Frequently Asked Questions (FAQ)

Climatology | Impacts | Extremes| TCs affecting WA towns | Forecast Accuracy
Frequently Asked Questions | Annual summaries

Definitions | Characteristics and Formation | Climatology | Extremes | Forecasting | More Information

Definitions

2. What is the tropical cyclones intensity scale? How is this different from the USA intensity scale?

The severity of a tropical cyclone is described in terms of categories ranging from 1 (weakest) to 5 (strongest) related to the zone of maximum wind gusts as shown in this table.
Note: corresponding sustained winds and central pressure are also provided as a guide.

The USA utilizes the Saffir-Simpson hurricane intensity scale for the Atlantic and Northeast Pacific basins. Go to the US Atlantic Oceanographic and Meteorological Laboratory's Hurricane FAQ page for more information about this scale.

The table below provides a comparison of the USA hurricane scale with the Bureau of Meteorology's 5-point tropical cyclone categories. A complicating factor is that the wind averaging period used in the USA is one minute whereas it is ten minutes in the Australian region. One-minute winds have been converted to ten minute winds using a conversion factor of 0.88. The associated wind gusts are also listed, the conversion factor from the ten minute winds being 1.41. The demarcation points are not precise - this table is intended to provide a rough comparison only.