Awakening of Insects: Hawks become doves

September 22nd, 2011
by Jo Law

The Twentieth of September recorded the highest minimum temperature of 17.1ºC and the highest maxmium temperature of 25.8ºC (superceding the previous maximum recorded on 14th September) so far. The day also experienced the highest maximum wind gust of 76 km/h of the month from a South West direction recorded at 14.35.

A former colleague of mine once said, ‘In Perth, we have rain; in Sydney, they have weather.’ This comment heralded our arrival in the Illawara at the end of a very wet June in 2007. The comparatively dry July and August were followed by a rather squally September. As the howling winds swept through, the double garage doors would shake and bang violently until they burst open, jolting us from our sleep. Later I learnt that this spring wind is sometimes called ‘the August wind’. A highest wind speed recorded at the University of Wollongong AWS (now closed) is 148 km/h on 21st August 1981.

Wind is the movement of air resulting from the differences in pressure generated by the uneven heating of the Earth by the Sun. Global wind patterns including the trade winds, the westerlies and polar easteries originated from the powerful convection currents in the equatorial and tropical regions. The directional motion of the wind patterns is caused the rotation of the Earth (what is known as the Coriolis effect). The causes of seasonal winds are more varied. Commonly the outcome of weather systems brought about by changes in land and sea temperatures, the local topography, such as elevated landform and proximity to the oceans, also plays a big part.

The ‘August wind’ appears to be seasonal and its intensity enhanced by the specific landforms of the Illawarra. Researchers at the Centre for Australian Weather and Climate Research remarked on the severity of these seasonal wind gusts in a discussion and raised a number of possible factors  including mountains waves, katabatic (or downslope) winds, and hydraulic jumps. They did not reach a conclusion.

Meanwhile, the stong wind on 20th buckled the newly constructed WIN stadium in Wollongong, prompting The Illawarra Mercury to run a number of front-page articles and editorials demanding answers to how the grandstand roof of this $29 million construction rated for 150 km/h could be so critically damaged by gusts half that speed. Here in Austinmer, we are more concerned about whether we will be able to finish our box kite in time to catch the wind.

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