Long admits that despite astute calculations and analysis, it's not hard to make forecasts that end up being wildly inaccurate.

The use of more powerful computers in recent years, however, has helped the Bureau's scientists to get it right more often.

Data from the world's national meteorological services (from ground stations, upper air observations, satellites, ships, buoys) is fed daily into a super computer, checked for accuracy, and mapped onto a three-dimensional grid.

Each grid point represents a snapshot of atmospheric pressure, temperature, moisture and wind speed.

The weather can then be predicted by combining data from these variables.

In Victoria alone, there are 80 weather stations that report on temperature, wind, pressure, relative humidity, rainfall and other weather parameters at least once every 30 minutes.

Upper-level observations are taken from 46 stations around Australia and Antarctica showing the winds at various heights in the atmosphere, with some also reporting the temperature and humidity.

Some stations record this data four times a day, while others only take observations once a day.

All the surface observation data goes into the computer models to create a picture of the current state of the atmosphere for each grid point around the globe.

The model then makes trillions of computations to figure out what will happen at each grid point up to seven days in advance.

The global model is run twice a day and the regional model four times a day.

With the complexity and volume of data constantly increasing, the Bureau's super computer requires regular upgrades.

But no matter how good the technology, mistakes will always be made.

"Some days no matter what you do, you might have done your best but it didn't pan out for whatever reason," Long says.

"A day like last Wednesday is a good example of our limitations.

"We forecast 39 degrees but we only got to 32.6 at about 9am after the change came through early morning, instead of after lunch.

"If that change had come through at 5am or 6am, it might have only got to 27.

"The difference between a cold front moving through in a four-hour plus or minus period can be the difference between 39 degrees and 25 degrees and people think, 'Wow, a temperature error of 10 or 15 degrees, that's pretty terrible, what are they doing?' but it has to be looked at in context.

"There are so many things that can make a front go a bit earlier or later.

"If the northerlies are a little bit stronger it won't push through, if they're a little bit weaker it will push through.

"There are just so many different variables.

"You've got to realise with forecasting you're never going to get it 100pc right all the time.

"The atmosphere is just too chaotic."

But Long says that no matter how good computers become, she cannot foresee a time when they will replace meteorologists.

"Computers can do all the calculations really well but they can't turn all that scientific data into one sentence that sums up what the weather is going to be," she says.

"They can't tell a concreter if it is going to rain so he knows whether or not to pour that concrete slab.

"As good as computers are — and we certainly need them as a tool — there will always be a place for human involvement."

Long, 30, who remembers driving her parents crazy as a kid who always wanted to know how the world worked, says every time she tells someone she works for the weather Bureau there is an instant reaction.

People always want to voice an opinion or make a comment.

"The weather impacts on everybody," she says. "It's just part of everyone's day and it's something that brings people together.

"People want to know. People are interested. It's the standard conversation topic.

"You don't know what to talk about so you talk about the weather. It's sort of the filler."

Long says the pressure on the Bureau to get the forecast right intensifies, like a category 5 tropical cyclone, on public holidays such as Christmas Day, Melbourne Cup Day and Anzac Day, or for events such as the Sydney to Hobart yacht race — "these sort of big days when you know people are going to be out and about doing things, having barbecues".

"Those are the days when people will pay attention to what the weather is doing and they'll look at the forecast a week or so in advance."

The Bureau, which celebrated its 100-year anniversary last year, provides weather forecasts for more than 170 cities and towns and 60 forecast districts across Australia.

The observation system involves 58 bureau-staffed stations that undertake a comprehensive program of surface and/or upper-air meteorological data collection; a network of more than 800 stations recording surface observations either from automatic weather stations or via contract observers; some 6000 volunteer rainfall observing stations; approximately 100 volunteer ships taking marine weather observations; and a range of other networks and facilities such as weather-watch radar, lightning detection, solar and terrestrial radiation, satellite data reception, ozone and marine observations from drifting buoys and sub-surface floats.

In addition to the conventional meteorological variables such as wind, temperature, humidity, rainfall and pressure, specialised data on radiation, ozone and other chemical constituents relating to the greenhouse effect and depletion of the ozone layer are collected, as well as data on ocean temperature, salinity, waves and currents.

And in a bid to continue to provide the most accurate weather forecasts possible, the Bureau last year replaced five obsolete radars with modern, state-of-the-art weather surveillance radars.

Images taken from Melbourne's new high-resolution Doppler radar, which are available to the public via the internet, are now updated every six minutes, instead of at the previous 10-minute intervals.

Long says the Bureau is well aware it will face a storm of fury if mistakes are made regularly, so staff do their best to be accurate.

Forecasters in Melbourne work as a team, with a senior forecaster and other forecasters with responsibilities for aviation, public weather and severe weather. All the forecasters discuss the weather situation after analysing the latest data, with the senior forecaster having the final say in setting the forecast policy for the day.

The pressure to get it right never changes, unlike the weather.