WA: TC Isobel crosses WA north coast. Tropical Cyclone Isobel crossed the northern WA coast near Pardoo, about 100km ENE of Port Hedland, soon after midday. The system continued to be a weak one, its central pressure on landfall estimated at 990hPa. It had the distinction of being multi-centred, which helped to keep it weak, but resulted in significant rain falling over a wider area. Cyclone warnings estimated winds near the cyclone would reach 100km/h; the highest recorded wind gust was 72km/h and sustained wind speed 63km/h at Barrow Island, well to the west of Isobel's track. Heavy rain preceded the cyclone during the day (see downpours) with by far the highest total 141mm between 9am and 3pm at Mandora, just east of Isobel's landfall. The cyclone weakened into a low pressure system almost immediately upon landfall, but its massive moisture and instability began interacting with a southern trough and unseasonably cold air advancing from the west as it moved into the Great Sandy Desert (see stories below and on 4 Jan 2007).
WA: Wintry outbreak brings record January cold. The north-south trough clearly visible through WA on the surface charts in The Day in Charts below fed vast amounts of moisture from TC Isobel into the state today, creating the extensive, deep cloudmass that dominates the satellite cloud images of Australia. At the same time, a tongue of very cold air for mid summer moved into the state from the southwest accompanied by a broad, deep upper low (see box below). Twenty-one centres, from the Gascoyne to the Central Wheatbelt and west to Perth, recorded their coldest-ever January day (see records). Perth Airport and Cunderdin, with around 60 years of climate history, both shaved half a degree off their previous records, while Dalwallinu (49 years) cut 1.7 and Wongan Hills (42 years) cut 2.6 off their previous lows.
|Some idea of the intensity of the WA cold airmass is given by the temperature readings at 850hPa (about 1.4km above sea level, and well away from surface heating effects) at 8pm WDT which indicated 28C at the Head of the Bight, but only 4C along the WA South West coast. Note the moisture streaming down through the eastern half of the state before curving around the base of the trough and returning northwards across SW WA, much envigorated by the colder air.
||The upper air situation at 500hPa at the same time shows the deep upper low cutting off from its parent Southern Ocean trough and covering the southwestern third of the state. The upper low further enhanced uplift across the region, thickening cloud and bringing rain and record cold temperatures underneath it -- compare this chart to the satellite images, and the solar radiation and maximum temperature anomaly charts in The Day in Charts section below. COLA
WA, SA: Hot around the Bight. In stark contract to conditions farther west, maximum temperatures in SE WA and southern SA today were up to 20C above average, with several centres reporting 40C+ readings (see hottest). Yulara recorded its highest January minimum temperature, 30.5C, in 17 years of record.
VIC: Bushfires continue as firefighters prepare for worse. Firefighters from Canada, New Zealand and the Northern Territory are converging on VIC in advance of expected worsening fire weather during the next few days. The Canadians have specialist knowledge in forest firefighting and helicopter operations. Some 45 fires have been started by lightning across the state over the past 2 days, but most have been extinguished or are controlled. One at Boulder Creek, north of the Princes Highway between Orbost and Cann River, is now about 500 hectares in size. It caused smoke problems on the Highway today and grew rapidly in size this afternoon. The Great Divide fire complex continues to burn at low levels, and work is concentrated on back-burning and maintaining control lines, especially along its southern flank in the Erica, Thomson Catchment and Swifts Creek areas.
QLD: SE catchments at record low. Recent rain in SE QLD has bypassed the main catchments for Brisbane and the Gold and Sunshine Coasts. The combined capacity of the dams is currently 23.7%, the lowest on record. Falls of around 50mm in the past two days in parts of the SE have not fallen in catchment areas, with North Pine recording 18mm but Wivenhoe and Somerset virtually nothing. At least 50mm is needed to saturate the soil before run-off can begin. Details of some significant falls in the 24 hours to 9am in SE QLD (and across the border on the NSW North Coast) are in wettest below.
Bureau summaries issued today
AUS: Bureau's annual climate statement shows 2007 a year of contrasts. The Bureau of Meteorology's Annual Climate Statement, released today, shows Australia's annual mean temperature for 2006 was the eleventh warmest year since 1910 while the global mean temperature is expected to be the sixth warmest since 1861. Average maximum temperatures have been the highest on record since 1950 in Victoria, South Australia, Western Australia and in the Murray-Darling Basin. Rainfall was well below normal in the southeast and far southwest, but close to normal when averaged over the whole country. Full report.
TAS: A year of extremes. The Tasmanian state annual summary points up an extraordinarily varied year across the state, with some sites reporting their driest year for 100 years. Hobart, Launceston, Burnie and Devonport all experienced their lowest annual rainfall since records began. Tasmania also experienced some record hot and cold temperatures, several extremely windy days and a number of unseasonal bushfires, snow, frost and hail events throughout the year. Full report.
WA: Also a year of extremes. While average rainfall across WA during 2007 was the eighth highest since 1900, this masked extremes from north to south. In much of the north it was an exceptionally wet year, while the west coast and South West experienced well below average rain with parts of the coastal fringe, including Perth, having their driest year on record. Full reports for the state and Perth.
NT: A tale of two Territories. The Northern Territory in 2006 saw conditions much cooler and wetter than normal in the north but hotter and drier than normal in the south. Full report.
ACT: Records fell during 2006. Canberra experienced record sunshine and record daytime heat during 2006, while the year was the national capital's fifth driest on record. Full report.
NSW: A hot and very dry year. 2006 was the tenth consecutive year of above average statewide maximum and minimum temperatures. In the Murray-Darling Basin, it was the third driest year since 1900, while daytime maximum temperatures were the second highest on record. In Sydney, maximum temperatures were the third highest on record. Full reports for the state and Sydney.
SA: An extremely dry 2006. 2006 over South Australia was one of the driest since records began with many stations recording only about 50% of their annual totals. In all but the far west below average annual totals were recorded. The mean temperature for 2006 over South Australia was 20.3C, 0.8 above the 1961−90 mean making 2006 the third warmest year since 1910. Full report.
TAS: December weather summary - Bushfires and very dry despite a late soaking. The Tasmanian weather summary for December shows that, apart from a few patches in the southeast and central midlands, December followed the trend of the past eleven months, with drier than average conditions across the state. Conditions were such that many bushfires burned out of control for many weeks, burning out forest and causing damage to houses and other buildings. Despite the wet and cold end, most of the state was still slightly warmer than average during the day and generally much colder at night. Full report.
WA: December weather summaries - an average month. The monthly rainfall and average temperatures across WA in December were close to normal, though there were some notable local departures from average. Perth, however, was warmer than normal. Full reports for the state and for Perth.