Historic polar outbreak invades South America's "cone"

The worst winter weather in several generations pushed up into South America last weekend and early this week bringing life-threatening temperatures and widespread low-level snow. It was remarkable for its intensity, especially at low elevations, and its geographic spread as it covered seven southern countries in the continent, locally known as "the cone".

The polar outbreak brought snow to Santiago in Chile, down to sea level not far from Buenos Aires, Argentina, and deep snow along the Andes. The polar wave dropped temperatures by over 20° in a matter of hours, and pushed as far north as Peru, Paraguay, Uruguay and southern Brazil. Temperatures kept dropping to break records at some long-standing stations by large amounts.

Snow fell in Santigo in Chile (500m elevation) on Saturday 15 July, killing one person, injuring two and leaving 250,000 without power. Seventeen centimetres of snow accumulated in the city which, at 33.5°S, is the same distance from the equator as Sydney. Up to 40cm was reported in some eastern suburbs surpassing depths reached in the exceptional storm of 1971. The view across the city to the Andes later on Saturday, after the snow melted in the city and the cloud cleared, was spectacular. Airports, numerous main highways south of Santiago and mountain passes were closed, and the storm even forced suspension of the football matches of the Chile Cup.

Conditions were more serious in Argentina where at least four deaths were caused by the cold, which reached a record -25.4° at the ski resort town of Bariloche on 16 July. The previous record of -21° was set in 1963 [Argentina-Servicio Meteorologico Nacional† and TASS†]. Fresh powder snow in the Andes was up to waist level. Snow even fell in the city of Rosario (31m), on the Paraná River 280km upstream of Buenos Aires.

The polar outbreak moved north into Uruguay, Paraguay, southern Brazil, Peru and Bolivia early this week (17-19 July). In the Peru/Chile/Bolivia border area it brought minimum temperatures in the -10 to -15° range. In Bolivia, gale-force winds compounded the discomfort in some areas while the government closed many schools between 17 and 19 July. In Uruguay, unaccustomed to such cold conditions, the government issued advice† to the population on how to keep houses warm, and how to avoid, recognise and treat hypothermia. Temperatures in the country dropped as low as -10°.

This is one of a succession of severe cold changes to sweep through South America, with life for those on the land so dire on the Bolivian Altiplano and higher parts of Peru, Chile and Argentina that their governments are distributing aid throughout the region. Snow has been only one of the problems. It has been accompanied by high winds, very cold temperatures and frosts that have put livestock at risk and ruined subsistence crops that many people on the land rely on.

Australian weather briefs

Heavy snow stopped falling and the sun, and visitors, came out at Cradle Mountain early this afternoon. Snow at the car park level was officially measured at 15cm deep. TAS Parks & Wildlife Service

• An active cold front pushed through TAS this morning bringing the heaviest snow so far this winter to highland areas and falling as low as 400m. You can see the snow accumulating rapidly between 09.00 and 12.00 EST (23.00 to 02.00 UTC) in this Himawari satellite animation*. On the Central Plateau, the Great Lake Hotel offered its guests more picture postcard opportunities.
• The front also brought boisterous winds around Bass Strait as it moved through with both Wilsons Promontory VIC and nearby Hogan Island reporting gusts to 128km/h. In far NW TAS, Cape Grim reported 115km/h.
• More good snow fell across the skiing resorts overnight and this morning, with Snowy Hydro's weekly reading at Spencer's Creek, mid-way between Perisher Valley and Charlotte Pass showing 88cm this morning, an increase of 29cm in the past week and 84cm in the past three weeks. There was also a good cover of snow around Lake Jindabyne this morning at an elevation of 920m.
• Farther north in QLD and the NT, the strong temperature gradient between the cold weather down south and the consistent warmth of the tropics has strengthened the trade winds, bringing out strong wind warnings in the Gulf of Carpentaria and setting new records for high daily average wind speeds. Today it was the turn of Brisbane Airport, its average wind speed over the full 24 hours to 09.00 being 28.8km/h, the highest in 14 years.

