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.
Negative Indian Ocean Dipole and La Niña-like pattern continues
In the Indian Ocean, the negative Indian Ocean Dipole (IOD) has weakened from its peak but continues to influence the climate of northern Australia. Models predict the IOD will return to neutral by November or December. During a negative IOD event rainfall across northern Australia is typically above average from September to November, with warmer daytime and night-time temperatures usually observed.
In the tropical Pacific Ocean, although the El Niño–Southern Oscillation (ENSO) remains neutral, the ocean and atmospheric display some patterns typically associated with La Niña. In particular, the ocean to the north and east of Australia is warmer than usual. The majority of international climate models monitored by the Bureau indicate the tropical Pacific is likely to remain at ENSO-neutral levels in the coming months. However, two models indicate weak La Niña levels will be reached, hence, the ENSO Outlook remains at La Niña WATCH. Even if La Niña thresholds are not met, the warmer water to the north of Australia means La Niña-like impacts are possible. During La Niña, northern Australia typically experiences above-average wet season rainfall, with the first rains of the season typically arriving earlier than normal.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and IOD information.
Average to above-average tropical activity for 2016-17 in Australian region
The 2016-17 tropical cyclone outlook for Australia predicts an average to above-average number of cyclones for the Australian tropical cyclone season (November–April). La Niña years are typically associated with above-average tropical cyclone numbers, and an earlier-than-normal date for the first cyclone to impact Australia.
Tropical activity continues in northwest Pacific Ocean
After two powerful typhoons affected the northwest Pacific region last week, a further two typhoons have developed in the area, typhoons Sarika (Karen) and Haima (Lawin).
Typhoon Sarika (Karen) is expected to make landfall at Hainan today, before a second landfall near the Vietnam-China border in the next 48 hours. Prior to these encounters, Sarika (Karen) caused significant damage and disruption to the northern and central Philippines where it made landfall on 16 October. Sarika (Karen) is expected to impact Hainan as a ‘strong’ typhoon with estimated wind speeds near the storm’s centre in excess of 135 km/h.
To the east of the Philippines is typhoon Haima (Lawin). It is tracking to the west and is expected to impact the northern Philippines in the next 48 to 72 hours with winds near the storm’s centre in excess of 200 km/h. Warnings and information on these systems can be found at the Japan Meteorological Agency website.
The recent tropical activity in the northwest Pacific Ocean brings the number of tropical storms or typhoons since the start of September to eleven (average number for September to October is between eight and nine). The tropical activity is occurring without the influence of a discernible Madden–Julian Oscillation (MJO) signal in the last week. Other tropical wave activity and the very warm waters in the region, combined with a persistent monsoon trough, are likely to be the main climate drivers responsible for the recent activity.
Most international climate models predict that the MJO will remain weak or indiscernible in the coming week, although one or two of the models surveyed by the Bureau of Meteorology predict the MJO will move into the western Pacific Ocean and strengthen slightly.
See the Bureau's MJO Monitoring for current MJO information.
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ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
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