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.
Heavy rainfall for northern Australia
Parts of northern Australia had their highest on record July monthly rainfall totals during the last week. The highest totals were around the central Queensland coast, where some sites set new July daily and monthly rainfall records. Some sites near the Queensland coastal town of Yeppoon had more than 400 mm in 72 hours. Parts of the northwestern Northern Territory also received their highest July rainfall totals on record, but the amounts were relatively modest compared with the Queensland totals. The weather feature which produced the rain over coastal Queensland is forecast to move inland and generate further significant falls across central Queensland for the next two or three days.
Historically, heavy rainfall events have been a feature for eastern Australia in the May to August period following the breakdown of strong El Niños (e.g., 1998, 1983, 1973 and 1906), regardless of whether or not it is associated with a transition to La Niña. During this most recent event, the weather system responsible for the rainfall was assisted by the record warm waters which surround Australia's northern coast. These warm waters are a source of extra moisture – which is evaporated into the air and transforms into the clouds which generate the rain.
Indian Monsoon remains active
The northernmost extent of the Indian Monsoon currently lies over northern India. An active monsoon trough over the region has produced heavy rainfall in recent days, with flooding and multiple fatalities reported. While the strength of the monsoon flow over the Indian subcontinent has recently eased, the southwesterly winds associated with the monsoon have persisted over India and much of South-East Asia.
Most climate models indicate that the Madden–Julian Oscillation (MJO) will remain at moderate levels over the Indian Ocean for the next week, so monsoon flow over India is likely to continue and possibly be reinvigorated. Rainfall models suggest that northern India and adjacent regions may see further significant rainfall totals in the coming week. Typically, when the MJO moves over the Indian Ocean at this time of the year, cloudiness and rainfall is enhanced across an area of the northern hemisphere which extends from the Arabian Sea to South-East Asia. The presence of the MJO is expected to be relatively short-lived, with the majority of models indicating the signal will weaken over the Indian Ocean later this week.
See the Bureau's MJO Monitoring for current MJO information.
Negative Indian Ocean Dipole strengthens
Sea surface temperatures show a negative Indian Ocean Dipole (IOD) in the Indian Ocean. Latest values of the IOD index indicate that the dipole has strengthened in recent weeks. Climate models indicate that the negative IOD will persist through to the end of spring. A negative IOD typically brings warmer daytime and night-time temperatures to northern Australia. Find out more about the Indian Ocean Dipole.
In the tropical Pacific Ocean, although La Niña remains possible, recent model outlooks have eased back their forecasts for La Niña in 2016. Current observations do not show any indication that La Niña is underway, with all indicators within their neutral range. Recent observations, combined with current climate model outlooks, mean the Bureau's ENSO Outlook remains at La Niña WATCH. This indicates the likelihood of La Niña forming in the coming months remains at 50%. If La Niña develops, rainfall in the build-up months and during the northern wet season is typically above average over northern Australia.
See the Bureau’s ENSO Wrap-Up for official El Niño and La Niña information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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