 Still plain sailing with climatic indicators

The main climatic influences that effect the longer-term forecast of Australian weather show little change, itself a sign of the current stability.

The El Niño-Southern Oscillation (ENSO), which determines our likelihood of moving into El Niño or La Niña conditions, remains neutral with all models surveyed by the BoM indicating it will stay that way for the remainder of 2017. This is despite central tropical Pacific sea surface temperatures 0.5° above normal. However, this area of warmer water is a localised warm anomaly, and the overall temperature pattern is inconsistent with development of an El Niño.

The Indian Ocean Dipole also remains neutral with only one of the six models surveyed forecasting it will go positive for long enough to reduce winter and spring rainfall across southern and central Australia. On balance, the BoM believes it will remain in a neutral state.

The Madden-Julian Oscillation (MJO) reappeared over the Indian Ocean last week, stimulating heavy rain in India from the Southwest Monsoon and the development of tropical storm Talas, which brought flooding rain to parts of SE Asia. However, most models suggest the MJO will persist over the Indian Ocean at relatively weak levels although some are indicating a marginal strengthening. The MJO has little effect on northern Australia during the winter months.

Full details can be found in the Bureau's ENSO Wrap-Up and Weekly Tropical Note, issued yesterday.

 Cold with rain and snow in the SE while hot in other parts

A series of cold fronts and troughs has moved over SE Australia during the past two days, bringing a few heavy falls of rain, good snow to the VIC and NSW Alps and also light snow to lower levels northwards up the NSW ranges. QLD, the NT and WA were unusually warm for July.

An area around Adelaide's Mt Lofty has had two days of heavy rain on 17 to 19 July. To 09.00 yesterday morning (18 July), Bridgewater, Lobethal, Hahndorf and Balhannah all had between 48 and 54mm in the gauge with some new records for newer stations. To 09.00 this morning, Mt Lofty itself recorded 40mm and a number of gauges in the area reported only a little less. In the Barossa Valley, Greenock and Nuriootpa had their wettest July day in over 15 years with 31.0 and 30.8mm.

Tasmania has also seen some good falls as a complex trio of low pressure systems moved under and over the island and through Bass Strait. The heaviest were in the north, but the most remarkable was 13.0mm in Hobart to 09.00 today, the city's heaviest one-day total in six months.

Cold air moved into VIC and southern NSW yesterday and today, bringing 15 to 30cm of snow to the resorts. The cold air continued north today, with cloud keeping top temperatures very low up the NSW Divide and reports of light snow at Shooters Hill S of Oberon, Yetholme and Sunny Corner between Lithgow and Bathurst, Barrington Tops 100km N of Newcastle, and around Guyra on the Northern Tablelands.

Meanwhile, in an arc around the northern half of the country, the days have been unusually warm. In WA, Perth had its equal sixth warmest July day since record-keeping began 120 years ago with a top of 25.0° yesterday - the last time it was this warm in July was in 1999. Records for high July maximum temperatures were set across WA, the NT, QLD and even into northern NSW Yesterday (Tuesday) and today ahead of the colder change in the east.

 Heavy winter weather batters New Zealand's North Island

Here is the view of New Zealand from NASA's Terra satellite at 12.00 NZST, Thursday 13 July. The image uses three of the satellite's bands (3-6-7) to highlight lying snow (bright red) and high cloud composed of ice crystals (reddish-orange grading through to peach colour). Lower cloud made up of liquid water shows up as a white or off-white colour while vegetation is green. The extent of the snow across the South Island can be seen, while in the North Island thick, high cloud with ice crystal tops is spiralling into the low located in Hawke's Bay, NE of Napier. NASA Worldview

Continuing the AWN story on 13 July, Thursday 13 July began with MetService warnings and watches for snow, heavy rain and gales covering a large part of the country.

The low over the North Island continued to feed a stream of rain, sleet and snow across the east and the northern high country of the South Island, but this eased, at least at lower levels, as the morning progressed and sun broke through in places revealing a snow-covered countryside. The ski resort village at Mt Lyford in the Kaikoura high country 130km NE of Christchurch reported 60-70cm new snow on the ground.

