Australia's Bureau Of Meteorology Is Dropping Confusing Weather Terminology

Australia's weather bureau is clearing up confusing terminology in its forecast reporting. When it comes to rain, apparently terms like "scattered", "isolated" and "patchy" aren't descriptive enough, and are being replaced with percentage figures.

Weather image via Shutterstock

The ABC reports that the Bureau of Meteorology's change is occurring because the current terminology is too ambiguous, and that terms like scattered, patchy and isolated don't do enough to describe the possibility of rain in any given area.

Those loaded adjectives are being replaced with the cold and distant terms "very high", "high", "medium", and "slight". Those terms, along with the use of no mention of rainfall at all, line up with the chance of rainfall expressed as a percentage of possibility:

  • Very high: Over 80 per cent chance of rainfall
  • High: 60 to 80 per cent chance of rainfall
  • Medium: 40 to 60 per cent chance of rainfall
  • Slight: 20 to 40 per cent chance of rainfall
  • No mention: 0 to 20 per cent chance of rainfall

It's good to see a little more clarity in the BoM's wording, but it doesn't change the fact that micro- and mesoscale (local) daily weather is, even at its best, unpredictable. (That's an important distinction from weather science more generally, which is concerned with weather on a larger scale and longer timeframe, and has an excellent track record.)

In any case, the extra level of granularity that the five-step system allows means that weather reports will now be slightly more descriptive, even if they are a little drier and less eloquent. The difference between slight and medium might be enough to get you carrying an umbrella, and the difference between high and very high might change your mind about that morning walk to the bus stop or train station in the first place. [ABC]

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    Who relies on the BoM these days? I always look at my phone, Google Now tells me the chance of rain and the expected wind speed at any given time throughout the week. But good to see the BoM get with the times.

      You spastic. Where do you think those services get the data from? Thin air?

        probably the ironicaly often inaccurate

        Its great to see such a retarted response from such a retard like you. A simple search for "Google weather" (heres the link since its so tough: would show you that Google Weather is sourced from ACCUWEATHER. Foot mouth disease much, or just plain fucking stupid? Dumb ass.

          From what I can gather Accuweather does indeed get its data from government sources, especially for places like Australia, but even in the US where they also collect some of their own. I think all they do it make their own forecasts using the data they're given, just like TV weather people used to: the raw data for the Australian stuff would all come from the Bureau of Meteorology.

          Last edited 07/10/14 6:35 pm

      I always use BoM - it's more accurate than Google - can check radar etc.

      Google Now has the most useless weather information I've ever seen

      Last edited 07/10/14 4:23 pm

        My experience has been totally opposite. I've never had a problem with it.

          Each to their own... I turned it off after the 3rd time it told me 20 and sunny when it was raining outside

    Great, now i have percentages that are going to wrong instead of descriptive words that are wrong. This will make life so much easier. Basically ignore what they say and stick your head out the window and see what the weather is like knowing that certain seasons will produce hot weather and wet weather on the same day. As for melbourne, 4 seasons in one day is what they say and it is generally correct.

      The head out the window thing doesn't really work though in spring and autumn, it's to chaotic to judge, but not too chaotic for the weather service... and I find people are so stupid generally that if they see the sun shining they're going to be wearing T-shirts and shorts no matter how chilly it is, AND cranking up the air-conditioning in the office.
      When people's brains are limited to the level of sunny=warm, they need all the help they can get with actual weather science.

    I'd have thought that patchy or isolated would be better understood by people who don't get maths and wont understand percentages of which there are plenty out there.

    Nothing beats the accuracy of the NAIPS system setup for all pilots. Basically do a weather check between three airports surrounding your area and your guaranteed accurate weather for that area for the next 24 hours, that is no joke. Peoples lives depend on it. Each forecast is bang on for 10nm surrounding the airport.

    But the data used is the same data the BOM relies on too, but the advantage is its curated locally by a meteorologist so modifications and personal experience and skill is added. Its not generalised over a large area like the civilian forecast.

    Amazingly most of the data comes from automated weather machines, and they are amazing accurate including the cloud cover percentage, and different altitudes they apply to. Aipressure at difference altitudes, air temp, what height the ice will be a problem. Most QANTAS planes have a weather station in their tail that beams a cross section of the weather details in realtime to BOM as well.

    Our weather system is world class and one of the best.

    Yeah, those pesky people and their hard questions. Things like, why do you get the forecast so wrong so often. Why is BOM manipulating data to show a warming pattern when the data really shows a plateau or cooling?

    This is the dumbest idea they have ever had. Does that mean now you need a forecast for specific areas in the metro area? The city weather (rain) can vary so much in different suburbs how can one percentage cover the whole metro area. At least with percentages no one can really quantify the blame for bad weather on the bureau

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