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.
Ex-tropical cyclone Alfred briefly in the Gulf of Carpentaria
Tropical cyclone Alfred became only the second named storm in the Australian region so far this season. In the lead up to Alfred's formation, a monsoon trough was active across Australia, with heavy rainfall affecting northwestern Australia ahead of the focus moving to the Gulf of Carpentaria region in the last week. Alfred began as a tropical low over the Carpentaria region of the Northern Territory about a week ago and reached tropical cyclone strength on the 20th after moving over water. By the morning of the 21st Alfred had weakened to a tropical low as it moved towards the coast near the Queensland-Northern Territory border. At its peak, tropical cyclone Alfred sustained winds near its centre of at least 85 km/h, with gusts to 120 km/h. The rain bands associated with the storm caused heavy rainfall and strong winds in the Gulf coast region, including over 460 mm at Centre Island and over 300 mm at Borroloola, both in the Northern Territory. Ex-tropical cyclone Alfred is expected to continue to weaken and track westward over the Northern Territory over the next few days.
So far, this tropical cyclone season has been surprisingly quiet. The Australian region typically sees around 11 named storms in an average season. A quiet season so far is no reason to become complacent. Tropical cyclones present a real risk for tropical northern Australia. The tropical cyclone season runs through the end of April and usually peaks near the end of February and early March.
Madden-Julian Oscillation weakens to moderate strength
After maintaining relatively high amplitude for nearly all of February, the Madden-Julian Oscillation (MJO) signal has recently weakened towards more moderate values. An MJO pulse is currently tracking eastward over the tropical western hemisphere and Africa region at moderate strength. Usually when the MJO is in that part of the world at this time of year, northern Australia and the Maritime Continent sees suppressed tropical convection, below average rainfall, and a decreased risk in tropical cyclone development. Tropical cyclone Alfred is an example of a tropical cyclone forming despite a less favourable broadscale environment.
The MJO is expected to continue its eastward progress over the next two weeks. However, models do not agree on the strength of the MJO as it crosses the Indian Ocean. Some models predict the signal to weaken completely before reaching Australian longitudes, while other models maintain a weak to moderate signal for the next two weeks while over the Indian Ocean.
For more information on the MJO, see the Bureau's current MJO monitoring information.
El Niño–Southern Oscillation remains neutral
The El Niño–Southern Oscillation (ENSO) remains neutral, with virtually all indicators close to their average values. In recent weeks, the central and eastern tropical Pacific Ocean has warmed at the surface, with most climate models suggesting this warming is likely to continue during the southern autumn.
However, this is the time of year when both ENSO and climate models have greatest variability. Some caution must be taken when using recent conditions, such as central Pacific warming, to determine likely conditions later in the year. This means either neutral or El Niño are the most likely ENSO state for the southern winter/spring.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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