Weekly Tropical Climate Note

Tropical lows to bring rain to northern Australia

A monsoon trough currently extends across far northern Australia, between a tropical low over the Timor Sea and a second tropical low over the northern Coral Sea (see chart here). Widespread rainfall totals of more than 50 mm were observed in the northern Kimberley region of Western Australia, the Top End of the Northern Territory and far northern Queensland in the past week.

The monsoon trough is expected to remain in a similar location but weaken later in the week, reducing widespread rainfall over much of northern Australia. The focus of rainfall is expected to move to the vicinity of the tropical lows on either side of the continent. Rainfall impacts for the Australian mainland will heavily depend on the movement and degree of development of the lows. The tropical low over the Timor Sea is currently rated by the Bureau to have a high (>50%) chance to attain tropical cyclone intensity from Thursday this week, and may cross the Pilbara coast of Western Australia on Friday. The Coral Sea low is not expected to develop significantly in the next few days, but may strengthen towards the end of the week. Weather models also indicate that another tropical low, near the Cocos Islands in the Indian Ocean, may strengthen and develop into a tropical cyclone towards the end of this week.

For the latest update on tropical cyclones in the Australian region, go to the Bureau’s current tropical cyclones information.

Madden-Julian Oscillation remains weak

The Madden-Julian Oscillation (MJO) has been weak or indiscernible for most of the last week. Nearly all climate models surveyed by the Bureau predict the MJO signal will remain weak or indiscernible for the coming seven days. Tropical influences other than the MJO are also predicted to be weak during this time and have little effect on rainfall and cloud patterns over northern Australia and the Maritime Continent. In the coming week, the monsoon trough and associated tropical lows will be the primary influence on local wind and rainfall over tropical Australia.

For more information on the MJO, see the Bureau's current MJO monitoring information.

El Niño WATCH in place

Most atmospheric and oceanic indicators of the El Niño-Southern Oscillation (ENSO) are currently neutral. However, sea surface temperatures (SSTs) in the eastern tropical Pacific Ocean have warmed since the start of the year, and climate model outlooks suggest further warming of the tropical Pacific Ocean will occur in the coming months. These changes mean the likelihood of El Niño forming in 2017 has risen. As a result, the Bureau's ENSO Outlook status is now at El Niño WATCH.

If El Niño forms in the tropical Pacific Ocean, it is not likely to become established until the second half of 2017. However, waters more than 2°C above normal have been observed in the far eastern Pacific, along the South American coast.  This ‘coastal El Niño’ effect contributed to heavy rainfall and widespread flooding in Peru, causing multiple fatalities in recent days.

For northern Australia, overnight temperatures are typically cooler than usual during the dry season months of May to September in El Niño years.

See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.

 

 

 

Product code: IDCKGEW000

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