Thursday and the first half of Friday were appalling days across the southern, central and eastern North Island, with the worst of the weather slowly contracting north with the low pressure system. Hurricane-force winds and heavy rain with flooding battered the south, while snow up to half a metre deep piled up from the centre of the island east to the Hawke's Bay area.

• Overnight into Thursday, conditions in Cook Strait were atrocious, with average wind speeds of 130km/h during the morning with 11m waves. Inter-island ferries remained suspended.
• Wellington was battered by wind gusting as high as 160km/h on Mt Kaukau, just north of the city, and 167km/h at Baring Head, east of the entrance to Wellington Harbour, according to Metservice.
• Tom Adams from Metservice, speaking early on Friday morning, said that in the Wellington area it had "calmed down" at the airport and in the hills "just to 110km/h gusts" with some stations reporting 190mm of rain in the past 24 hours.

• The wind in the lower North Island caused widespread damage, with trees downed and some roofing iron blown off. Wind and the weight of heavy snow brought down powerlines causing 10,000 blackouts.
• Flooding in the Wairarapa area NE of Wellington caused town inundations and some evacuations. Numerous substantial land slips as well as fallen trees blocked roads in the southern half of the North Island.
• In the centre of North Island, snow fell as far north as Rotorua. Half a metre of snow with blizzard conditions were reported overnight into Friday at Turoa ski area at 1,600m, on the SW side of Mt Ruapehu. East of there, the towns of Raetihi and Ohakune were cut off by snow said to be the heaviest in more than 20 years.

The Desert Road at its summit in central North Island. The chain of Mt Ruapehu's volcanic mountains catches the rising sun on the left on Sunday 16 July. NZ Transport Agency

RNZ provided extensive coverage, giving detailed reports late on the Thursday, and again on Friday afternoon as the weather began returning to some normality. This report details the unusually heavy snow in the North Island. These were in addition to nearly continuous chatty radio and TV reports such as this in the thick of the bad weather in the North Island on Thursday afternoon.

New Zealand only has a short while to draw breath, with a further bout of wind, rain and snow, falling as low as 400m in the South Island, due to move in from Thursday 20 to Saturday 22 July.

[RNZ, Canterbury Weather Updates, Metservice, NZ Civil Defence, NIWA]

 Extreme winter weather grips New Zealand

Both islands of New Zealand have been experiencing wild winter weather, with snow falling to sea level isolating towns and closing roads, flooding leading to evacuations, winds to 160km/h around Wellington and waves to 11m making Cook Strait live up to its reputation.

In the first real taste of winter, freezing weather and substantial snowfalls pushed north up the South Island on Tuesday in the wake of an active cold front. Air behind the front was exceptionally cold, not just at the surface but in the upper atmosphere as well, resulting in a deep upper cold pool with a temperature down to -38° at 500hPa (about 5.5km). This cold pool generated a deep low off the east coast of the North Island yesterday, prolonging the stream of low-level snow and cold air into the South Island today and bringing gales, heavy rain and snow down to as low as 200m as it crossed the North Island.

On Wednesday:

• Heavy snow fell down to 100m with light snow to sea level in Christchurch overnight, and snow and icy roads in and around Dunedin today. Heavier falls closed roads across the east and south of the South Island above 200m as well as the passes. Contractors were gritting and ploughing roads in an effort to keep traffic moving.
• Sheep and beef farmers were battling settling snow ranging from 15cm at 200m to over 40cm at higher elevations.
• Gales and high seas in Cook Strait gave some very rough crossings before the deteriorating weather led to cancellation of inter-island ferries as well as many air services between the two island.
• Bitter cold pushed the country's spot electricity prices through the roof with average prices eight times higher than on Tuesday.
• Social media was almost in melt down as pictures, videos and stories were exchanged. Here's a gallery of photos that gives a feel for the day.
• By day's end, the most severe weather was pushing into the North Island.

