Reviews of weather events and climate news are normally written some days after the fact to give time for accurate information to become available, and as I have the time to research and write it. If you're looking for weather news as it breaks, I've listed reliable, organised sources on AWN's Weather and Climate Media Reports page.
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More to come after July gives Australia record hot days
The average maximum temperature across the country as a whole last month was the highest since reliable records began in 1910, the BoM reported today. At 2.62° above average, it resoundingly beat the former record of 1.96 above the norm set in 1975.
QLD, WA and the NT all experienced their hottest daytime averages for July since records began 108 years ago, with QLD's 3.03° above normal breaking a record that has stood since 1915. NSW had its second-hottest July days on record, SA its third-hottest and VIC its sixth-hottest. Only TAS bucked the trend with regular cool to cold westerly changes keeping daytime temperatures to 0.11° below average.
Dominant high pressure over the southern half of the continent produced generally calm weather, allowing days to heat up and night-time temperatures to drop, especially in southeastern states. NSW, VIC and TAS all showed below average minimum temperatures, with NSW having its coldest July nights since 2002. The west and north, however, had above average nights with QLD posting its tenth highest July average minimum and the NT their seventh highest.
Rainfall in July was again well below average. A broad band of the continent running from the W and NW coasts of WA through to coastal NSW and eastern VIC had less than 40%, and in many places less than 20% their normal July rain as the persistent high pressure kept the westerlies and cold fronts that normally bring winter rains to southern Australia well to the south. The rainfall deficiency "drought" map for the three months May to July show most of western WA, southern SA, central NSW and the eastern half of VIC with severe deficiencies, and large areas in bright red indicating their lowest rainfall on record for those three months.
Both the increasingly warm daytime temperatures and the southern movement of winter rain away from important cropping areas are consistent with climate warming. BoM meteorologist Greg Browning told ABC News it was "basically this background warming signal that we're seeing right across the globe associated with global warming. It seems like the warming conditions we've seen right across the globe are just becoming commonplace, and we're seeing them in monthly temperatures on a regular basis."
The Bureau's Climate Outlook for August to October offers little change from the warm, dry conditions in the west and south with the main difference being warmer nights. While rainfall across the three months should be closer to normal in TAS, QLD, and the northern NT, daytime temperatures in August are given the unusually high 80% chance of being above normal across most of the country, so prepare for some pre-spring heat. The latest full Climate Outlook, where you can click on the maps to get detailed information for your area, together with the outlook video are here.
Australian weather briefs
- A large area of heat has been slowly making its way across Australia, drawn down from the tropical north by passing cold fronts in the Southern Ocean. Yesterday, Tuesday, saw some maximum temperatures in SA up to 10 and 11° above average, the largest variation at Coober Pedy which reached 29.9°, 11.6 above the July norm. New record or record-equalling high July temperatures were recorded at Leigh Creek and Roxby Downs in NE SA, while a tongue of the warm air had already reached SE VIC where Mallacoota and Mount Moornapa set or equalled July records. The warm and spring-like airmass has the potential to set more records into the weekend as it drifts east and continues to be fed by heat from the north, and is already doing so. Today, Moree Airport had its warmest July day in a 22 year history with a top of 25.7° just pipping a new record 25.6 set six days ago.
- Heavy showers moved through Perth today as a cold front moved across the city. They dropped 19.0mm in the Perth City gauge and 20.0mm at the airport in one hour just before midday, and were heavy enough for the weight of water to bring down a large shop awning in the inner northwestern suburb of Mount Hawthorn [ABC News].
World weather briefs
- China is in the grip of a record-breaking heatwave that is showing no signs of abating. Central and southern areas of the country entered the week with red alerts for high temperatures, the highest of the country's 4-tier warning system. Shanghai, one of the most populous cities in the world with a population of 24 million, had its hottest day in a 145-year history of observations last Friday, 21 July, when the temperature rose to 40.9°. Yesterday its maximum was 40.5°, the third time so far this month the temperature has risen over 40°. [Xinhua]
- Massive thunderstorms and flash flooding have accompanied the heat, such as this in the city of Yulin in Shaanxi province, 370km WSW of Beijing. Nearly continuous heavy rain and resulting flooding and mudflows have affected 45 counties in the far southern province of Yunnan since 19 July. Meteovesti†, quoting China Central Television, says that 10 people have died, 1,200 evacuated and 223,000 affected, while 200 buildings have been destroyed, and 2,400 more damaged.
- Tropical storm Sonca-17 made landfall on the central Vietnam coast yesterday in Quang Tri Province, 500km S of Hanoi. Maximum sustained wind speed as the storm moves into Laos is expected to diminish to about 55km/h so rainfall across the country, already suffering from flooding and damage from Tropical Cyclone Talas between 14 and 17 July, is the main concern. UNITAR-UNOSAT estimates just over three million people live within the 60km/h wind footprint with 250 to 500mm of rain forecast to fall in the mountains behind the coast. Both that link and this from ECHO give a map of the situation.
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.