What is a cyclone?
A cyclone is a low-pressure area on the earth’s surface which generates revolving storms. Cyclones are characterised by a low-pressure zone forming over a warm ocean surface, which generates evaporation by heat convection. Large amounts of evaporating moisture act as the fuel of the low-pressure system, which draws in strong winds across the ocean surface. These typically warm, moist winds deliver more moisture and evaporative energy in the form of tropical thunderstorms. If the circumstances are right, the thunderstorms can begin to revolve around one another, leading to the development of a tropical cyclone.
One way to conceptualise how a low-pressure area turns into a cyclone is to imagine removing the plug from a bathtub. A low-pressure zone has been created over the plughole, and water rushes in from all sides. That water begins to spiral as it moves vertically.
Cyclones move erratically across the earth’s surface, seeking the path of least resistance. As a general rule, cyclones tend to move from East to West, and away from the equator although they can ‘turn-back’ on their path and shift course 180 degrees. However, cyclone forecasting is still not very well understood, and path predictions are unable to reliably forecast.
How do cyclones form?
Cyclones need a range of factors to be present in order to form. The most notable requirements are a sea surface temperature above 26.5C, a warm and moist troposphere (high temperature and humidity) and sufficient Coriolis force (which is only found more than 5 degrees/300 miles either side of the equator).
The fuel of a cyclone is the heat below (usually from a warm ocean surface). Once the heat and moisture is removed, the cyclone will dissipate. This is why cyclones cannot sustain themselves over land for more than a day or two.
In Australia, cyclones are rated by wind gust speed. There are 5 categories of cyclones, with 1 being the least damaging to 5 causing significant damage, both on land and at sea. Cyclone strength is measured by how low the pressure is below standard (1013hPa), the lower the central pressure of the storm the stronger the winds.
What have been the most notable cyclone events in Australia?
Cyclone Tracy (1975) was a historically significant cyclone, not only for its severity but also because it arrived on Christmas morning, leaving catastrophic destruction to Darwin and changing Australia’s attitude to cyclones forever.
Two other major, more recent cyclones, were Cyclone Larry in 2006, and Cyclone Yasi in 2011. Both these cyclones hit northern Queensland. Larry wiped out 80% of Australia’s banana crops and destroyed millions of dollars worth of avocadoes. Prices soared and stocks dwindled causing major shortages throughout the country. When cyclone Yasi hit, it was declared the most powerful storm the region had seen for decades. Originally on a direct course for Cairns, it crossed over land just outside of Cairns, near Mission Beach inflicting a direct hit on the marina at Hinchinbrook resulting in marine claims in the tens of millions of dollars. The total damage bill for Yasi was estimated as $800m-$1.5b by the Queensland Treasury.
When does the cyclone season begin in Australia?
In Australia, cyclone season generally begins around late October/early November and runs until late April/early May. On average, 11 cyclones form in the Australian region each year however only 3 or 4 will make landfall.
A strong La Niňa weather pattern exists this year. With the La Niña comes an increased risk of tropical cyclones due to warmer waters near the north eastern coast of Australia. For 2020-2021, the outlook suggests there is a higher chance of more cyclones than average for the Australian regions this season — and they are expected to form earlier than normal.
Cyclones typically affect Australian coastal regions north of the Tropic of Capricorn. This includes areas where there are many ports which handle export cargo and are home to significant numbers of vessels and marine infrastructure including Hay Point, Gladstone, Cairns, Gove, Darwin, Port Hedland, Port Walcott, Dampier and Barrow Island.
What can we learn and how can we prepare for Cyclone events in order to minimise risk?
While history is a great teacher, unfortunately predicting these weather phenomena is incredibly challenging. Cyclone forecasting is still not very well understood, and path predictions are unable to accurately forecast. The relationship of the La Niňa events and cyclones is however beginning to be understood.
“We have known for over 30 years that El Niňo – Southern Oscillation, of which the La Niňa is one extreme phase, affects the number of tropical cyclones in the Australian region, and that this allows us to predict, months in advance, whether a tropical cyclone season is likely to be active or inactive.” Professor Neville Nichols, Monash University.
As 2020/21 is a La Niňa year we are anticipating an active cyclone season. The unpredictability of the weather in Australia creates challenges for companies engaged in the shipping industry and those who transport or rely on the transport of cargo.
It is important for your clients to select the right insurance policy for them, especially for those operating in the northern parts of Australia. As we approach the cyclone season, now is the time to check-in with your clients and ensure they are prepared with the right cover.
At AM&T, our underwriters and our claims team understand the complex world of marine and transit insurance. Our team specialise in cargo, carriers, commercial hull and marine liabilities. Get the right cover for your clients by talking to the right team.
DisclaimerThis article has been prepared by AM&T (Allianz Marine & Transport) ABN 98 155 554 279 AR No. 423910) agent for the insurer Allianz Australia Limited ABN 15 000 122 850 AFSL 234708 (Allianz). Information contained in this article is accurate as at 05/11/2020 and may be subject to change. In some cases, information has been provided to us by third parties and while that information is believed to be accurate and reliable, its accuracy is not guaranteed in any way. Any opinions expressed constitute our views at the time of issue and are subject to change. Neither Allianz, nor its employees or directors give any warranty of accuracy or accept responsibility for any loss or liability incurred by you in respect of any error, omission or misrepresentation in this article. Acknowledgements Australian Bureau of Meteorology, Commonwealth of Australia.Conversations with Deputy Harbourmaster (Port of Dampier) Captain Heathcliff Pimento, Harbourmaster and Deputy Harbourmaster (Port Hedland) Captain Vikas Bangia and Captain Anurodh Prasad, 24 July 2020 and 24 August 2020.