WHILE hot, dry conditions continue to fuel fires in Victoria and South Australia, a monsoon trough has delivered heavy rainfall to the Top End. Visit FarmOnline Weather for more updates and information
Dangerous fire weather flaring through south
Catastrophic fire danger has hit parts of South Australia today with hot dry and gusty northerly winds.
Fire danger has reached Catastrophic levels today in the Mt Lofty Ranges and Lower South East, with Extreme levels likely across much of SA today and Victoria tomorrow.
The reason for the elevated fire danger is an approaching low pressure trough. This trough is drawing very hot northerly winds across the south of the nation, with wind gusts a risk to exceed 90 kilometres an hour in Victoria tomorrow.
The air is also very dry, with humidity dropping below 10 per cent at times across most of each state. Any fires that spark up in these two states today or tomorrow are likely to be fast moving and uncontrollable.
Relief from the heat will slowly arrive on Saturday, with a southwesterly change reaching Adelaide mid-morning and then Melbourne in the late afternoon or early evening and later further inland.
Thunderstorms are likely to develop in SA and Victoria tomorrow near the cool change, with lightning a risk to start new fires.
On Sunday wind speeds will be lower, temperatures will be cooler and humidity will increase markedly, making fires easier to contain. This will give firefighters a chance to get on top of any out of control fires before a slightly weaker spell of heat moves into both states on Tuesday and Wednesday next week.
Monsoon trough brings heavy rain to the tropics
The much-anticipated monsoon trough crossed onto the upper Northern Territory on New Year's Eve, bringing a prevailing northwesterly flow and heavy rainfall.
Just after the New Year's Eve celebrations, the monsoon descended upon Darwin, causing 120 millimetres to fall on Darwin Airport and 156mm to Wagait Beach. This is just after Darwin had a below average December of just 108mm.
The monsoon trough is seen as a large, low-pressure convergence zone where moist northwesterly winds meet dry southeasterly winds; that is, a region where a clear and distinct change in the moisture content and direction of the winds occur.
This region dipped down from the Timor Sea, signalling the beginning of the monsoon season for the western Top End.
Weather forecasters watch this trough for embedded low pressure systems, some of which may later develop into cyclones.
The western portion of this monsoon trough should continue to traverse south over the coming weeks as it is being dragged by a low pressure cell, bringing moist winds to far north Western Australia while staying north of tropical Queensland.