Here’s how a complex low-pressure system sent temperatures plummeting



File 20180510 5968 1dba37n.png?ixlib=rb 1.1
The complex low weather system currently swirling over south-eastern Australia.
Bureau of Meteorology

Adam Morgan, Australian Bureau of Meteorology

New South Wales, Victoria, Tasmania and South Australia are currently affected by a massive complex low pressure system, dropping temperatures and bringing rain, hail, wind and snow.

While complex low pressure systems like this come along every year or so, some Australians may be feeling whiplash after a particularly warm autumn.

Complex lows

Typically, as Victoria and Tasmania head into winter we see cold fronts that move from west to east, generating rain and thunderstorms. This weather system started off like that, but developed into a complex low that will stay with us for the rest of the week.

It’s the kind of weather system you see on average once every year or two. What is a little unusual is to see such a deep pool of cold Antarctic air so early in May. Canberra, for example, is forecast to have a maximum of 9℃ on Friday – which would be its coldest day in the first half of May since 1970.




Read more:
Cold weather is a bigger killer than extreme heat – here’s why


In weather-speak, “complex” describes a weather system with an intricate structure. Starting as a cold front across Victoria and Tasmania, this complex low now has multiple low-pressure centres at the surface, and is interacting with a broad low-pressure system in the upper levels of the atmosphere. These upper and low-level weather systems reinforce each other.

The other factor contributing to the complexity is the warmer waters of the Tasman Sea. The East Australian Current brings warmer waters down the east coast, raising ocean surface temperatures in the Tasman Sea relative to the neighbouring Bass Strait and Southern Ocean. When these low pressure systems develop over the western Tasman Sea, that warm water provides a lot more energy through evaporation.

When all the elements align, with a cold front and its associated cold air mass moving over warm water, beneath an upper-level low in the same place providing reinforcement, a deep and complex low-pressure system can develop.

Difficult to predict

The Bureau of Meteorology usually has several days’ indication that a system like this may form, but development of multiple low-pressure centres at the surface makes it tricky to predict exactly where local impacts will strike.

These small-scale low-pressure centres influence exactly where the heaviest rain or strongest winds will be, as do features of the landscape like mountain ranges.

While we can make broad predictions of what may be on the way, it’s not until we get closer to the event that we can really start to be more specific about rainfall totals, wind speeds, and so on.

The Bureau gets minute-to-minute readings from our Automatic Weather Stations, but we have the ability increase the frequency of some of our measurements (for example, at the moment we have increased the frequency of weather balloon releases at Hobart airport), to get additional information about the atmosphere.

This system will move fairly slowly over the next couple of days, and different elements will impact different parts of Australia.

We’ve got cold air, wind and showers over Victoria and southern New South Wales at the moment, but there are parts of the east coast that are still quite warm today. Tasmania is starting to see windy conditions in Hobart and rain developing, and potentially heavy rain through the east of the state over the next couple of days.

Once the cold air moves further north into NSW we’ll expect snow at lower levels as far north as the Central Tablelands, and then as we move into the weekend the low pressure system will move out into the Tasman Sea.

We’ll then start to see swell increase, as the ocean responds to the weather system. Heavy swell and hazardous surf conditions could push well north along the NSW coast and potentially into southern Queensland by early next week.

Weather warnings

Currently, severe weather warnings for wind have been issued across parts of South Australia, Victoria, New South Wales and Tasmania. Heavy rain warnings and flood watches are in place in Victoria, and flood watches and warnings are current in Tasmania as well.

https://www.facebook.com/plugins/video.php?href=https%3A%2F%2Fwww.facebook.com%2Fbureauofmeteorology%2Fvideos%2F1831136796950212%2F&show_text=0&width=560

Other specific warnings provide important information for those on the land – the Bureau has alerted sheep graziers, for example, to the impacts of cold, wet and windy conditions on exposed livestock.

While these warnings are all fairly standard for this kind of weather system, always follow the advice of emergency services. We’re the weather experts, but they’re certainly the experts on preparing for hazardous weather!




