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.

In my previous blog post I pointed out that tropical lows and cyclones don't have fronts like the lows we're used to around NZ, but rather, a core of warm air near the centre. I'd like to follow up by further contrasting tropical and mid-latitude lows, and looking a bit more closely at tropical cyclones and how they can affect our weather in New Zealand.

When tropical lows fully develop into cyclones they become the most damaging of tropical weather features. There are three main reasons for this: