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Environment

Jan 16, 2014

Hot enough for you? A meteorological explanation of the heatwave

Bit hot, huh? So what's going on with the weather patterns? Crikey asked our favourite meteorologist, Channel Ten presenter Magdalena Roze, to explain. You better get used to it.

hot

It’s too darn hot — and it’s going to get hotter. Get ready for the mercury to notch up a couple more degrees, with today on track to be the hottest day of the heatwave. Many towns and cities are set to break all-time records in what is now day four or five of sweltering conditions.

We are sweating through Australia’s second major heatwave for 2014 (and we’re just two weeks in). And it comes after the nation’s hottest year in over 100 years on records.

So why is it so bloody hot? From a weather perspective, it’s a pretty stock-standard scenario. From a climate perspective, it is anything but stock standard. The concern (and reality) is that this — longer, hotter, more frequent heatwaves — are becoming stock standard. It is no longer a prediction. We are living in a changing, warming climate.

Weather-wise, one of the main culprits of the heatwave is a “blocking high” in the Tasman Sea that is churning hot northerly winds over south-east Australia. Normally, a high moves on after a couple of days, allowing cooler systems from the south carrying cold air to replace the heat and provide some relief. But this high isn’t moving on — not only is it deflecting cool changes, it is also the mechanism that is carrying hot air towards the south-east, day in day out.

Fortunately, it is moving  away later Friday, so after two more days of record-breaking heat, Adelaide is forecast to get a cool change late Friday afternoon and Melbourne late Friday evening.

Blocking highs are usually a primary cause of heatwaves. But what is extraordinary about this heatwave (and more recent ones) is how hot the heat source is and the fact that there isn’t a phenomena such as El Nino “pushing” the weather towards hotter conditions.

This record-breaking heat is occurring in “neutral” El Nino conditions. A quick refresh: during a strong El Nino we typically see our worst droughts/heatwaves in south-east Australia, and during a strong La Nina we typically see above-average rainfall and cooler temperatures over eastern Australia. So breaking heat records for duration and intensity in these current neutral El Nino conditions is like a race car driver recording his fastest speed in rain with poor tyres.

So what’s to come?

The frequency, duration and intensity of both heatwaves and hot days have increased in the last 30-40 years, and record hot days are outweighing record cold days by three to one. Australia’s longer, hotter and more frequent heatwaves are consistent with climate change predictions — and the trend is expected to continue. Of course, there will still be cold days and cold spells — that is just the weather — but the overall climate trend is one of warming.

*Magdalena Roze presents weather on Channel Ten news bulletins and tweets at @magdalena_roze

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32 comments

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32 thoughts on “Hot enough for you? A meteorological explanation of the heatwave

  1. MJPC

    MR,so the frequency, duration and intensity of heatwaves has increased and this is consistent with climate change predictions so, then why do we have climate skeptics running this country ably supported by the gutter , and not so gutter, press such as recent SMH artcles by Tom Switzer.
    Thank you for an experts viewpoint, not just some LNP flunky pushing the carbon energy industry barrow.

  2. K.D. Afford

    Sad isn’t it when we had such a vicious attack dog as opposition leader in Abbott who has gathered business druggies and pay members like Hunt who even denies the evidence of his own education, that the penny has not dropped for these self serving people. Abbott will be doing a lot of coughing into his hand if he ever allows the media to ask him why he is acting against the interest of humanity in not being a leader to tackle climate change.

  3. paddy

    Nice clear explanation MR. Thanks

  4. Stuart Coyle

    I thought the government was taking “direct action” to stop this sort of thing happening? Maybe we are not being told what they are doing because of “operational” reasons. It certainly could not be the case that they are doing nothing, could it?

  5. Mark Duffett

    In addition to El Niño/ENSO, Roze could also have mentioned the related Pacific Decadal Oscillation. That we are presently in a cool phase of the PDO has been recently identified as the main reason why global warming has slowed since 1998 (covered in the latest Nature, out today nature.com/news/climate-change-the-case-of-the-missing-heat-1.14525). It turns out the negative phase of the PDO that commenced in 1998 is the likely reason why increased heat has been going into the ocean instead of the atmosphere, accentuating the rain/bald tyres of Roze’s metaphor.

    The PDO reverses with a period of 15-30 years, i.e. it could do so at any time from now on. When it does, we will get more and stronger El Niños, and Australian temperature rise will increase rapidly.

  6. Honest Johnny

    Conservatives such as Abbott, Cardinal Pell, Tom Switzer, Rupert Murdoch et al will never, even in the face of glaring evidence, never admit that climate change has been brought about by human activity. Why? Because it plays into the hands of their political enemies, the progressives, and especially gives Greenies oxygen. Admitting that human based industrialisation caused this is a basic contraposition to conservative thinking.

  7. CML

    If anyone thinks there is no global warming, they should try living here in Adelaide as we have all done this week. It is very hot and very uncomfortable. There has been a big increase in heat related health issues, especially for the elderly.
    To do nothing about the cause of these extreme temperatures is criminally negligent. I hope Abbott and his motley crew are proud of the increased suffering they are ignoring.
    Guess that’s okay, so long as their mates can continue to make squillions!

  8. Charlie Maigne

    Extreme heatwave? “Oh, we’ve had hot days in the past, and we’ll have them again.”

    Extreme cold snap? “Where’s your global warming now?”

    Extreme bushfires? “YOU’RE POLITICISING TRAGEDY!”

  9. Jimmyhaz

    What I really hate is those that say that the scientists are in it for the money. If they actually were, they’d be spouting whatever popped into the oil companies minds, as there’s orders of magnitude more to be made in non-renewables than there is in scientific grants.

  10. AR

    It won’t be long before TT & his Uglies declare a “war on science” – that way there will be no need for pressers or information as it would aid … errr.. the aahh.. atmospheric enemy.
    Cue Robbie Z – “Ya don’t need a Weatherman to know which way the wind blows”.

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