Read more:
Too wet? Too cold? Too hot? This is how weather affects the trips we make


The ConversationWe’d also advise everyone to keep up with the forecasts and warnings on the Bureau of Meteorology over the next few days.

Adam Morgan, Senior Meteorologist, Australian Bureau of Meteorology

This article was originally published on The Conversation. Read the original article.

Advertisements

Decline of traditional media


Should the threat to traditional media from the internet really be a cause for concern?

The new social media — blogging, Facebook, MySpace, Twitter, and YouTube are current faves — revolutionising the publishing world, for better and worse. Let’s look at both the better and the worse in perspective.

The current tsunami of personal choices in communication is slowly draining the profit from mainstream media. These media traditionally depend on huge audiences who all live in one region and mostly want the same things (the football scores, the crossword, the TV Guide, etc.). But that is all available now on the Internet, all around the world, all the time.

One outcome is a death watch on many newspapers, including famous ones like the Boston Globe. As journalist Paul Gillin noted recently: “The newspaper model scales up very well, but it scales down very badly. It costs a newspaper nearly as much to deliver 25,000 copies as it does to deliver 50,000 copies. Readership has been in decline for 30 years and the decline shows no signs of abating. Meanwhile, new competition has sprung up online with a vastly superior cost structure and an interactive format that appeals to the new generation of readers.”

Traditional electronic media are not doing any better. As James Lewin observes in “Television audience plummeting as viewers move online” (May 19, 2008), mainstream broadcasters “will have to come to terms with YouTube, video podcasts and other Internet media or they’ll face the same fate as newspapers.”

Radio audiences have likewise tanked. Overall, the recent decline of traditional media is remarkable.

Some conservative writers insist that mainstream media’s failure is due to its liberal bias. But conservatives have charged that for decades — to no effect. Another charge is that TV is declining because it is increasingly gross or trivial. True enough, but TV’s popularity was unaffected for decades by its experiments with edgy taste.

Let’s look more closely at the structure of the system to better understand current steep declines. Due to the low cost of modern media technology, no clear distinction now exists between a mainstream medium and a non-mainstream one, based on either number of viewers or production cost. Today, anyone can put up a video at YouTube at virtually no cost. Popular videos get hundreds of thousands of views. Podcasting and videocasting are also cheap. A blog can be started for free, within minutes, at Blogger. It may get 10 viewers or 10,000, depending on the level of popular interest. But the viewers control that, not the providers.

The key change is that the traditional media professional is no longer a gatekeeper who can systematically admit or deny information. Consumers program their own print, TV, or radio, and download what they want to their personal devices. They are their own editors, their own filmmakers, their own disc jockeys.

Does that mean more bias or less? It’s hard to say, given that consumers now manage their own level of bias. So they can hear much more biased news — or much less. And, as Podcasting News observes, “Social media is a global phenomenon happening in all markets regardless of wider economic, social and cultural development.”

Understandably, traditional media professionals, alarmed by these developments, have constructed a doctrine of “localism” and, in some cases, called for government to bail them out. That probably won’t help, just as it wouldn’t have helped if the media professionals had called for a government “bailed out” of newspapers when they were threatened by radio, or of radio when it was threatened by TV. Video really did (sort of) kill the radio star, but the radio star certainly won’t be revived by government grants.

Still, the news is not all bad. Yes, new media do sometimes kill old media. For example, no one seriously uses pigeon post to send messages today. But few ever thought birdmail was a great system, just the only one available at the time. However, radio did not kill print, and TV did not kill radio. Nor will the Internet kill older media; it will simply change news delivery. Sometimes in a minor way, but sometimes radically.

Media that work, whether radio, TV, newspapers, books, blogs, or any other, thrive when there is a true need. Today’s challenge is to persuade the consumer to look at alternatives to their own programming decisions.

Denyse O’Leary is co-author of The Spiritual Brain.

The original news article can be viewed at:
http://www.mercatornet.com/articles/view/decline_of_traditional_media/

Article from MercatorNet.com