Asian Typhoons and Aussie Tropical Cyclones: What's the Connection?

Author: Chris Nitsopoulos

Posted on: Wednesday, November 15th, 2023, 2:07:21 PM

Ever wondered if a bustling typhoon season over in the Northwest Pacific could stir up cyclones closer to Australia? Well, you're not alone! We often get this question, especially since the mighty Typhoon Haiyan in 2013.

Here's the deal: It's not as straightforward as you might think. The Northwest Pacific, home to a whopping average of 26 tropical cyclones annually, is a hotbed of stormy activity. But does this influence the Coral Sea and Australia's cyclone season? Well, not necessarily.

Contrary to what you might expect, a busy typhoon season over there, especially east of the Philippines between July and October, doesn't guarantee a wild cyclone season in Eastern Australia. In fact, it could even mean the opposite. And if things are quieter in the Northwest Pacific, Queensland might brace for a more active cyclone season.

But why? It's all about the complex dance of ocean temperatures, atmospheric patterns, and a phenomenon called the El Niño-Southern Oscillation (ENSO). These factors can shift cyclone activities, influencing where and when these massive storms form.

For instance, a lively typhoon season can mess with the Walker Circulation and the Pacific's temperature balance. It can cool down the La Niña and amp up El Niño. This means the intense typhoons could lead to stable air over Northeast Australia, the Coral Sea, and the Solomon Sea, particularly in spring and summer.

Check out the complicated diagram below of how all the moving bits fit together and our attempt to simplify what it means below
 
https://www.nature.com/articles/s41467-019-11720-w/figures/10

Imagine the ocean as a giant bathtub, where the temperature of the water can affect the weather above it. In a specific part of the Pacific Ocean, known as the Niño 3.4 region, scientists track how warm or cool the water is over a three-month period. This temperature can change due to tropical cyclones (aka typhoons) swirling over the western part of the North Pacific Ocean.

Now, think of the Walker Circulation as a big air current that usually moves in a specific pattern over this region. However, when tropical cyclones occur, they can mess with this air current. They do this by creating unusual wind patterns that don't flow as they typically would. These winds can weaken the Walker Circulation.

There's also another air circulation pattern, similar to the Hadley Circulation orientated from north to south across the equator, that can be affected over the tropical western Pacific. This circulation involves air rising and falling in different areas, shown in the diagram with red arrows going up and blue arrows going down.

Next, let's talk about the thermocline. It's like an underwater boundary layer where the warmer upper water meets the cooler deeper water. Tropical cyclones can make this layer shallower in the western Pacific. Also, they can create waves known as Kelvin waves, which move warm water towards the east. This action deepens the thermocline in the eastern part of the Pacific.

All these changes – the messed-up air currents, the shifting thermocline, and the movement of warm water – can make an El Niño event (a period of warmer ocean temperatures) stronger. Conversely, they can weaken a La Niña event (a period of cooler ocean temperatures). It's like the tropical cyclones are nudging the ocean's thermostat, making El Niño turn up the heat and a La Niña weaker. 

So, while there's a link between the two regions, it's a complex web of climate dynamics, not a straightforward cause and effect. Understanding this is crucial, especially for those in the path of these powerful natural phenomena.

Stay curious and keep asking great questions! And hey, for more in-depth and accurate weather forecasts, especially during the 'Big Wet' in Northern Australia, consider joining us as an OCC subscriber. Your support helps us chase down the facts and share the wonders of our dynamic weather.