The Swiss Cheese Effect - How to read NZ's Seasonal/Monthly forecasts and get more from them

We all know the generic forecast that often gets it wrong. "A dry weekend" says the weather - then you get a downpour and your gutters overflow. Welcome to New Zealand and why forecasters age here faster than most nations on earth!

NZ's location - half in the Roaring Forties and parked near the cyclone centre of the South Pacific - means our weather is all over the show. It doesn't help that when Australia catches a drought, northern New Zealand (at least right now anyway) catches a Big Dry. has a formal yet informal way of tracking developing droughts. "We use the term 'big dry' before we get to the point of using the dreaded 'd' word" says head forecaster Philip Duncan. "Right now we have a big dry forming in the upper North Island with rainfall across 2019 below normal and lately the hotter and drier weather from Aussie and the tropics has only made this worse".

After a decade of people force-funded and confused by Government Agency NIWA's highly confusing and rarely accountable tax-paid-for seasonal forecasting we last month teamed up officially with global weather giant IBM to produce monthly and seasonal/climate outlooks specifically for NZ in the most detailed way ever - in fact, we're blowing tax-funded-and-owned-NIWA out of the park by using the world's most *accurate weather data* - a statement which IBM can formally back up. Interesting how NZ's mainstream news media (who all buy from the NZ Government) don't seem concerned on any level at all about accuracy when they report big weather news headlines from NZ Government forecasters just to get a click. is now going head to head with Niwa's seasonal forecasts - click here to view our more simplistic, accountable, approach

WeatherWatch is now taking clunky massively-tax-funded Government agency NIWA head on since they decided to ditch public good from those who tax fund their entire existence to instead focus on being aggressively commercial towards MetService (another Government agency we all have to tax fund) - as an offside, that means NIWA is also attacking private sector WeatherWatch using our and your tax dollar contributions to them. To call that "sick and wrong" is an understatement.  NIWA is supposed to be a Crown Research Institute but Minister Megan Woods crowed about how she loves spending their profits - so accuracy, accountabilty, those that fund NIWA - all come second we guess. A bit like Russia, China, Cuba...people are second to Government.

But scrappy politics aside, head forecaster Philip Duncan raises a great point about long term forecasting in New Zealand. "How on earth do we get it accurate for 3 months ahead when we still struggle for 3 days ahead?". He says it really all comes down to how you INTERPRET the long range/climate data.

"Our unique focus is to help people before profits - so our forecast, generally, says the North Island looks warmer and drier this summer. But that can't *possibly* be true for every nook and cranny, for every valley and mountain top. So how do we make sense of this? We grab a piece of Swiss cheese of course!".

Swiss cheese - "the cheese with holes in it!".

So apply the long range rainfall map - the whole North Island and eastern half of the South Island leaning drier than normal. Now we add a uniquely NZ recipe - a tropical airflow from near Fiji, a cooler airflow from the Southern Ocean, a large high over the Chatham Islands to our east...and perhaps we start getting those afternoon downpours. They love forming inland - Central Plateau, inland Northland, the Waikato basin, the Canterbury plains, the eastern Otago ranges, the Hawke's Bay and Gisborne ranges. Some classic thunderstorm breeding grounds. Then, because NZ is so narrow, those downpours drift one way or the other in a straight line quite often. 

Scatter a few downpours - throw in a low from the tropics or Southern Ocean we didn't expect - and now our long range 3 month rainfall map has holes in it!

It's important to note that the overall trends and data are a great guide - but the localised daily weather events make for localised changes.

Only admits there are flaws in the forecast data so publicly. China, Russia, Fiji, Cuba, NIWA here in NZ, they all lean towards Government perferction. That the 'people' are wrong and not them - as Government.

The local weather changes that pop in NZ are critical. It's what we love also calling the "wild card effect" as it gives farmers, growers and others in desperate hope of more rain a silver lining to feel positive about when things look depressing, stressful and dire. There is always a silver lining in NZ - no matter how depressed you are about the weather. Please remember that if you're in stress right now. (Also, reach out to us using the Contact Us button if you're in stress or depression due to the weather and climate - we can help).

So remember - can give long range trends with accuracy, especially with IBM's super computer which dominates all NZ Government forecasters (3 of them you tax fund or tax own now!) combined into one place as it's so globally significant.

But - NZ will do what NZ does...we will continue to be unique, think outside the box and challenge authority. In other words - the Swiss Cheese Effect. There may be holes in our long range data - and the more you know and understand why (and the less we try to sell you a 'perfect' nonsense forecast) the more you'll trust what we say and see how Mother Nature works.

We're on your side - we're here to help all hard working Kiwis - we're here for the good of all New Zealanders - and the good you provide in return. - wishing you a wonderful summer ahead. Let us know what more we can do to help you.


Nicely done...!

Been very, very impressed with WeatherWatch for a long time now. You’re leaving the others in your dust...

wishing you a wonderful summer ahead. Let us know what more we c

you can by delivering a decent hot sunny summer thats long.