Tropical Cyclone Scales - South-Western Indian Ocean

South-Western Indian Ocean

Any tropical cyclone that forms within the Southern Indian Ocean to the west of 90°E is monitored by Météo-France who run the Regional Specialized Meteorological Center in La Reunion. RSMC La Reunion uses seven different categories to measure the wind speed of a tropical cyclone. It is based on a 10-minute average maximum sustained winds, rather than 1-minute maximum sustained winds, which is what the Saffir-Simpson Hurricane Scale uses.

A tropical disturbance is the lowest category on the South-west Indian Ocean Tropical Cyclone scale, and has wind speeds of 28 knots (50 km/h, 32 mph). A tropical disturbance is designated as a tropical depression when the disturbance reaches wind speeds above 28 knots (32 mph, 50 km/h). Should a tropical depression reach wind speeds of 35 knots (65 km/h, 40 mph) then it will be classified as a moderate tropical storm and assigned a name by either the Sub Regional Center in Mauritius or Madagascar.

Should the named storm intensify further and reach winds speeds of 48 knots (89 km/h, 55 mph), then it will be classified as a severe tropical storm. A severe tropical storm is designated as a tropical cyclone when it reaches wind speeds of 64 knots (118 km/h, 74 mph). Should a tropical cyclone intensify further and reach wind speeds of 90 knots (166 km/h, 103 mph), it will be classified as an intense tropical cyclone. A very intense tropical cyclone is the highest category on the South-West Indian Ocean Tropical Cyclone scale, and has winds of over 115 knots (212 km/h, 132 mph).