What do Irene, Osai, Tam and Xavier all have in common?
tropical cyclone
Understanding Tropical Cyclone and Cyclone Track Maps
How do I understand a tropical cyclone track map?
Tropical cyclones: extra-tropical transition
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.