What do Irene, Osai, Tam and Xavier all have in common?

How do I understand a tropical cyclone track map?

Written by Steve Ready Meteorologist

On average, about nine tropical cyclones form in the South Pacific tropics between November and April each year. Three or four of these leave the tropics and nearly all of them undergo a marked transformation to a mid-latitude cyclone – a completely different weather system – before they reach New Zealand.