December Rainfall Above Average In Coastal North And Far North Qld
December rainfall was above average for coastal northern Queensland, largely as a result of tropical cyclone activity, and an active monsoon trough across the Coral Sea towards end of the month.
Rainfall was also above average for much of Victoria and adjacent southwest New South Wales and border regions of South Australia. Further west, a large area spanning southeastern Western Australia and northwestern South Australia also had above average rainfall.
Rainfall for December was below average across much of Queensland away from the east coast, northern New South Wales, northeastern to central southern South Australia, across the Northern Territory, and across much of northern and the inland west of Western Australia.
Rainfall for 2018 as a whole was exceptionally low over the southeastern quarter of the mainland, with much of the region experiencing totals in the lowest 10% of records.
Significant rainfall deficiencies continue to affect large areas of eastern Australia at timescales out to around two years' duration. Annual rainfall was the seventh-lowest on record (since 1900) for the Murray-Darling Basin.
For the week to 8 January 2019, rainfall was recorded in isolated parts of western, southwestern and southeast Queensland.
At the start of the week, tropical cyclone Penny, which had previously made landfall on the afternoon of 1 January on the western side of Cape York Peninsula and quickly moved through the far north Peninsula as a tropical low, regained tropical cyclone strength in the northwest Coral Sea the next day.
A broad surface trough extended from southwest Queensland through to southeast New South Wales, and triggered thunderstorms in southwest Queensland, northwest and central parts of New South Wales. An onshore flow brought light showers to parts of the southeast Queensland coast.
During the middle of the week, broad areas of low pressure lingered over northern Australia, and combined with very moist and unstable air to produce isolated showers and embedded thunderstorms.
Another trough extended from inland Queensland to southeastern Australia. Thunderstorms and showers produced widespread light falls from inland southern Queensland, and parts of central to the southeast coast of New South Wales, to eastern Victoria, with heavier falls reported along the central coast of New South Wales.
In the north, showers and thunderstorms with moderate falls were recorded in the Kimberley in Western Australia, the Top End in the Northern Territory, and the Cape York Peninsula in Queensland. The slow-moving ex-tropical cyclone Penny in the central Coral Sea changed its track and moved westward towards to Queensland coast, bringing moderate falls to the central coast at the end of the week.
The highest weekly total 269 mm at Horn Island in the far northern Cape York Peninsula. Rainfall totals in excess of 100 mm were recorded in the northern Cape York Peninsula, and parts of the Kimberley in Western Australia.
Rainfall totals between 50 mm and 100 mm were recorded across most of the Kimberley in Western Australia, in parts of the northwest and the Top End of the Northern Territory, areas of the Gulf Country and much of the Cape York Peninsula.
Rainfall totals between 10 mm and 50 mm were recorded in parts of the Pilbara and remaining areas of the Kimberley in Western Australia; most of the northern half of the Northern Territory; much of the Gulf Country and Cape York Peninsula; isolated pockets of western, southern and southeast Queensland; in parts of the northwest, northeast, and from central to southeast coast New South Wales; pockets of eastern Victoria, and a small area in western Tasmania.
Little or no rainfall was recorded in remaining parts of Western Australia, the southern half of the Northern Territory, South Australia, and parts of inland Queensland, western New South Wales, western Victoria and most of Tasmania.
The year was very warm, and exceptionally so in December. Mean monthly temperature for December was the warmest on record for Australia, with prolonged periods of extreme heat, especially late in the month. Very warm temperatures across eastern Australia in the vast majority of months for the past two years have increased moisture stress, adding to the impact of low rainfall.
By Michelle Price