[Radio New Zealand, MetService, Canterbury Weather Updates]

Australian weather briefs

• Strong high brings cold nights...and wind. Strong high pressure just east of TAS and a ridge from it into QLD brought with it clear skies, light winds and dry air descending from upper levels to give TAS, VIC, NSW and southern QLD another cold night. According to Ben Domensino at Weatherwatch, Saint George QLD with -0.1°, Perisher Valley NSW (-11.6), Mount Hotham VIC (-8.2) and Wynyard and Dennes Point TAS with -2.3 and +2.0 each had their lowest minima in two years. Orange Airport NSW has now had three consecutive nights below -4° with minima of -4.4°, -4.3 and this morning -4.8. The strong high has been tightening the pressure gradient across northern Australia, freshening the southeasterly trade winds. Coen, Weipa and Horn Island, all on Cape York Peninsula, all set new records for highest average 24-hour wind for July to 09.00 this morning.
• Good to see someone with a dry sense of humour on the BoM's Twitter desk at the Tasmanian office this afternoon. Although it wasn't appreciated...

World weather briefs

• Tropical Cyclone Nanmadol brings death and devastation to southern Japan. TC Nanmadol, which formed in the Philippines Sea on 2 July, made landfall in Japan at 09.00 local time on 4 June about 40km E of Nagasaki, Kyushu Island. Continuous very heavy rain continued to fall in parts of SW Japan into 6 July, with parts of Fukuoka Prefecture, at the north of Kyushu, receiving up to 600mm in the 48 hours to 10.40 on 7 July, 1.6 times the rain that normally falls during the whole month of July. Some of the rain was phenomenal, Asakura, in the hills in southern Fukuoka, recording about 500mm in nine hours between 12.00 and 21.00 on 5 July with 106mm of that falling in just one hour to 17.00.
  
  Fukuoka and neighbouring Oita prefectures bore the brunt of the resulting floods and mudslides in Kyushu, Japan's southernmost main island. As at 10 July, local media reported a death toll of 18 with 30 people missing and over 440,000 evacuated. More details of the event are on Floodlist. Widescale destruction was reported, as these articles from Associated Press, Thomson Reuters Foundation and Al Jazeera show.
• Assam plagued by long-term flooding. Assam in far NE India has experienced severe weather, storms, strong winds and heavy rain since early May, causing flooding and waterlogging main river catchments. Flooding worsened on 2 July when heavy monsoon rain caused the Brahmaputra River and tributaries to rise, submerging new areas. Official figures at 5 July showed 390,000 people were affected in over 850 villages across nearly half the 32 districts in Assam. Over 500 villages are under water and relief centres have filled rapidly, housing 45,000 people at 5 July. A 2 July report from the Assam Disaster Management Authority, with map, is here, and Floodlist's report is here.

Widespread flooding, landslides in southern and central China

Heavy rain and the flooding and landslides triggered by it have caused catastrophic losses in southern China from about 20 June to the first week of July. The rain continued a sequence of rain and hail storms that started in May.

The most notable event was a massive landslide in Xinmo village, Sichuan province, 1750km W of Shanghai, on 24 June which killed at least 15 people and left nearly 100 missing [Al Jazeera]. Farther afield, Xinhua News Agency reported on 7 July that in the Guangxi Zhuang Autonomous Region, which borders the north of Vietnam, 20 were dead, 14 missing, around 20,000 houses had collapsed or were damaged, and over 92,000 residents relocated.

Farther north, heavy downpours have hit parts of the Yangtze River basin, and are worst in Hunan province, 900km SW of Shanghai. As at 7 July, Xinhua reported 44 people had died or were missing around Changsha, the provincial capital and a city of over 7 million. There, the Xiangjian River, the Yangtze's second largest tributary by water runoff, reached a record 39.51m on 3 July beating the previous record of 39.18m set by a massive flood in 1998. The Xiangjian joins the Yangtze just downstream of Changsha. Changsha recorded 522.4mm over the 9 days to 1 July, more than its average for the three wettest wet season months of April to June. 292mm of that fell in two days 30 June and 1 July alone.

