Watch the wind move across New Zealand and the South Pacific — the flowing lines show its direction, the colours show its strength, from the surface up to the jet stream. Drag the timeline to fly up to five days ahead and see weather systems approach long before they arrive.
How this map works
Every flowing line on this map is a virtual particle being carried by the wind exactly as a balloon released at that spot would be. Thousands of them drift across the screen at once, each one continuously reading the wind speed and direction beneath it from a grid of forecast data. Their direction shows you where the air is going, their colour shows you how fast, from deep blue calms through greens and yellows to the reds and magentas of storm-force wind. Underneath the particles, a soft colour wash shows the same speeds as a continuous field, which is what makes a distant storm jump out of the map before you have consciously read a single line.
The four altitude buttons are four different journeys through the atmosphere. Surface is the wind you feel on your face, measured at the standard ten metres above the ground. The 1.5 km view, which meteorologists know as the 850 hectopascal level, sits above the friction and clutter of the land, so fronts and lows show their structure far more cleanly. The 5.5 km view shows the mid-level flow that steers rain bands and thunderstorms. Jet 10 km is the realm of the jet stream, the narrow river of air near cruising altitude that can top 300 kilometres an hour and drives the whole procession of weather systems across the Tasman. Drag the timeline and you fly forward through the forecast up to five days; scroll, pinch or use the buttons to zoom from the whole South Pacific down to your own stretch of coast.
How wind forms
All wind begins with the sun. The Earth is heated unevenly, strongly at the equator and weakly at the poles, and the atmosphere spends its entire existence trying to smooth that difference out. Where air warms it expands and rises, leaving slightly less air at the surface, which we measure as low pressure. Where air cools and sinks it piles up, and we measure high pressure. Air then flows from high to low, the way water runs downhill, and that flow is wind. The bigger the pressure difference over a given distance, the harder the air is pushed, which is why the tightly packed isobars on a weather chart mean a rough day and widely spaced ones mean you can hear the birds again.
If the Earth stood still, wind would blow in a straight line from high to low pressure and weather would be dull. Because the planet rotates, every parcel of moving air is deflected sideways, an effect called the Coriolis force. In the Southern Hemisphere the deflection is to the left, which is why our air spirals clockwise around low pressure systems and anticlockwise around highs, the mirror image of the Northern Hemisphere. It also gives us a trick sailors have used for generations, a Southern Hemisphere version of Buys Ballot’s law: stand with your back to the wind and the low pressure lies on your right. Close to the ground, friction from hills, forests and waves slows the wind and drags it slightly across the isobars toward the low, which is one reason the surface view on this map often looks calmer and more tangled than the smooth rivers of air at 1.5 km.
Why New Zealand is one of the windiest countries on Earth
New Zealand sits between roughly 34 and 47 degrees south, squarely inside the belt of westerlies that sailors named the Roaring Forties. Down here there is almost no land to slow the wind, just an unbroken ring of Southern Ocean, so the westerlies arrive at our coast with thousands of kilometres of open-water run-up. We are two narrow, mountainous islands standing directly across that flow, which is roughly what happens when you build a fence across a river.
The mountains cannot stop the air, so the air finds the gaps, and the greatest gap of all is Cook Strait. When wind is squeezed between the ranges of the lower North Island and the Kaikōura coast it accelerates sharply, the same physics that makes water speed up through the narrow neck of a hose. That funnelling is why Wellington regularly ranks among the windiest cities in the world, averaging around 170 days a year with gusts above 60 kilometres an hour, and why the strongest winds in the country so often turn up on the capital’s south coast. Watch the map during any decent southerly or northerly and you can see the strait light up in yellow and orange while regions either side sit quietly in green.
The winds New Zealanders know by name
The nor’wester is Canterbury’s famous hot wind, and it is a textbook föhn. Moist westerly air is forced up and over the Southern Alps, dumping its rain on the West Coast, which is how Milford Sound ends up with around seven metres of rain a year. Having wrung itself out, the air descends the eastern slopes, and dry air warms faster on descent than moist air cools on ascent, so it arrives on the plains hot, dry and gusty, often under the long smooth band of cloud Cantabrians call the nor’west arch. On this map a nor’wester shows as a hard river of orange pouring across the South Island while the West Coast sits under the heaviest rain in the country.
The southerly change is the other half of the same story. Cold fronts sweeping up from the Southern Ocean run north along the east coast, and the temperature can fall ten degrees in half an hour as the wind swings violently from northwest to south. The most infamous southerly in the country’s history arrived in April 1968, when the remains of tropical Cyclone Giselle collided with a cold southerly over Cook Strait. Gusts around 235 kilometres an hour were recorded on Wellington’s south coast before instruments failed, and the interisland ferry Wahine foundered at the harbour entrance with the loss of more than fifty lives. It remains the benchmark against which every Wellington storm is measured, and it is exactly the kind of collision this map is built to let you watch forming days ahead.
