Showing posts with label cool change. Show all posts
Showing posts with label cool change. Show all posts

Friday, 4 November 2011

Melbourne's warm weather, Victoria's bushfires and the cool change

It's sometimes a surprise to people new to the city to learn that Melbourne is the hottest city in Australia...

...by one measurement anyway.  Sydneysiders and Brisbanites like to mock their southern cousins for living in a "chilly" city.  Melburnians certainly experience cooler winters, as befits people living as close to Antarctica as it's possible to get on the Australian mainland.  Anyone from Northern Europe or much of the USA or Canada may question the accuracy of the description, though.

But when it comes to the ability consistently to deliver the hottest day of the year, Melbourne trounces every other city in the country.  
Melbourne, 2009

The height of summer is in January and February.  If you look at the average temperature figures  for these months, you will see a pleasant range, between a low of about 14̊ centigrade and a high of around 26̊.  But for some days in every summer, winds will gather in the far north or northwest.  After sweeping their way across four thousand kilometres of roasting desert, picking up temperature on the way, they throw themselves onto Melbourne with all the force of a continent's heat, before rushing on to cool themselves over the Southern Ocean.

On days like this, Melbourne's temperatures will shoot up to 40̊ centigrade or more, and if you're very unlucky they won't drop below the mid 20s even at night.

Several of Australia's cities get up into the 40s at some point during summer, but Melbourne generally has the knack of topping them.  Perhaps the most extreme example came in 2009 when, between the 28th and 30th January, the city experienced three successive days in excess of 43̊ C, followed about a week later by its all time record of 46.4̊.

Melbourne's heatwave crown rests uneasily on her head.  Quite apart from the personal discomfort of her residents, the city sits in the state of Victoria, which is one of the most fire-prone places on earth.  Whether started by happenstance or (regrettably) arson, when a blaze gets going it can be virtually impossible to extinguish, particularly whilst it's being fanned by a strong, hot wind.  The 2009 temperatures helped cause the devastation of the Black Saturday bushfires in which, tragically, 173 people died and 414 were injured.  Property was devastated and many survivors were rendered homeless.  

During a major fire there's a good chance that the smoke from its incinerated hinterland will blow over the city, filling the air with a slight mist and invading your nose and throat, and making it impossible to forget what's unfolding perhaps just a hundred kilometres away.  Victoria's propensity to fire is truly astounding:  the coloured areas on this map show only the major areas that have been burnt out over just the last ten years.

When they're in the middle of one of these enervating heatwaves, one thought keeps Melburnians going:  the cool change.  This is what they call the weather fronts that bring relief from the oven-like temperatures.

If her summer temperatures are noteworthy, Melbourne's cool changes are quite impressive too.  Suddenly, the wind will swing from the north to the west or south, and the change is instantaneous.  The mercury may drop by fifteen degrees in as little as ten minutes, and people go from planning trips to the beach to putting on an extra layer of clothes.  I have yet to complain about this inconvenience.