Changsha's local flood prevention headquarters described the flood as the worst natural disaster in the area in 60 years. In Hunan's Ningxiang County to the west of Changsha, about 815,000 people, some 56% of the county's population, have suffered property losses in the floods, it said. Elsewhere in the Yangtze basin, tens of thousands are battling flooding, with the Chinese government setting aside 1.88 billion yuan ($A363 million) for disaster relief in 20 provinces and regions as at 3 July.

Western media reporting of the catastrophic floods included this item from Associated Press suggesting insufficient warning of the flood was given and that, after the flood, the emergency response was slow. Al Jazeera said that over sixty rivers flooded causing 1.2 million evacuations, 38,000 house collapses and damage to nearly 880,000ha (8,800sq km) of crops. Ten major and 89 smaller tributaries of the Yangtze had risen to record levels. Reuters gave details on the effects of the flooding on Chinese and global markets. ABC News described (with video) a particularly harrowing rescue of a man trapped in rapidly rising floodwaters in Yangshuo County, which is in the badly flooded southern Guangxi Zhuang Autonomous Region and 470km NW of Hong Kong.

A report from Hong Kong Red Cross on 9 July, quoting figures from the Chinese Ministry of Civil Affairs as at 7 July, gave the following details: number of people affected 11.08 million, deaths 56, missing 22, evacuated 168,800, collapsed houses 27,000, economic loss Yuan RMB 25.27 billion ($A4.88 billion) and the most affected provinces Zhejiang, Auhui, Jiangxi, Hubei, Hunan, Guangdong, Guangxi, Chongqing, Sichuan, Guizhou, Yunnan.

Australian weather briefs

• Warm in northern Australia: While southern Australia has continued cold the past few days, the north has been positively tropical with record-breaking warm nights and more rain than you'd expect in the dry season. Friday morning 7 July saw a scattering of new high minimum temperature records set in a line from the Kimberley to the Wide Bay area in QLD as warm, humid air was pulled south in a pair of troughs, bringing cloud and rain. Victoria River Downs in northwestern NT had its warmest July night in 50 years with a low of 24.2° and other records are here.
• Automatic weather station fills vital gap: A new, or rather a replacement, automatic weather station has entered service on the Eyre Peninsula, SA. Located at Point Avoid, 48km W of Port Lincoln in the Coffin Bay National Park, the station replaces one 35km to the north at Coles Point which had been operating since 1991. Fishermen leaving the sheltered waters of Port Lincoln, in particular, will welcome the return of observations from the exposed west coast of the peninsula.

 Winter arrives in southern Australia...at last!
Updated 9/7/17: new third paragraph, Giles temperature record added at end of story

Winter has arrived with a bang across all of southern Australia during the past week bringing record-breaking cold nights, snow to TAS and WA and the long-awaited substantial falls across the Australian Alps.

Freezing weather began last weekend, 1 and 2 July, when a strong high planted itself over NSW, VIC and TAS giving a string of exceptionally cold nights that set new low July temperature records in the three states. In many cases, the temperatures were all-time lows as well as being July records, and in ten cases records were broken on one night only to be broken again the next night. The provisional records, still subject to confirmation, are given in the Daily Weather Summaries for Saturday 1 July, Sunday 2 July and Monday 3 July.

Very dry air away from the coast helped the temperatures to plummet with many locations reporting dew points below -10°. The dew point is the temperature to which the air must be cooled to reach 100% humidity, at which point dew or frost are formed, a process that releases heat and slows the normal night time temperature fall considerably. When the air is dry and the dew point very low, the temperature can continue to plunge unhindered by this slowing mechanism.

Notable records included Rutherglen VIC, with a 99-year history of minimum temperature reports, which set a July record low of -6.9° on Saturday only to make a repeat performance with the same figure on Sunday. Also in VIC, East Sale Airport set a new all-time minimum in a 72-year history on Monday, its reading of -6.6° knocking 0.8° off the former record set in 1976. Records were broken well into western NSW with Broken Hill (-2.9°) and Wilcannia (-3.1°) setting new all-time lows on Saturday. Wilcannia then made it a double-breaker, with -3.7° the next night.

