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 characterized 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 3 December 2013
Warm Indian Ocean aids tropical weather
The Madden-Julian Oscillation (MJO) has remained indiscernible over the past week and is unlikely to have influenced tropical weather conditions during this period. The MJO has been weak or indiscernible since early October. When the MJO is weak or indiscernible, other secondary and often localised factors tend to influence the weather. For instance, record warm sea surface temperatures across the equatorial Indian Ocean are likely to have contributed to the widespread convection that has impacted on the region over the past fortnight.
The monsoon trough has recently weakened over northern Australia, with monsoon break conditions expected to become established over the tropical north of the country in coming days, which could last for up to two weeks.
Several of the climate models surveyed by the Bureau forecast a weak MJO to develop over the Indian Ocean this week, move eastward and enter the Maritime Continent region during the second week of December. Current cloud and wind patterns support this scenario. The risk of tropical cyclone development over the southeast Indian Ocean will be elevated under these conditions. This scenario would also increase the chance of a monsoon burst over northern Australia before the end of the year.
Other models indicate the MJO is more likely to remain weak and indiscernible in the coming weeks. In this case, the MJO would not be expected to affect tropical weather.
See the Bureau's MJO Monitoring for more information on location and tracking of the MJO.
ENSO state: neutral
El Niño—Southern Oscillation (ENSO) remains in the neutral state. A neutral ENSO period indicates that the tropical Pacific Ocean is not shifting the odds towards a significantly wetter or drier period for Australia. When ENSO is in a neutral phase, more localised weather extremes can and do occur due to the influence of secondary or local factors such as the position and strength of the monsoon trough.
The latest NINO3.4 sea surface temperature anomaly is +0.2 °C. The monthly Southern Oscillation Index (SOI) value for November was +9.2. The contributing pressure anomalies for November were +0.3 hPa at Tahiti and -1.1 hPa at Darwin. The SOI has been temporarily influenced by the southward movement of the monsoon trough over northern Australia.
See the Bureau's ENSO Wrap-Up which includes a compilation of computer model predictions of ENSO indices.
Next update expected by 10 December 2013| Product Code IDCKGEWOOO
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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