I am curious how you figure that out , I think you might be barking up the wrong tree!!!
There is a handy little
New Zealand surf guide book out that you could buy. It might help and like everywhere inthe internet world there are surf forecasts.
The South Island west coast is smashed by every thing that gets past the bottom of
Australia generated by Antarctica and the roaring 40s with no real access south of Greyhound, it is Fjord land, contend with Ocras and great white sharks.
The east coast south Island is great but the swell making storms are crossing to South America can be brilliant or huge or both or flat and can have epic on shore winds.
North Island west coast gets the same SW swell cleaned up and pointed at all parts of the west coast, Taranaki has its round coast taking swell from everywhere, .
There often more than two cyclones per year between
Queensland and
Fiji we have booked seven for this year.
NZed is the land to make your own discoveries. so I am not telling over here on my side of the ditch if I told you I would be Pakeha pancake on my next trip over there.
Also much access is through private farm lands so you need to know someone or make a polite request of the farmer. These spots are very protected because careless individual actions have stopped access.
Search and you shall find, the weather if you don't like it, wait a couple of hours

I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun! 冲浪爷爷