http://www.stuff.co.nz/stuff/dominionpo ... a6479.html
(Text and video)
If you google "data rolls in like a hurricane" (the title of the article) the second link will be to press viewer- this one has the pictures.
As a fierce Wellington northerly buffets MetService's hilltop base in Kelburn, a bell tingles in the forecasting room inside.
View video: How MetService makes the weather
It's 9.45am on Thursday, and 10 forecasters gather to discuss a mix of wind and rain set to lash New Zealand for the next 48 hours.
The forecasters' shift started at 5.45am, and today there's a serious air in the room as they pull a mass of data into a clear picture of the weather. Conditions are especially nasty, as the glowering sky avows.
"It's a bit like the flight deck on an aircraft," says national forecasting centre manager Peter Kreft. Certainly the view is similar, a peerless outlook across the harbour and south to Island Bay and Cook Strait.
Below, the ferry Kaitaki has pulled out into a dark and mean-looking Wellington Harbour.
As any farmer will tell you, the weather is serious stuff. Accurate forecasting can save lives.
The marine forecasting unit's data came into play last week when Itintarawa Baraniko and Baraniko Tebeau were spotted floating 26 kilometres off the Napier coast in a tiny dinghy, after a fishing trip went awry. Estimates of wind strength were used to pinpoint where the pair should have drifted to.
The prediction proved spot-on.
On April 15, the weather's malevolence was underlined by the Mangatepopo canyoning tragedy, which killed six pupils and a teacher from Auckland's Elim Christian College. They died after torrential rain in the river's catchment raised the river's flow from 0.5 cubic metres to 18 cubic metres per second in half an hour.
Two MetService alerts - a heavy rain warning and a severe thunderstorm watch - had been issued but the Edmund Hillary Outdoor Pursuits Centre said it did not get them.
As the meeting proceeds, meteorologist Mads Naeraa explains that snow is expected almost to sea level in Southland, Otago, and Canterbury. Two fronts crossing the country bring cold, wet, windy weather everywhere.
A severe weather warning has been issued, with heavy rain expected on the West Coast, and gales in Wellington and parts of Wairarapa. Meteorologists speak in turn as they work out a coherent picture to underpin all forecasting today. Outside, it's a bracing 9 degrees celsius, with winds gusting to more than 100kmh.
So where do forecasters get all this information? The map is drawn from thousands of measurements streaming in from rain radars, weather stations and satellite images. Seventy-one weather stations around New Zealand report every minute on wind, temperature, humidity and rain.
Some merchant ships are also equipped with weather instruments, supplied by MetService, turning them into mobile weather stations. Drifting weather buoys add to the picture.
Five rain radars cover the country from Warkworth, New Plymouth, Wellington's south coast, Rakaia on the Canterbury Plains, and Invercargill airport. "Part of a forecaster's job is to make sense of situations where they'll usually have far more information than they need," Mr Kreft says.
Satellite pictures come from MTSAT-1R, launched by the Japan Meteorological Agency in 2005. It sits 35,790 kilometres above Earth.
At that height, the satellite orbits Earth at the same rate that Earth rotates underneath it, meaning it is parked in orbit above the Pacific.
MTSAT-1R is 33 metres long with its solar panels outstretched, and weighs 1.76 tonnes.
Its data feeds to a dish on the roof of the MetService building, tethered against the wind by a criss-cross of steel trusses.
The forecasting room is divided into sections dealing with regional forecasting, marine, severe weather, and aviation.
In the aviation section, forecaster Matthew Ford taps away at the forecast for Christchurch airport. Unlike forecasts for public consumption, it's a stark block of data and codes, unfathomable to the untrained eye.
Pilots are not worried if their washing will get wet, they want to know about turbulence, visibility, and how low clouds will be.
Altimeters have to be re-calibrated according to barometric pressure. "That's so they don't fly their plane into the ground," Mr Ford says.
Each forecast is peer-reviewed before being issued. The forecasting room works 24/7 with a revolving cast of 45. It's a mini United Nations, including a Dane, a Fijian, and an Icelander.
Meteorologist Steve Ready says the service does not advise anyone on what they should and should not do according to the weather.
"Our customers have to make decisions based on the information we give them."
Mr Kreft says that despite the torrents of data coming in, forecasting is still very much a human endeavour. "There's an interesting mix of the human and the machine.
"Computers have revolutionised weather forecasting over the past few decades and can do mathematics that humans couldn't possibly achieve in any reasonable time.
"On the other hand, humans can reconcile computer guidance with observations.
"Humans are absolutely fundamental to weather forecasting and I don't think that will ever change."
