Australian Weather

28 Aug 2024, 3:51AM UTC

Gale force west to northwesterly winds are creating havoc at Sydney airport on Wednesday afternoon, with all six landing and takeoff options impacted by very strong cross winds.   Sydney airport saw gale force west to northwesterly mean wind speeds of 65km/h at 12:30pm, while the site has been gusting up to 82km/h.   These winds are too strong for all three runways (six landing and takeoff options) to be used safely, airport traffic typically peaks during light winds. The image below shows that two of Sydney Airport’s parallel runways are orientated from north to south, and one single runway runs from west to east.    Image: Sydney Airport runway orientation showing two parallel runways running north/south and one west/east, Source: Sydney Airport   The west-east runway is the longest and can accept the largest aircraft, the A380. The gale force west to northwesterly winds on Wednesday are causing around 25 knots of crosswind on each of the six runway options.    Image: Weatherzone’s cross wind calculator in our Aviation Dashboard showing cross wind or X wind of 24 to 25 knots.  The term ‘crosswinds’ refers to winds that blow perpendicular to the runway, which can generate a significant lateral force on the aircraft, making it difficult for pilots to maintain a stable trajectory. The strong crosswinds can cause the plane to drift off course, posing a serious risk to both the aircraft and its passengers.   Sydney Airport typically changes runways when there’s sustained crosswind gusts above 20 knots (37km/h).    However, on Wednesday crosswinds are affecting all runways, meaning that aircraft are often opting to use the two north-south runways to increase traffic. This has meant that some flights have tried twice to land in these difficult conditions.   It is very rare for crosswinds to impact all runways and therefore this event is causing significant disruptions at the airport on Wednesday.   This event is not isolated to the Sydney area, numerous severe weather warnings for gales and damaging and/or destructive winds are in place across four states and the ACT, as a strong cold front lashes Tasmania and southeastern parts of the continent.    So when will these winds die down?  Conditions will ease somewhat by Wednesday evening, but not before the Sydney airport peak hour between 5 and 7pm. Winds will intensify again on Friday and into the weekend as further fronts whip through southern parts of the country. 

23 Aug 2024, 5:01AM UTC

Hundreds of millimetres of rainfall are forecast for western Tasmania in the next week, which will help replenish hydroelectric lakes in the region after some of the lowest rainfall on record.  Hydropower is Tasmania’s main source of electricity, with frequent rain filling Tassie Hydro’s 54 major dams and feeding into 30 hydropower stations. In fact, during winter, the state usually exports electricity to Victoria, via the underwater Basslink. In summer, when it is usually drier, the state relies on the National Electricity Market (NEM) for a top up of power.   Image: Hydroelectricity dam at Strathgordon in Tasmania  According to Hydro Tasmania, they produce around 9000 gigawatts of clean renewable electricity from hydropower, enough to power 900,000 homes or businesses.  The map below shows the catchments and power stations scattered across Tasmania; the largest lakes used for hydro are the Great Lake and Gordon-Pedder. The rain that falls in these catchments or dams is collected and used to generate electricity.   Image: Hydro catchment areas. Source: Hydro Tasmania  Usually, the west coast of Tasmania is the wettest due to prevailing westerly winds from cold fronts passing over the state, which tend to be blocked by vast mountains through central areas. During the past three months, unfortunately, this has not been the case for the west coast. Overall, the area has seen below average rain, reaching record lows in the far northwest, while the east coast saw average to above average rain.   Image: Tasmania rain deciles between May 1 and July 31, 2024. Source: Bureau of Meteorology  During July 2024, rain in western and central Tasmania was in the lowest 10% of Julys since 1900.  The below average rain has affected water storage across western Tasmania, with some areas seeing record low or very much below average streamflow. The Great Lake was only 25.1% full by the end of July, which is a 10.4% decrease from the same time last year.    Image: Streamflow decile categories for July 2024. Source: BOM  The good news is that rain is on its way, with a complex low pressure system set to direct several cold fronts across the state in the coming week.  Western Tasmania is forecast to see around 100 to 200mm of rain in the next 7 days, which could help fill up the western lakes, including the Gordon-Pedder. Eastern Tasmania, however, will see slightly less rain, with widespread falls of 30 to 50mm and isolated falls of 60 to 80mm.   Image: Accumulated rain forecast for the next 7 days leading up to 10pm AEST on Thursday, August 29.   Some of these totals will fall as snow as a cold airmass moves over the state from mid to late next week.   Looking ahead, the rain should continue next Friday, August 30, and into the weekend as the low continues to linger over the region.