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.
Indian Monsoon weakens
A westerly monsoonal flow continues over the north Indian Ocean, maintaining the Indian and East Asian monsoons. However, the northwards advance of the Indian Monsoon stalled in the last week and recent rainfall over much of the Indian subcontinent and South East Asia returned to near-average levels. This occurred as a pulse of the Madden–Julian Oscillation (MJO) gained some strength over the tropical African region and western Indian Ocean. A weaker-than-normal monsoonal flow across the region is consistent with the typical impacts of an MJO over the western Indian Ocean.
The MJO signal weakened recently and is expected to collapse in coming days as it moves further eastwards across the Indian Ocean. Nearly all climate models surveyed by the Bureau agree the MJO will become indiscernible prior to moving into Maritime Continent longitudes.
See the Bureau's MJO Monitoring for current MJO information.
Negative Indian Ocean Dipole remains strong
Sea surface temperatures show a negative Indian Ocean Dipole (IOD) in the Indian Ocean. Recent weekly IOD index values are indicative of a strong negative event and climate models indicate the negative IOD will persist through to the end of spring. Rainfall across northern Australia, particularly over the Northern Territory and northern Queensland, is typically greater than normal in the September to November period during a negative IOD. A negative IOD typically also 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. El Niño-Southern Oscillation (ENSO) indicators in the Pacific Ocean remain neutral and while most climate models indicate the central Pacific Ocean will continue to cool, only two of eight models show La Niña values through the southern spring. 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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