A rapidly intensifying storm is poised to sweep across the U.S., threatening widespread disruption for nearly 200 million people.

What does the weather term mean, how do the storms form and why are they so dangerous?

A category four tropical cyclone with destructive wind gusts in excess of 250km/h has made landfall in Far North Queensland.

Cyclone Narelle could bring wind gusts of up to 285km/h, the Bureau of Meteorology said. Residents in Queensland and the Northern Territory have been urged to stay alert. Tropical Cyclone Narelle is expected to bring severe impact to Far North Queensland on Friday,

The storm, which made landfall this week in Libya, is fairly infrequent, with only a dozen forming between 1982 and 2003.

Tropical Cyclone Narelle is lashing Australia's far north, with residents told to shelter in place as the powerful storm batters the flood-ravaged region.

Satellite imagery recently showed what looked strikingly like a tropical cyclone barreling toward Alaska.