The coldest temperature over the three nights was -10.4° at Liawenee on the frigid Central Plateau in TAS on 3 July. No cigar for this temperature though, as the station's record is -12.2° set in 2013. Other low minima for each state are given on the State Extremes pages for Saturday, Sunday and Monday. The run of lows in Canberra of -8.7°, -8.2° and -7.1° across the three days shows why parliament doesn't sit at this time of the year.

Special mention must be made of Goulburn, where there is some confusion over the only other double-digit negative minimum recorded during the period. The airport there had three bitterly cold nights in succession from 1 to 3 July: -9.7°, -10.0 and -9.4°. These stood out because they were the equal coldest, coldest and second coldest nationally for each morning. The -10.0° on Sunday 1 July is the figure in contention. It is currently in the official database as -10.0, but the Bureau itself reported the minimum as -10.4° on Sunday morning, raising some question as to what it actually was.

This was the view from the balcony of South Perisher Club Lodge over the valley of Rock Creek at 15.00 today. This snow cam is rare among those in the Alps in that it is not run by ski centre managements, and does not show optimistic views of ski runs where much of the snow can be man-made. Until Monday, this view was of alpine meadow, snow gums and rocks. South Perisher Lodge

The first true snow of winter arrived in the Alps on Monday 3 July with good falls across all resorts, but it was not until Wednesday that heavy snow began. By mid-morning, this video from Perisher Mid Station made it very clear the snow had arrived. Snow depth at Spencers Creek, between Perisher Valley and Charlotte Pass in the NSW Snowy Mountains, shot up from 4cm on 29 June to 43cm a week later, way ahead of the depth at the same time last year, but still below the long-term average of around 80cm at this time in the season. Depths at other skiing centres were similar, and have continued to increase slowly with further snow and sub-zero temperatures. By Friday, even the relatively low Mt Buffalo was accumulating snow.

There were some notable snowfalls away from the Alps. In WA, Bluff Knoll, the highest point in the Stirling Ranges, 75km NE of Albany and 1,099m above sea level, is one of the few places in the state to experience some snow each winter. This week it excelled itself as successive fronts brought two snowfalls in the one week. The first was on Sunday 2 June, setting many locals on pre-dawn treks up to the summit. They were rewarded with what locals told ABC News was the heaviest fall in years. By Wednesday 5 June, when a second wave of cold air was due in the afternoon, the word had obviously got around as a cavalcade of snow-lovers arrived from all over the place, booking out the local accommodation and again trekking up the mountain in the pre-dawn dark. Word from farther west was that the air was indeed cold - Dwellingup, in the ranges SSE of Perth, had a maximum temperature of just 8.8°, its coldest day in 42 years. Unfortunately, those on the Bluff were mostly rewarded with chilling cold and biting wind, but light snow did fall late in the afternoon although, from photos, significantly less than on Sunday. The diehards who waited into the night may have been rewarded with heavier falls.

Tasmanians are much more accustomed to winter snow, with a good polar blast purging the state of its unseasonable warmth overnight 29/30 June. Snow fell down to 300m, including above Kingston and on the eastern ridges of kunanyi/Mt Wellington. Higher parts of the Huon Valley as well as Vinces Saddle, on the main Southern Outlet between Hobart and Kingston, were coated with snow, and black ice on roads was partly responsible for at least one death. On the Central Plateau, blizzard-like conditions prevailed, and at Cradle Mountain young wildlife experiencing its first snowfall had visitors reaching for cameras to capture the cuteness, like this Tassie devil and this wombat. ABC News gives a good coverage.

The cold air through the week didn't move as far north as the tropics, but it did get to Brisbane by Friday 7 July when a cloudy, showery day gave a top of 16.4°, the lowest July maximum since 2010 and the lowest for any month since 2013. On the same day, a combination of cold lower-level air and high pressure gave Yulara a minimum temperature of -3.5°, just 0.1° shy of the Rock's record low in 30 years of recording. Over the border in WA the next day, 8 July, Giles weather station recorded a minimum of -2.5, its all-time lowest temperature on record in 61 years of observations.