Madden-Julian Oscillation (MJO)
The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.
MJO phase diagram
*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.
The MJO phase diagram illustrates the progression of the MJO through different phases, which generally coincide with locations along the equator around the globe. RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When the index is within the centre circle the MJO is considered weak, meaning it is difficult to discern using the RMM methods. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east. For convenience, we define 8 different MJO phases in this diagram.
Average weekly rainfall probabilities
These maps show average weekly rainfall probabilities and expected 850 hPa (approximately 1.5 km above sea level) wind anomalies for each of the 8 MJO phases. Green and blue shading indicates higher than normal rainfall would be expected, while red and orange shading indicates lower than normal rainfall would be expected. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is. The relationship of the MJO with Australian rainfall and winds changes with the season (which can be selected at the top).
Average outgoing longwave radiation (OLR)
Outgoing longwave radiation (OLR) is often used as a way to identify tall, thick, convective rain clouds. These maps show the difference from expected cloudiness based on the position of the MJO. The violet and blue shading indicates higher than normal, active or enhanced tropical weather, while orange shading indicates lower than normal cloud or suppressed conditions. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is. The relationship of the MJO with tropical weather patterns changes with the season (which can be selected above the maps).
Global maps of outgoing longwave radiation (OLR)
Global maps of outgoing longwave radiation (OLR) highlight regions experiencing more or less cloudiness. The top panel is the total OLR in Watts per square metre (W/m²) and the bottom panel is the anomaly (current minus the 1979-1998 climate average), in W/m². In the bottom panel, negative values (blue shading) represent above normal cloudiness while positive values (brown shading) represent below normal cloudiness.
The graphs linked to this map show the OLRs for the different regions within the Darwin RSMC area. The horizontal dashed line represents what is normal for that time of year (based on the 1979 to 1998 period). The coloured curve is the 3-day moving average OLR in W/m². Below normal OLR indicates cloudier than normal conditions in this particular area, and is shown in blue shading. Above normal OLR indicates less cloudy conditions and is shown in yellow shading.
Postscript: Coral Sea Dateline Fiji Guam & Marianas Indochina Malyasia & Indonesia Micronesia Nauru & Tuvalu New Guinea Northern Australia Philippines Solomon Island Southern India & Sri Lanka Vanuatu
Daily averaged OLR anomalies
Westerly wind anomalies
Time-longitude plots of daily averaged OLR anomalies (left) and 850 hPa (approximately 1.5 km above sea level) westerly wind anomalies (right) are useful for indicating the movement of the MJO.
How to read the Time-Longitude plots
The vertical axis represents time with the most distant past on the top and becoming more recent as you move down the chart. The Horizontal axis represents longitude.
Eastward movement of a strong MJO event would be seen as a diagonal line of violet (downward from left to right) in the OLR diagram, and a corresponding diagonal line of purple in the wind diagram. These diagonal lines would most likely fall between 60°E and 150°E and they would be repeated nearly every 1 to 2 months.
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.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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