We all know Australia's two largest cities are different. But on Wednesday, Sydney and Melbourne have been worlds apart in terms of weather.
Just before 3pm Wednesday afternoon, Sydney's official measuring station at Observatory Hill, beside the Harbour Bridge, was basking in temperatures of 33 degrees. Melbourne? A brisk 11. Let's put that in perspective:
- The temperature in Sydney just before 3pm was 7 degrees hotter than the average daily maximum for January, the city's hottest month;
- The temperature in Melbourne was 2 degrees colder than the average daily maximum for July, the city's coldest month.
This is what the Bureau of Meteorology's home page looked like for much of Wednesday afternoon.
Some other statistics of note:
- Sydney Airport reached 34.7 degrees on Wednesday;
- 34 was also recorded in Penrith, which as we wrote last summer, has a very good case for being considered Australia's hottest suburb;
- The hottest ever September temp of 34.6 at Observatory Hill appears to be safe for now, but it's a close thing.
The heat in Sydney is accompanied by total fire bans -- which you normally only see much closer to summer. Indeed homes are already threatened by fires in areas north of Sydney.
In addition to Wednesday's heat and blustery winds, Australia's most populous city and much of the east coast has endured an incredibly dry spell. Lush Sydney is a barren old town right now. Spring growth? Forget it. Spring wilting, more like.
There has been not a drop of rain in the 13 days of September to date. The last 40 days have seen just 1.4mm, which is barely enough to wet the lawn.
The dryness in Sydney is a symptom of consistent westerly winds which have blown for much of July, August and September to date.
Westerlies typically bring consistent showers from the southern Ocean to Melbourne -- and this has happened, with measurable rain on 28 of the 44 days in August and September. Westerlies also tend to be good news for snow lovers, and there are indeed some spectacular snow depths in NSW and Victoria this year.
But for Sydney, the westerly winds bring dry air. Once the air has crossed Victoria and the Great Dividing Range, there's little left in the way of moisture for the east coast. And the air is much warmer, as illustrated by this live reading from the Bureau of Meteorology's MetEye at 11:30 on Wednesday.
The weather map also helps explain things. Wednesday's hot outbreak is all about a north-westerly stream of air. Air moves anti-clockwise around a high pressure system. So if you look at the map below, air is streaming down towards Sydney from central Australia.
Meanwhile a very strong cold front is reaching Melbourne, which is why it's so cold there. That front will push into NSW on Thursday, bringing snow to the Alps and to low levels in areas close to Sydney like the Blue Mountains and Central Tablelands.
Sydney will likely reach just 18 degrees on Thursday and if you're willing to drive an hour or so out of town, you'll likely be able to throw a snowball. While it will be cooler in the harbour city, there's no chance of any significant rainfall for at least a week in either Sydney or other parts of NSW which are desperate for a soaking.
As summer approaches, what is for now a meteorological anomaly may escalate into an extremely serious situation unless substantial rain falls soon.