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Tropical activity ramping up in the northwest

Craig McIntosh, Saturday December 5, 2020 - 11:24 EDT

Australia's northwest could be in for severe weather next week, with the possibility of the first tropical cyclone of the season forming over Australian waters.

For the last couple of weeks, the tropics have been relatively dry for this time of year. A big factor was the Madden-Julian Oscillation (MJO) being far off Australia and over the Indian Ocean. The MJO is an eastward moving disturbance near the equator that generates higher rainfall and can initiate tropical cyclone activity as it passes every 30-60 days. When it is over the Indian Ocean, Australia's tropics tend to be drier. When it is in our neighbourhood, which it is now, systems like monsoon troughs, tropical lows and cyclones are a higher chance of forming.

A tropical low looks like forming in a trough near Christmas Island over the coming days. There is a chance this low may move southeast towards the WA coast early next week, and there is also a chance this low may strengthen as it moves through favourable conditions of deep, warm water and weak winds.

As with most complex systems like this, models tend to disagree on strength and positioning this far out. A tropical cyclone is not guaranteed, but at least a tropical low or two should form in this trough and move towards northwest WA. If a tropical cyclone does form, it will be called Imogen.

Image: a possible tropical low/cyclone near northwest WA on Thursday, 10th of December, using the ECMWF MSLP and precipitation layer.

People living in WA's Kimberley, Pilbara and Gascoyne should pay particular attention to upcoming forecasts, as even if a tropical cyclone doesn't form, any tropical low can still pack a punch if it crosses the coast.