The first tropical cyclone of the season for the Australian Basin will attempt to develop during the extended Christmas weekend.
The tropical cyclone will likely evolve from the large zone of unsettled weather across northern Australia over the warm waters of the Gulf of Carpentaria around or shortly after Christmas.
Prior to any tropical system taking shape, bands of heavy rain will stream into the Top End and far northern Queensland into Christmas. This includes Darwin.
Worse than creating slowdowns for travelers heading to their Christmas destinations, flash flooding can result.
"Any tropical system that forms over the Gulf of Carpentaria should be short-lived," Nicholls said.
The system will likely be steered ashore into far northeast Northern Territory or northwest Queensland around the beginning of the new week.
The strength of the cyclone will determine the extent of the wind damage, which coastal areas near landfall will be most at risk for.
The main concern from the budding tropical system, regardless of its strength, will be heavy rain.
"It appears that heavy rain and flooding will be concerns for areas from northeast Northern Territory to northern Queensland this weekend into early next week," Nicholls said.
This tropical system, however, will remain too far to the north to impact the start of the Rolex Sydney Hobart Yacht Race in Sydney Harbour on Saturday.
A cold front will be approaching Sydney on Saturday. At this point, the accompanying rain and thunderstorms are expected to hold off until after the start of the race but could bring a risk of lightning, rough seas and gusty winds to the yachts later in the day.
A landfalling tropical cyclone in Australia in late December is early considering the current El Niño pattern.
"In El Niño years, the first tropical cyclone to make landfall [in Australia] usually occurs in mid-January," Nicholls said.
El Niño occurs when ocean water temperatures rise above normal across the central and eastern Pacific, near the equator. It can impact the weather around Australia, leading to fewer tropical cyclones and an increased risk for an intense fire season.
Nicholls expects a total of eight tropical cyclones to form this season in the Australia Basin, below the average of 11.
"Despite a projected below-average season, there is a higher percentage chance of intense cyclones [gusts of 125 km/h (78 mph) or higher], which is typical of El Niño years," Nicholls said.