How the GFS weather model works
The winds on this map come from the Global Forecast System, or GFS, a numerical weather model run by NOAA, the United States weather agency, and made freely available to the world. Four times a day, at midnight, 6am, midday and 6pm UTC, the model ingests millions of fresh observations, from satellites, weather balloons, aircraft, ships and surface stations, and uses them to build its best estimate of the state of the entire atmosphere at that moment. That starting snapshot is called the analysis, and it is the “now” frame on this map.
From there, the model does something remarkable. It divides the atmosphere into a three-dimensional grid, cells about 13 kilometres across stacked in 127 layers from the surface to the edge of space, and then solves the fundamental equations of fluid motion and thermodynamics for every cell, stepping forward a few minutes at a time, out to sixteen days. Nothing about it is guesswork or pattern matching against past weather. It is physics, computed by one of the larger supercomputing systems on Earth, and the forecast you scrub through here is the direct output of those equations, published on a quarter-degree grid and refreshed with every model run. Our collector fetches the New Zealand and South Pacific window of each run, from the surface up to jet level, within hours of it being published.
GFS is one of a handful of global models that forecasters compare constantly, alongside the European Centre’s ECMWF model, which often edges it in headline accuracy scores, and regional models that MetService runs at finer scales over New Zealand itself. Each has strengths, and when the big models agree, confidence is high. When they disagree, that disagreement is itself the forecast: it tells you the atmosphere is finely balanced and the details are still up for grabs.
Tropical cyclones and how they reach New Zealand
Tropical cyclones are born in the warm seas at the top of this map, in the Coral Sea and the waters around Vanuatu, Fiji and Tonga, mostly between November and April. They need sea surface temperatures above about 26.5 degrees to fuel them, and they need to be far enough from the equator, roughly five degrees of latitude or more, for the Coriolis effect to set them spinning. Warm moist air spirals inward and upward, condensation releases heat, the heat drives more rising air, and a self-feeding engine forms around a calm central eye. On the wind map a cyclone is unmistakable, a tight, brilliantly coloured spiral in the tropics, often visible in the forecast days before it has even been named.
Most cyclones that head our way weaken over cooler water and are reclassified as ex-tropical, but that prefix is dangerously misleading. As they transition they trade their compact fury for sheer size, spreading damaging wind and rain over a far wider area, and some re-intensify as they merge with fronts in the Tasman. Cyclone Bola in 1988 dropped more than 900 millimetres of rain on parts of the East Coast in three days after it had officially stopped being tropical. Cyclone Gabrielle in February 2023 was also ex-tropical by landfall and became the country’s deadliest storm this century. The lesson, every time, is to watch the system, not the label, and the five-day scrub on this map is the simplest way to do that. When a cyclone is active in our coverage area, our cyclone tracker carries a live page for that storm, built from this map and the satellite view, and keeps a permanent replay of every storm afterwards. For the photographic view of the same storm, our live satellite map shows the actual cloud spinning where the model says the wind is.
The jet stream above New Zealand
Ten kilometres overhead, where airliners cruise, the westerlies concentrate into jet streams, ribbons of wind a few hundred kilometres wide that regularly exceed 200 kilometres an hour and can go well beyond that in winter. Switch this map to Jet 10 km and you will usually find one arcing somewhere across the Tasman. The jet matters for two very practical reasons. It is the steering current for surface weather, so lows tend to form beneath its meanders and travel along it like leaves in a stream, which means today’s jet pattern is a preview of the week’s weather. And it is why your flight home from Sydney is noticeably quicker than the flight over: eastbound aircraft ride it, westbound aircraft fight it.
Reading a wind forecast wisely
A useful rule of thumb is that the broad shape of the forecast, where the highs and lows will be, is usually trustworthy several days out, while the fine detail, the exact gust at your beach at 3pm, only firms up inside a day or two. Chaos theory was, famously, discovered by a meteorologist: tiny uncertainties in today’s observations grow into large differences a week out, and no computer will ever fully escape that. So use the five-day view for the story, where the systems are and where they are heading, and treat the last click of detail as guidance. The model run and its update time are always shown in the corner of the map, so you know exactly how fresh what you are seeing is.
And a note worth repeating whenever the map turns red: this is an information tool, not a warning service. Official watches and warnings for New Zealand come from MetService, and emergency instructions come from NEMA and your local Civil Defence group. When they say move, move; this map is for understanding why.
Explore more live data
See the same sky from space on the NZ satellite map, follow every tropical storm on the cyclone tracker, watch how much of the country’s electricity the wind is generating right now on NZ Grid Live, check what’s happening across the country, or look up today’s tides and tonight’s aurora chances.