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 is 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.
Weekly Tropical Climate Note
Issued on Tuesday 18 November 2014
First tropical cyclone for the season develops over the southwest Indian Ocean
Tropical convection this past week has been below average over much of South–East Asia and slightly elevated over parts of the southwest Indian Ocean. Severe tropical storm Adjali, which developed near Diego Garcia in the southwest Indian Ocean in recent days, has become the first named storm for the season in the Indian Ocean, south of the equator. Tropical storm Adjali is predicted to move south then southwest, slightly intensifying over the coming day before weakening as it moves over cooler waters.
An active Madden—Julian Oscillation
This past week, a Madden—Julian Oscillation (MJO) signal strengthened over Africa before weakening. Hence, it is possible the recent MJO activity contributed to the development of tropical storm Adjali and the recent supressed conditions over tropical parts of South–East Asia and the western Pacific Ocean.
Climate models indicate the MJO will move east over the Indian Ocean this week, however, there are a range of predictions of the MJO's likely strength. Some models suggest a clear signal, while others suggest the signal will be weak or indiscernible and unlikely to influence tropical weather. When the MJO is active over the Indian Ocean, it typically enhances convection over the Indian Ocean, while suppressing convection over tropical parts of South–East Asia, northern Australia and the western Pacific Ocean.
If the MJO continues to move east and remains active, there is a chance that it will enhance tropical convection in the Australian region from the end of November or start of December. However, MJO outlooks beyond a fortnight should be treated with considerable caution, as there is significant uncertainty surrounding the predicted strength and speed of movement of this current MJO signal.
See the Bureau's MJO Monitoring for more information.
Tropical Pacific Ocean moves closer towards El Niño
The Pacific Ocean has shown some renewed signs of El Niño development. International climate models expect this situation to persist, with most models predicting values near El Niño thresholds for the next two to three months. The latest NINO3.4 sea surface temperature anomaly is +0.9 °C and the 30-day Southern Oscillation Index value to 16 November is −10.9.
Regardless of whether or not El Niño fully develops, some El Niño–like impacts remain likely. For northern Australia, this means an increased likelihood of drier than usual conditions over the coming months, including an increased chance of the monsoon commencing later than usual.
See the Bureau's ENSO Wrap up for official El Niño information.
Next update expected by 25 November 2014 | Product Code IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
Product Code: IDCKGEWWOO