Tracking tropical cyclones to improve risk assessment
HR Wallingford scientists have developed a method to allow for much more precise modelling of likely future cyclone events.
Although cyclone seasons are well-known, being able to predict precisely where and how severely these storms are likely to affect a particular location is much harder to calculate. Cyclones are erratic weather phenomena, and the historical data available is often not sufficiently detailed to be able to base future predictions on. This is especially true in parts of the world where the record-keeping of tropical storms is relatively recent. But what if you could access information on thousands of years of cyclones? HR Wallingford scientists have developed a method to expand the dataset for specific sites, allowing for much more precise modelling of likely future cyclone events.
A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is fuelled by water with a temperature above 26.5°C. The characteristic and damaging features of tropical storms, are low atmospheric pressure with high winds and heavy rain, resulting in large waves and destructive surges at coasts.
Low pressure at the centre of the cyclone causes the sea level to bulge, and strong cyclone winds push the water ahead. Sites with a wide continental shelf experience a larger surge than those with a narrow shelf. Shallow water and constrictions such as estuaries and bays also enhance the wind-driven surge. But the effects can be very localised. Only specific cyclone tracks cause a significant surge, and calculating wind fields is crucial for accurate wave prediction.
Dr Stephen Grey, Principal Marine Scientist in the Coasts and Oceans Group at HR Wallingford, said: “Our aim was to find a way to improve the methodology for predicting the occurrence of severe tropical storms at a given location. Having identified sources of historical cyclone track data, we set out to develop tools to extract, analyse and quality control this data. We then investigated methods to simulate cyclone wind fields, and to investigate and validate the modelling of cyclone induced surge and waves.”
Cyclones were modelled using TELEMAC-2D and SWAN open-source software to predict surge and wave conditions at the site for each cyclone.