAZ Model simulates tropical cyclones across the oceans and their impact on landfall by generating an extensive synthetic catalog of possible cyclone tracks, offering a more comprehensive view than what can be obtained from observational data alone.​ The results presented here are currently based solely on the CHAZ Model, albeit driven by a broad array of 12 different Global Circulation Models (from the CMIP6 ensemble). CCKP is offering these products as first examples that are designed to assist users in engaging with Tropical Cyclone data, forming a better understanding of their statistical properties today, and then working in a scenario context to consider possible changes in the future. 

CCKP is grateful for the expertise and guidance of the Columbia HAZard Model (CHAZ) Team at Columbia University. 

We classify Tropical Cyclones using the Saffir-Simpson Hurricane Scale, which uses maximum sustained wind speed.

• Tropical Storm: 34 to <64 knots (63 to <118.5 km/h)​
• Category 1: 64 to <83 knots (118.5 to <154 km/h) ​
• Category 2: 83 to <96 knots (154 to <178 km/h)​
• Category 3: 96 to <113 knots (178 to <209 km/h)​
• Category 4: 113 to <137 knots (209 to <254 km/h)​
• Category 5: >= 137 knots (>=254km/h)

Below, cyclone information is presented as storm tracks and probabilities (number of storms per year), along with aggregated data at the global average, per ocean basin, per Exclusive Economic Zone (EEZ), and by landfall for associated territories or countries.

Cyclones are fueled by the release of energy from condensation of moisture that has evaporated from the warm ocean surface. If the conduit of moisture can be sustained, which generally happens if the sea surface temperatures are above 26 or 27 degrees Celsius, the storm clusters grow, the central pressure drops, and the convection can become self-sustaining. The Coriolis effect tends to impose rotation on the evolving systems and eventually a Tropical Cyclone system can form that is increasingly taking on a concentric shape as it grows.  

In the Northern Hemisphere, cyclones initially move westward and then curve northward where they get into contact with the prevailing westerly flow where they either dissipate due to windshear or where they turn into extratropical cyclones on the way eastward. Equally, in the Southern Hemisphere, they move westward before curving south and eventually southeastward. Cyclones cannot form around the equator (between approximately 4°S and 4°N) because the Coriolis effect is too weak there to maintain their rotation and thus the self-sustaining dynamic is not achieved. Cyclones are very rare in the South Atlantic and on the western coast of South America primarily because of the cold waters there.

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