Skip to navigation | Skip to content

Lightning storms in the Top End

People living in the Top End of Australia say they go a bit 'troppo' or crazy as the heat and humidity builds towards the wet season. When the storms finally break, tropical northern Australia will be treated to some of the most spectacular lightning shows in the world.

In just a few hours Darwin can experience as much lightning as Perth does in one year.

In just a few hours Darwin can experience as much lightning as Perth does in one year. (Source: Michael Bath - Australian Severe Weather Association)

The Top End of Australia is one of the most lightning prone areas on Earth. At this time of year, the region is about to get it's annual dose of massive thunderstorms. Last summer a single thunderstorm over Darwin produced an incredible 1,634 lightning flashes in just a few hours. Perth only gets this much lightning in an entire year.

Thunder storms can cause chaos, as the Northern Territory's Power and Water Utility knows only too well. Manager of Network Maintenance Chris Yam said that for the first few months of the wet season, there will be lightning most nights. About 40 per cent of all the electricity outages are caused by lightning, and burn marks are frequently seen on local power poles and other tall structures.

In Australia, lightning accounts for 5 to 10 deaths and well over 100 injuries annually, according to the Bureau of Meteorology (BoM). The BoM predicts these figures are likely to increase, with the growing number of retired people engaged in outdoor, recreational activities such as walking, cycling, golf, fishing, boating etc. Of the many lightning strike injuries each year, about 80 result from people using fixed telephones during thunderstorms when the phone system may become highly charged near where lightning is striking. Related injuries may include hearing damage, burns, or even electrocution.

Fact file:

When: Summer

Where: Northern Territory, Western Australia

Other info: A single thunderstorm in 2002 in Darwin produced an incredible 1,634 lightning flashes in just a few hours.

The local Aboriginal people had a fiery Dreamtime spirit called the Lighting Man who carried a lightning bolt across his shoulders, and stone axes with which to make thunder.

^ to top

Extreme seasons

The extreme seasonality of the Top End has profoundly shaped the natural environment. After the hot dry season, the land is blackened by fires which burn throughout the winter across the tropical woodlands.

With the coming of the rains, cycads, onion lillies and other plants burst into green new growth. Frilled neck lizards appear and begin hunting for a mate. They are not worried by the thunderstorms which rage around them, because these storms bring the rain which begins a new phase of growth in the Top End. In Kakadu National Park, the rains pour off the escarpment in massive waterfalls, bringing moisture to the parched landscape.

^ to top

Hot spot

Why is Darwin such a lightning rod? Dr Michael Foley from the Bureau of Meteorology's Severe Weather Section says it is a combination of factors.

Firstly, being a tropical area, there is a strong amount of energy coming in from the sun, which heats the ground and causes the air to rise. Being close to the coast, this air is quite moist.

As the moist air travels up into the sky, it cools and eventually forms ice crystals, which become the seeds of lightning once they are inside clouds. A storm is often triggered by a sea breeze moving inland, and colliding with hotter air.

Meteorologists love doing storm research in Darwin. Professor Steve Rutledge from Colorado State University is a world expert on lightning and says there is no finer place to do his research than Darwin because of the storms, and also the fact that the region experiences two distinct weather regimes.

In November at the beginning of the Wet, the storms are very intense, with strong updrafts travelling up to 50 metres per second, and plenty of lightning around. Then in January when the monsoon starts to set in, the convection (movement of heat through the air) gets weaker. This results in less lightning but lots of rain, a transformation from continental tropical convection to weaker convection.

^ to top

How is lightning created?

How lightning is actually created inside a cloud is still the subject of active research. Professor Rutledge said that for a storm to become a thunderstorm (to produce lightning and therefore thunder), it needs to produce lots of ice in the atmosphere. This is what happens in Darwin early in the wet, when energetic storms take raindrops and raise them up to where they can freeze. These ice particles, he says, collide with one another, and they become charged.

A negative charge is acquired by the larger particles, while the smaller ones become positively charged. Heavier ice particles tend to move down to the bottom of the cloud and so most of the negative charge is transferred down there. The top of the cloud tends to remain positive.

For a while, the atmosphere acts as an insulator for the two charged parts of the cloud. But eventually the charge difference becomes so great that the insulation breaks down, the electrons flow towards the positively charged area, and you get a lightning stroke produced as the accumulated electricity is discharged.

Surprisingly, only about 10 per cent of lightning goes from cloud to ground (the most familiar kind of lightning). Much more common is cloud to cloud lightning, or cloud to air lighting. Occasionally, lightning will go up from the ground to the cloud. This can happen when positively charged areas of the storm are near the ground.

^ to top

Global thermometer

Lightning research can be difficult, expensive and even dangerous. Why then study it? One reason, says Professor Rutledge, is to develop an early warning system which could predict how severe storms will behave in the first few hours, a branch of meteorology called "now-casting".

A unique signal of a severe storm is that it has a very high intercloud flash rate, that is, cloud to cloud lightning, but at the same time, produces few cloud to ground flashes. If lighting from a particular storm could be observed both from above, via satellite, and from the ground, this combined information could indicate if the storm is going to become severe, or just maintain as an ordinary rainstorm or weak hail storm.

Professor Rutledge says the hope is that one day, there will be satellites which measure lightning around the globe routinely, to enable these kinds of predictions to be made.

Another, more speculative area of research is using lightning to predict global warming, by measuring how storms are changing over time. If the lowest few kilometres about the surface of the earth is warming up, it will tend to create more thunderstorms which are more intense, globally. This low level warming would also lead to more intense convection, and therefore more lightning. It may be that lightning could be used as a kind of 'global thermometre' to measure planet-scale temperature changes.

"We don't know if that is really going to play out in a global warming scenario," says Professor Rutledge. "We'd like to be able to document global lightning for a decade and then see if it is increasing with the increasing temperature. If we got more lightning, that would tell us if we are getting more intense thunderstorms, as opposed to more weaker convective storms around the earth [which would indicate that global temperatures were increasing]."

In the meantime, Darwin will continue to attract researchers from around the world who come to study the spectacular storms and the stunning lightning shows they create.

Lightning facts

  • When struck, people do not glow or 'fry to a crisp' but the heart and breathing are often affected.
  • Only about 30 per cent of people struck actually die, and the incidence of long-term disability is low, particularly when appropriate first aid is applied promptly.
  • If your clothes are wet, you are less likely to be seriously injured if struck, as most of the charge will conduct through the wet clothes rather than your body.
  • Average lightning bolts carry a current of 10,000 to 30,000 amps. An average radiator draws 10 amps.
  • Lightning can, and often does, strike more than once in the same place.
  • Worldwide, thunderstorms produce approximately 6,000 lightning strikes every minute.

- from Emergency Management Australia and the Bureau of Meteorology

^ to top

Further info and credits

How lightning forms

Top End seasonal calendar

Lightning and atmospheric electricity research

Michael Bath's Australian lightning images

Severe Weather Association

Australian Bureau of Meteorology

Special thanks to:
Michael Bath and the Australian Severe Weather Association for permission to reproduce the superb lightning images
Dr Michael Foley, Bureau of Meteorology, Professor Steve Rutledge, Bureau of Meteorology
CSIRO for permission to reproduce lightning image, Northern Territory Power and Water Utility.

Tags: storm

^ to top

Published 10 December 2002