Weather News

How the East Coast Lows compare

Rob Sharpe, Saturday May 2, 2015 - 13:03 AEST

New South Wales and then Queensland have been smashed by seperate east coast lows in the past fortnight, producing deadly flooding rains.

Yesterday the east coast low affecting the eastern seaboard reached its peak in ferocity, causing major flooding before weakening as it spread rain down the NSW coast. But how does this system compare to the once in a generation east coast low that crippled the Hunter a week and a half ago?

Both systems developed with the interaction between warm, moist air in a low pressure trough along the east coast and the approach of an upper level trough over NSW. These two features cause widespread instability to develop in the atmosphere as well as causing rotation.

In terms of the heaviest rainfall, the two systems startlingly similar. Close to the centre of the low pressure system very severe thunderstorms developed, with very heavy rainfall. In Dungog and Maitland, as well as in Caboolture and Beerburrum, rainfall rates reached close to 100mm/hr, with totals near 300mm in under 24 hours. This rainfall caused major flooding in rivers and streams, sadly leading to the loss of life.

The NSW east coast low was worse than the current system because it also produced powerful winds for three days from the Hunter to the Illawarra. Winds reached gale force each day from Monday to Wednesday in the Hunter and Sydney. This combined with sodden ground helped trees and powerlines to come crashing down left, right and centre, particularly in the Hunter where gusts reached 135km/h. By comparison, in southeast QLD the east coast low only produced widespread rain for two days, with wind gusts peaking a touch over 100km/h on Moreton Island.

Thankfully this current system has not continued to spread its destruction down the NSW coast, as it is now weakening further like most east coast lows tend to do.

More good news comes in the form of the forecast for the next week or two. A series of cold fronts are likely to move across southern Australia, producing a westerly flow for NSW that will sometimes poke into QLD. This means that blue skies will become the norm as people work hard to clean up and create a sense of normality in the hardest hit communities on Australia's badly beaten east coast.

- Weatherzone

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