Weekly Tropical Climate Note

Severe tropical cyclone Debbie impacts Queensland

Severe tropical cyclone Debbie is the first tropical cyclone to reach severe status (category 3 or higher) since the Australian 2014-15 cyclone season. Debbie developed into a tropical low over the Coral Sea, and was first designated a tropical cyclone on the morning of 25 March. It attained a maximum intensity of category 4 and made landfall on the central Queensland coast, near Airlie Beach, around midday on 28 March.

An unofficial wind gust of 263 km/h was recorded at Hamilton Island airport on the morning of 28 March as Debbie made a direct impact on the site; if this observation is verified it would be the highest wind gust on record for Queensland. Heavy rainfall was also a feature in the Central Coast region with daily rainfall observations at multiple locations above 200 mm and a peak recording of 470 mm at Mount William, west of Mackay.

Debbie formed along a monsoon trough, which has been a persistent feature over northern Australia and adjacent waters during the last week. The environment in which Debbie formed was conducive for cyclone development, with a particularly favourable broadscale wind field apparent to the north and south of the system. This allowed Debbie to intensify significantly and become a large tropical cyclone, by Australian standards.

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 remained weak or indiscernible during the last week and did not contribute significantly to the development of Debbie or tropical cyclone Caleb, which attained tropical cyclone intensity near the Cocos (Keeling) Islands in recent days.

There is agreement between international climate models that the MJO will remain weak for the coming seven days. No other broadscale tropical climate influences are expected to significantly affect rainfall and cloud patterns over northern Australia and the Maritime Continent during this time. Rainfall variability is expected to be influenced by local winds and tropical activity associated with the monsoon trough in the region.

As Debbie dissipates over land in the coming days, the monsoon trough over northern Australia will break down and the region will move into an inactive phase of the monsoon. During this inactive or break period, shower and thunderstorm activity will become less frequent and more isolated over the northern tropics.

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

El Niño WATCH remains

The El Niño-Southern Oscillation (ENSO) is currently neutral. Recent fluctuations in the Southern Oscillation Index (SOI) can be attributed to movements in the monsoon trough and are not indicative of ENSO. Sea surface temperatures (SSTs) in the central and 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 there is an increased chance of El Niño forming later this year. As a result, the Bureau's ENSO Outlook status remains at El Niño WATCH.

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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