Weather News

What happened to Cyclone Joyce?

Ben Domensino, Friday January 12, 2018 - 14:03 AEDT

Tropical Cyclone Joyce moved over the west Kimberley coast on Friday morning as a category one system and is expected to move inland while weakening during the next 24 hours.

So what happened to the cyclone that was only yesterday expected to reach category three strength before making landfall?

Firstly, Cyclone Joyce actually did what it was forecast to do - it made landfall within an area the Bureau of Meteorology call the 'Region of Likely Tracks of Cyclone Centre,' also known as the 'cone of uncertainty.'

The most notable feature on the tropical cyclone forecast charts that you see on TV or computer screens is probably the forecast track line. This line represents the most likely path a cyclone will take and it is always shown within a cone-shaped shaded area.

While often overlooked, this shaded area is equally as important as the forecast track line itself. It represents all of the possible future tracks a cyclone may take, based on projections from a number of Australian and international computer models.

The forecast track line typically lies near the centre of this shaded area, representing the most likely path a cyclone will take. In reality, the cyclone could move anywhere within the Range of Likely Tracks of Cyclone Centre region.

In Cyclone Joyce's case, the system took a sharp turn to the left last night and followed a more southward track than yesterday's forecast track line had indicated. This trajectory caused the cyclone to move over the coast at category one intensity, well below the category three strength that was anticipated yesterday. It also reached the coast further east than originally expected.

While Joyce's path during the last 12 hours strayed from Thursday evening's forecast track line, it did fall within the Range of Likely Tracks shown on the forecast track maps.

Cyclone Joyce is a good example of why you need to know how to interpret cyclone warning information properly and consider all features on the Bureau of Meteorology's forecast track maps. In particular, be sure remember that the cone of uncertainty is just as important as the forecast track line.

- Weatherzone

© Weatherzone 2018

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