Major Heat: Great rains sweep through

February 3rd, 2012
by Jo Law

In this last pentad of Summer, great rains indeed swept through with 73mm recorded at Bellambi (AWS). The Bureau of Meteorology tells us that ‘a low pressure trough lies over inland New South Wales, while a ridge extends across the southern Tasman Sea. This pattern, assisted by an upper-level system in the area, is generating rainfall across many central and eastern districts.’ The seasonal rainfall outlook issued by the Bureau previously predicting a wetter than average summer has come to pass although ABC Rurual News reports that while parts of Queensland and northern New South Wales are flooding, southern New South Wales are ‘in grip of drought’.

Australia is the second driest continent after Antartica. With the majority of the landmass located around 30º S latitude where high pressure systems dominate, more than 50% of the land recieves very low rainfall. On average 80% of Australia receives less than 300mm of annual rainfall, while the tropical and subtropical regions in the north can receive daily rainfall over 100mm with the highest annual rainfall of 12,461mm recorded in Bellenden Ker, Queensland in 2000. In addition to this variablity, the Southern Oscillation of El Niño and La Niña alternately bring less than average rainfall often resulting in drought and more than average rainfall resulting in flooding.

The current La Niña episode has brought the national water storage capacity to 78.8% compared to 71% this time last year and around 50% in 2010. Locally, the total monthly rainfall in January 2012 recorded at Bellambi (AWS) is 121.4mm compared to the mean rainfall of just 61.4mm. Climate statistics show Feburary to be the wettest and hottest month in the Illawarra and the Bureau of Meteorology forecasts a 45% chance of southeastern Australia exceeding than median rainfall in the coming 3 months. So great rains may yet again sweep through.

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