Extreme weather is shattering records in 2019 - and we're only a few weeks in

Sunday, 3 February 2019

Australians endured hot days at the beach as temperatures hit more than 40C across the Tasman.

It's been less than five weeks since the start of 2019, but this year is already seeing the destruction of weather records worldwide.

New Zealand has just sweltered through record-breaking heat, where both Hamilton and Wellington recorded their highest temperatures ever, at 32.9C and 30.3C.

A slew of records fell during Australia's heatwave.

According to Niwa, temperature records were smashed in numerous towns and cities too, including Upper Hutt (33.5C), Levin (32.6C) and Whakatane (33.3C). Hanmer Forest reached a scorching 38.4C.

While we baked, our neighbours across the ditch did too. January was officially Australia's hottest month on record.

New Zealand felt the heat as well, with temperatures going above 30C in parts of the country.

* Adelaide swelters through hottest day on record

* The science behind why it's so hot**

But it wasn't hot everywhere. The United States had its own record-shattering weather, with a polar vortex plunging temperatures to sub-Antarctic levels.

So what's going on, and what's causing the chaotic weather?

AUSTRALIA'S HEATWAVE

The polar vortex brought much of the USA to a standstill.

Australia sweltered through its hottest month on record in January and the summer of extremes continued with wildfires razing the drought-parched south and flooding in expanses of the tropical north.

Australia's scorching start to 2019 - in which the mean temperature across the country for the first time exceeded 30 degrees Celsius - followed Australia's third-hottest year on record. Only 2005 and 2013 were warmer than 2018, which ended with the hottest December on record.

Chicago froze over as the polar vortex hit.

The South Australian capital Adelaide on January 24 recorded the hottest day ever for a major Australian city - a searing 46.6 C.

On the same day, the South Australian town of Port Augusta, population 15,000, recorded 49.5 C - the highest maximum anywhere in Australia last month.

Climatologist Andrew Watkins described January's heat as unprecedented.

'We saw heatwave conditions affect large parts of the country through most of the month, with records broken for both duration and also individual daily extremes,' Watkins said in a statement.

The main contributor to the heat was a persistent high-pressure system over the Tasman Sea between Australia and New Zealand that blocked cold fronts from reaching southern Australia.

POLAR VORTEX IN THE USA

Millions of people across America's Midwest have endured a deadly deep freeze, with temperatures in parts dropping below -46 degrees Celsius.

In Mount Carroll, Illinois, a trained weather observer reported that temperatures plunged to -39C on Thursday morning (Friday NZT), according to the US National Weather Service.

Temperatures plunged below zero elsewhere in the Midwest, including in Aberdeen, South Dakota, where the mercury dropped to a record-breaking -36C. The city's previous New Year's Day record had stood for 99 years.

In Nebraska, temperatures hit -26C before midnight on Sunday (local time) in Omaha, breaking a record low dating to 1884. Omaha officials cited the forecast in postponing the 18th annual New Year's Eve Fireworks Spectacular that draws around 30,000 people.

The weather service said temperatures in Indianapolis early on Tuesday (Wednesday NZT) tied a record low of -24C for January 2 set in 1887.

The cold killed more than two dozen people, and left hundreds suffering from frostbite.

In Illinois alone, hospitals reported more than 220 cases of frostbite and hypothermia since Tuesday (Wednesday NZT).

Hennepin Healthcare in Minneapolis normally sees around 30 frostbite patients in an entire winter. It admitted 18 in the past week, spokeswoman Christine Hill said.

'I definitely saw more frostbite than I've ever seen in my entire career just in the last three days,' said Dr Andrea Rowland-Fischer, an emergency department physician at Hennepin Healthcare.

WILD WEATHER'S CAUSE

Australia's Climate Council, an independent organisation formed to provide authoritative climate change information to the public, issued a stark warning over the damaging weather.

'Climate change is cranking up the intensity of extreme heat, and January's record-breaking month is part of a sharp, long-term upswing in temperatures driven primarily from the burning of fossil fuels,' the council's acting chief executive Martin Rice said in a statement.

A polar vortex was responsible for the dangerously low temperatures in the USA.

There are not one but two polar vortexes in each hemisphere, North and South. One exists in the lowest layer of the atmosphere, the troposphere, which is where we live and where the weather happens. The other exists in the second-lowest, called the stratosphere, which is a shroud of thin air that gets warmer at higher altitudes.

If the two polar vortexes line up just right, the Lower 48 can find itself in a very deep freeze.

The tropospheric polar vortex is the one that affects our weather. Most of the time, its harsh conditions are out of reach. But every so often, lobes of it pinch off from the main flow and crash south. This can lash the Lower 48 with piercing shots of cold, intense bouts of storminess and bitter wind chills well below zero. How cold it gets in the Lower 48 depends on how much of the vortex breaks off and how far south it gets.

- Stuff and AP