Stormy weather is coming: A word on tropical cyclones from our severe weather expert

Stormy weather is coming: A word on tropical cyclones from our severe weather expert

Author: Bruce Buckley, Principal Climate Research Analyst, Insurance Australia Group
The release of the Australian Bureau of Meteorology’s tropical cyclone outlook reminds us that the tropical cyclone season for Australia is now upon us. The Bureau’s outlook is found here:

Although it is a strong El Niño season and the total number of tropical cyclones may be reduced compared to normal years there have been very intense tropical cyclone impacts in previous El Niño years. You only have to go back to the 2009/2010 El Niño and recall that there were four tropical cyclone impacts on the coast that season, including TC Ului that significantly damaged the Whitsunday region of Queensland.

Did you know? Tropical cyclones are also known as typhoons in the east Asian region and hurricanes in the American region

Tropical cyclones, which are called typhoons in the east Asian region and hurricanes in the American region once they are severe, are sometimes confused with tornadoes. Tornadoes are very localised funnel clouds attached to severe thunderstorms while tropical cyclones are much larger, longer-lived weather systems that have to have well developed circulation with wind speeds of gale force or greater (63km/h average wind speeds with gusts 90km/h or more) affecting large areas.

In Australia the intensity of tropical cyclones is simplified into five categories, as shown in the Table following. This intensity scale is different to the scale used to describe tropical cyclones (hurricanes) in the USA region, which is the Saffir Simpson Hurricane Intensity Scale. Once a tropical cyclone reaches Category 3 intensity it is classified as a severe tropical cyclone. However, even low category tropical cyclones can be very damaging, such as category 1 TC Wanda that triggered the devastating Brisbane floods in 1974.
Category Maximum Mean Wind (km/h) Typical Strongest Gust (km/h) Central Pressure (hPa) Typical Effects
1 63 - 88 < 125 > 985 Negligible house damage. Damage to some crops, trees and caravans. Craft may drag moorings
2 89 - 117 125 - 164 985 - 970 Minor house damage. Significant damage to signs, trees and caravans. Heavy damage to some crops. Risk of power failure. Small craft may break moorings.
3 118 - 159 165 - 224 970 - 955 Some roof and structural damage. Some caravans destroyed. Power failures likely. (e.g. Winifred)
4 160 - 199 225 - 279 955 - 930 Significant roofing loss and structural damage. Many caravans destroyed and blown away. Dangerous airborne debris. Widespread power failures. (e.g. TracyOlivia)
5 > 200 > 279 < 930 Extremely dangerous with widespread destruction. (e.g.Vance)

Table 1: The Australian Tropical Cyclone Intensity Scale. Source: The Australian Bureau of Meteorology.

Did you know? In Australia once a tropical cyclone has sustained gale force winds it is given a name, if it leads to death or major property damage its name is then retired.

In Australia once a tropical cyclone has sustained gale force winds it is given a name (from an assigned list), with alternating male and female names that run through the alphabet. Any tropical cyclone that leads to a death or major property damage has its name retired. To view the list of names visit -

The cost of tropical cyclone impacts

The Insurance Council of Australia published the top 10 most damaging catastrophe events for Australia through to the end of 2011. Tropical cyclones made up three of these with Tropical Cyclone Tracy, which destroyed Darwin on Christmas eve in 1974, the second most damaging natural disaster for Australia. Its damage bill, in 2011 dollars, is estimated to be over $4,000 million. Other cyclones in the top 10 are TC Madge (1973) and the more recent TC Yasi that struck the Innisfail region in 2011.

Did you know? 3 of the 10 most damaging Australian catastrophe events up until the end of 2011 were tropical cyclones.

The most recent Tropical Cyclone to significantly damage Australian property was TC Marcia that struck the Yeppoon – Rockhampton region in February this year.

Marcia, which produced insured damage totalling $522 million according to Insurance Council of Australia figures, served as a reminder that even parts of Australia that have not experienced a tropical cyclone in recent years, even recent decades, are still vulnerable to tropical cyclone impacts. You only have to look at the Bureau of Meteorology’s tropical cyclone track map spanning the period from the 1908/1909 season through to the 2006/2007 season to see that a very large portion of the Australian coastline and inland areas are susceptible to cyclone related damage.

Protecting your company and personal property

Damage from tropical cyclones can come in several guises and can be extremely severe. There can be direct damage produced by destructive winds that accompany the passage of a tropical cyclone, or flash and river flooding from the cyclone’s very heavy rainfall, a combination of wind and rain damage, or storm surge from elevated sea levels. There can be prolonged power and telecommunication outages. Water supplies can be interrupted, as can all forms of transportation.

Business interruption following a major tropical cyclone impact can therefore be substantial.

CGU have a wide range of insurance options to cater for the needs of every business that operates in tropical Australia. CGU have been providing insurance in tropical Australia for over 160 years and so have a very good understanding of the types of damage and disruption tropical cyclones can bring.

Damage claims are rapidly assessed and a wide range of specialist repairers are on CGU’s books to ensure any damage is rectified as quickly as possible.

CGU also offer a range of marine insurance should you have a boat, yacht or other marine vessel that needs protection.

Visit the Australian Bureau of Meteorology’s  website here -

Images (L-R): Image 1: A pile-up of boats in Hinchinbrook Marina following cyclone Yasi. Source: Picture: Paul Crock/AFP Image 2: Satellite image of Marcia right at the time of landfall  Source: US Naval Research Laboratory / Japanese Meteorological Agency / NOAA Image 3: A home in Yeppoon suffered heavy damage as Marcia swept through. Source: Picture: Peter Wallis

About the Author

Bruce Buckley has been Principal Climate Research Analyst with Insurance Australia Group for over 7 years. Bruce has also been team meteorologist for the Australian Sailing Team for the London and now Rio Olympic Games.

Prior to joining the IAG team, Bruce spent 30 years at the Bureau of Meteorology in the Perth, Melbourne and Sydney Offices in various senior roles, including spending more than 10 years at the Perth Tropical Cyclone Warning Centre. Bruce is co-author of 5 books and author of around 20 scientific publications.