December & Summer climate outlook for NZ (+8 Maps)


WeatherWatch.co.nz has issued its first ever seasonal forecast thanks to IBM and it paints a picture of continuation of our current weather pattern.

*Please note this was originally published November 27*

Put briefly much of the North Island looks both warmer and drier than average while the South Island leans a little cooler and wetter (at least in the west and south of the island). Taranaki and around south Wairarapa may be the only areas a little cooler and wetter in the North Island.

Put Simply:

  • North Island leaning drier and warmer than average this summer
  • South Island's West Coast leaning wetter and cooler than average

Rainfall-wise the eastern South Island remains a little bit of a question mark (you'll notice as asterisk in the summer rainfall map) with average to even slightly above average rainfall forecast - but this is 100% down to the angle of wind flows over the months ahead a slight shift a little more westerly means Canterbury may also be looking at a warmer and drier than normal summer (keep in mind just 10mm of extra rain could help tip Canterbury "wetter than average" - which could come from just afternoon downpours, which can also be very hit and miss).

WeatherWatch.co.nz says with Australia's drought truly set in it appears the upper North Island of New Zealand is catching some of their high pressure leading to a drying out phase in the North Island over the past few months. These highs are also increasing the sub-tropical (warmer than normal) airflows over NZ.

However an extra stormy Southern Ocean this spring is likely to continue right through December and maybe January too. This, in combination with mild airflows further north, means the South Island may get some heavy rain events on the West Coast and some spillover into Southland and Otago with some cooler air flows out of the Southern Ocean at times.

Remember this isn't a weather forecast, it's basically a climate outlook pushing all the forecasts into one map to give an average of temperatures and rainfall. It's not yet a perfect science so this outlook is designed to help with long term decision making but we know there's room for improvement so please let us know what we could do better - and clearly at the end of both December and Summer we would very much welcome your feedback on accuracy - and don't hold back! Our aim is to get better and better in the tricky world of climate outlooks. 

WILD CARD EFFECT:
With New Zealand being such a relatively small country compared to the water all around us the one thing that can throw any seasonal and monthly forecasting out is a single air pressure system that can stall over us. If it's a high it can increase dry and hot weather. If it's a low - such as a tropical storm - we may get over a months rain in one day in a region that was forecast to be dry. This is what we call the Wild Card Effect and gives those who need rain a silving linging that relief may be coming even if not in the long term outlooks.

WINNERS AND LOSERS:
Always a bit tricky trying to nail this one as it's ofen subjective but we do think there are a few clear winners and losers from this outlook:

  • POSITIVE: Great news for camp grounds across the North Island and upper and eastern South Island
  • POSITIVE: Most main cities look warmer than normal this summer - many may like that
  • NEGATIVE: Concerning news for dairy farmers and those who rely on rain water, especially in the upper half of the North Island
  • NEGATIVE: Auckland city may well have water shortages again, with a call for people to save water (as the water shortage the city had back in winter still hasn't been reversed).
  • NEGATIVE: Windy weather may linger into January this year for some regions due to an uptick in westerly quarter winds over NZ, especially from the lower South Island southwards.

RAINFALL - DECEMBER:

RAINFALL - DECEMBER:

RAINFALL - SUMMER MONTHS (DEC, JAN, FEB)

RAINFALL - SUMMER MONTHS (DEC, JAN, FEB)


TEMPERATURE TRENDS - DECEMBER

TEMPERATURE TRENDS - DECEMBER

TEMPERATURE TRENDS - SUMMER MONTHS (DEC, JAN, FEB)

TEMPERATURE TRENDS - SUMMER MONTHS (DEC, JAN, FEB)

- WeatherWatch.co.nz - Proud to be an official IBM business partner 


Comments

Love your site but

could you make the font bigger please :) Cheers

100% - wil do next update.

100% - wil do next update. Great feedback, thanks!

- WW

weather patterns

oh I don't think nz will have another failed tropical season too

weather patterns

not according to NIWA its going to change a round later and by what happen at the beginning of the year that would be fair

Niwa makes loads of big long

Niwa makes loads of big long range forecasts that fail to happen - they recently predicted a historic major nationwide Antarctic blast ...that never happened this spring. The reason we've moved into longer range forecasting is due to public demand for an alternative. We ignore Niwa forecasting, but do trust scientific long range forecasting from Australian, US and other global scientists since Niwa became so commercial and aggressive in 2013 instead of behaving like a tax funded Crown Research Institute. 

Cheers

WW

Ssw

I’ve been waiting and wanting you guys to bring up the sudden Stratospheric Warming event that occurred over Antarctica this spring, that was what niwa were indicating would push the cold outbreak up over nz. It appears at least partially responsible for the wet spring in the south and west of the South Island and the stalled southern ocean low currently churning away. How often do those lows stall?!, especially in spring, they normally truck along in the westerly conveyor belt... Cheers, Ben.

Hey Ben, Niwa should NEVER

Hey Ben, Niwa should NEVER have linked a climate moment to a weather moment the way they did in early spring. Looks as though they backtracked in the end on their statements after realising their huge cock up by making such a dramatic weather forecast when it was really a CLIMATE issue. Lows like this one do stall from time to time, especially in the slower months (Nov to Mar) when there's not the same big westerly flow. But this is unusual based on how long it is stalling. Since they forecast (using 200 million NZ tax dollars) a cold, wintry, spring - NZ actually had the opposite with only the exceptions of Southland and the West Coast.

Anyone with half a brain who takes the time to really look can see Niwa is targeting MetService (tax funded Agency vs tax funded Agency) simply to make clickbait/ratings. Niwa is cannibilsing their own credibility now by hyping all events and never being accountable to those that fund them - the NZ taxpayers and public.

Cheers
PhilD

Thanks for the reply Philip.

Thanks for the reply Philip. I agree with the strange set up re funding and competition between government agencies. Hope your not offended if I offer some advice from afar. Try not to let your argument become vitriolic, it doesn’t lend any credence to your position regardless of how right you are. Yes, I know you have to shout to get heard on the Internet but the world needs less shouting! You don’t have to put this comment up, I go onto weather watch daily for your video updates to get a good overview of what’s going on. I work in the mountains ski guiding around Mt cook area through the winter, and hunt waves down in the catlins, so the weather isn’t just what happens out the window for me. I want to see WW do well! Merry Xmas....Ben