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.
Record warmth across northern Australia
Heatwave conditions continued across northern Australia last week. The extended period of widespread warmth has resulted in well above-average maximum and minimum temperatures being recorded across nearly all of northern Australia during November. A number of sites across northern Australia experienced their highest November monthly maximum temperatures.
The increased temperatures have contributed to an unstable atmosphere across the tropics, and many locations in northern Australia experienced heavy rainfall, mostly from isolated afternoon thunderstorms, over the past week. As a result of this rainfall, many parts of the north which had been experiencing below-average wet-season rainfall have now recorded near-average rainfall totals during November. Some parts of the Northern Territory, notably the far northern region, have had well below-average rainfall, but most parts of northern Australia had average to above-average totals during November. A significant proportion of northern Australia is still tracking below average for wet-season rainfall to date, particularly across the ‘Top End’ of the Northern Territory and central Queensland.
First tropical cyclone for southwest Pacific Ocean
Tropical cyclone Tuni formed near Samoa on 28 November and developed into the first tropical cyclone of the 2015-16 season in the southwest Pacific region (TC Raquel which formed in July 2015, is classified as forming in the 2014-15 season). Tuni brought heavy rainfall, some flooding and landslides to Apia, Samoa and the surrounding region, and then tracked toward Niue. The tropical cyclone underwent an extra-tropical transition and dissipated on 30 November before affecting any other islands.
While the Madden–Julian Oscillation (MJO) signal is currently weak, some international climate models surveyed by the Bureau indicate the MJO may strengthen and move near to Australian longitudes in the next two weeks. However, tropical convection in the Australian region is not expected to be significantly enhanced, as the MJO will be of relatively small amplitude and the broader climate drivers (including El Niño) are not favourable for above-average rainfall.
While the MJO pattern is expected to remain weak, forecast models suggest an increase in tropical convection in the central and southwest Pacific (along the South Pacific Convergence Zone) within the next week or two. This increase in activity may be enhanced by other tropical waves in the area.
See the Bureau's MJO Monitoring for current MJO information.
Strong El Niño continues
A strong El Niño persists in the tropical Pacific Ocean. International climate models suggest that El Niño sea surface temperatures (SSTs) are approaching their peak, and will decrease in the first quarter of 2016. With such warm SSTs, models suggest the tropical Pacific is unlikely to return to neutral until at least autumn 2016, although impacts on Australian climate are likely to decline prior to this.
In summer during El Niño, the Cape York Peninsula tends to have below-average rainfall, while the interior of Western Australia often sees above-average rainfall. Australia’s tropical north also tends to see a delayed onset of monsoon conditions during El Niño events.
Sea surface temperatures across the Indian Ocean basin remain very warm. 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.
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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