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.
Dry and hot conditions for northern Australia
Large parts of northern Australia have received less than 40% of their typical November rainfall so far this month. November rainfall deficiencies are severe over parts of the Northern Territory with some areas tracking lowest on record. Broad swathes of the Northern Territory have recorded maximum temperatures 2 to 4 °C above average, while minimum temperatures are up to 3 °C above average, particularly over the sub-tropics.
Forecasts suggest temperatures will remain above average over much of northern Australia, with an improved chance of widespread shower activity from later this week, particularly over northern Queensland and the Northern Territory.
Weak Madden–Julian Oscillation
In the last fortnight, the Madden–Julian Oscillation (MJO) briefly entered Australian longitudes but weakened rapidly and moved into the eastern Indian Ocean. Nearly all international climate models surveyed by the Bureau indicate the MJO will remain weak during the next two weeks.
The relative lull in tropical cyclone activity over the northern Pacific and Indian oceans continued last week as the typical northern hemisphere tropical cyclone season (May–November) drew to a close. Currently the strongest system in the northern hemisphere is typhoon In-Fa, east of the Philippines and forecast to move northeast towards Iwo To. The first southwest Indian Ocean tropical cyclone of the 2015–16 season, Annabelle, developed about mid-way between Australia and Madagascar; but weakened below tropical cyclone strength and is not forecast to intensify further.
Even with a weak MJO pattern, forecast models suggest an increase in tropical convection in the southwest Pacific (along the South Pacific Convergence Zone) within the next few weeks. This increase in activity may be enhanced by other tropical waves in the area.
See the Bureau's MJO Monitoring for current MJO information.
Indian Ocean Dipole dissipates
The positive Indian Ocean Dipole (IOD) pattern of the past three and a half months has rapidly decayed this week. The latest IOD index value is +0.13 °C which is well within neutral thresholds.
Furthermore, sea surface temperatures across the Indian Ocean basin remain very warm; the October sea surface temperature anomaly for the Indian Ocean was the highest positive anomaly for any month on record. This larger than normal area of warm Indian Ocean temperatures may, to some degree, counter the historical tendency for fewer tropical cyclones during strong El Niño events
A strong El Niño persists in the tropical Pacific Ocean. On average an El Niño summer brings below-average rainfall across northern Queensland and parts of Northern Territory. Australia’s tropical north also usually sees a delayed onset of monsoon conditions during El Niño events. Further, the focus of tropical cyclone activity in the Pacific usually shifts eastward with the warm waters of El Niño.
See the Bureau of Meteorology's ENSO Wrap-Up for official El Niño information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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