Before Cyclone Tracy bore down on Darwin in 1974, forecasters were mapping its trajectory on pieces of old fax paper.

Cyclone facts: Cyclones form over warm sea temperatures - this gives them moisture

Cyclones form over warm sea temperatures - this gives them moisture Special atmospheric conditions like monsoon troughs give them energy

Special atmospheric conditions like monsoon troughs give them energy The Northern Territory cyclone season is November to April

The Northern Territory cyclone season is November to April There are 5 categories of cyclones with 3, 4 and 5 being severe

There are 5 categories of cyclones with 3, 4 and 5 being severe A category 3 has wind gusts in excess of 160 kilometres per hour

A category 3 has wind gusts in excess of 160 kilometres per hour A category 4 will cause significant structural damage

A category 4 will cause significant structural damage A category 5 has wind gusts in excess of 280 kilometres per hour - roughly the speed of an aircraft as it is taking off

A category 5 has wind gusts in excess of 280 kilometres per hour - roughly the speed of an aircraft as it is taking off Houses in the NT are built to withstand category 4 winds - not category 5

A grainy image came from two satellite dishes on the roof and was printed on paper at the Bureau of Meteorology (BOM). Forecasters then manually drew lines on the printout to chart the path of the cyclone.

BOM senior meteorologist Ian Shepherd - a 30-year veteran of the job - said if one of the satellite dishes malfunctioned, the forecasters had to to fix the equipment themselves, as well as providing public warnings, and keeping on top of incoming data.

Forty years later, Australia uses satellites from Japan, Europe and the United States to gather data used in forecasting, and satellite technology is a leading tool of forecasters.

"It's an almost unbelievable change," Mr Shepherd said. "There's 40 years of development. We've got this tremendous global cooperation between countries and all the countries will exchange meteorological data freely."

Bureau of Meteorology technical officer David Sinclair prepares to release a weather balloon in Darwin. ( ABC News: Joanna Crothers )

Infrared satellites track cyclones by their surface temperatures, meaning forecasters can track a cyclone's course and speed through the night.

"Back in 1974 there was only one weather radar and it was located at Darwin Airport," Mr Shepherd said.

"Now there's a whole network of those radars being established around Australia. There's a new generation of radars which are being installed now.

"They not only detect the precipitation and the rainfall, but they also can detect the wind speeds that are occurring in the atmosphere as the cyclone approaches."

There are even three dimensional radars which tell meteorologists where the most localised damage will occur.

The weather balloon has been used for years, but it remains an essential piece of equipment, BOM technical officer David Sinclair said.

"It's absolutely critical," he said. "The data from the weather balloon gives you a profile of the atmosphere and because we put those radiosondes up every 12 hours it gives you an opportunity to track how the atmosphere is changing throughout the day and throughout the week."

Mr Sinclair said forecasters use data from all the weather balloons across Australia and input it into modelling.

'Tracy formed in a sweet spot and took a unique path'

The official account describes Cyclone Tracy as a category 4 cyclone. But some meteorologists now believe the cyclone was a category five shortly before it made landfall at Darwin, according to Mr Shepherd.

He said it gathered energy from the warm waters north of Australia for two days.

"It formed in I suppose what you might call a bit of a sweet spot," he said.

"It's well north of Australia and closer to Indonesia than the Australian coast in the Arafura Sea.

"That area is a good sort of spawning ground for cyclones.

"They say that in Tracy there was a fridge planted into the water tower next to the airport at a height of 50 metres so it gives you an idea of its strength.

"Normally cyclones will weaken once they interact over land, but Tracy took this unique track which took it around the end of Bathurst Island.

"It turned direction exactly around the coast of Bathurst Island then took a beeline directly for Darwin, which is pretty much the worst case you could expect.

"To repeat that again would be extremely unlikely."

With the advancement of computer technology, BOM meteorologists are confident a cyclone will never form and cross the coast of the mainland without warning.

"The bureau has a very sophisticated system in place to provide advance warning and all we ask is that people listen to the advice of the emergency authorities and prepare," Mr Sheppard said.

He said people could now get emergency information quickly from a number of different platforms.

"People can access that information by the internet, by mobile devices, radio, TV," he said. "There's a plethora of ways."