Apologies Carla, something just as simple as a tag not being added when we posted. Thanks for letting us know, we’ve now fixed this.
– WW

Hi Sylvia,

Take a look at the current video on our homepage as I talk about how the large high pressure zone north of NZ is positioned to pull down the much warmer subtropical airflows across parts of NZ. So that’s the first step to bring in the heat – the second step is delivering that airflow as a windy nor-wester. As air is pushed over the eastern North Island ranges it dries out as it rises, then simply the motion of that air descending out east warms it up even further. A double whammy to bring in summer heat in spring. It can happen at any time of the year but spring is often when it gives us our first “hot days” since the previous summer.

Cheers,
Philip Duncan

Hi there, Last year Niwa talked about La Nina forming for the entire year – and then it didn’t form. WeatherWatch spent that same year publicly saying we didn’t think La Nina would form. We don’t monitor what Niwa forecasts (other than the MSM coverage they get) as despite being a public Government Agency Niwa actually aggressively directly competes with us (even the Commerce Commission has had to investigate them). So instead we monitor, and are guided by, the Bureau of Meteorology (BoM) out of Australia as they cover our part of the world in more detail than Niwa and they provide open data and maps, not just opinions. BoM was most accurate last year about their skepticism that La Nina would develop when Niwa was so sure it would. This year BoM is saying La Nina is borderline – and so if we do have a brief La Nina period it will create more rain north of NZ and more low pressure. But whether that weather in the tropics can then reach NZ is an entirely different question. There is always the risk of an ex-cyclone in NZ any given year. Check out our recent ClimateWatch video as it breaks down the irregular shape of the polar vortex at the moment and how that’s enhancing our spring weather: https://www.youtube.com/watch?v=0Sha2cnfhME.

If the spring westerly winds continue to dominate NZ then even if La Nina forms there remains questions about how it can affect NZ (La Nina is measured at the tropics and NZ is halfway between the tropics and Antarctica, so if westerlies are blowing here it means high pressure is likely just north of NZ – and high pressure blocks/limits rain makers).

Cheers
Philip Duncan