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.
First wet-season rains over Australia's Top End
The first week of the official northern wet season has seen relatively widespread rainfall over the northern half of Northern Territory and Queensland. Many locations had 10 mm or greater in the seven days to 6 October, with some locations recording more than 50 mm. The general increase in humidity and shower activity is indicative of an ongoing transition to a wet-season-like weather pattern.
Pacific Ocean continues to be a focus for tropical cyclone activity
The Pacific region continues to be a focus for tropical cyclone activity, despite a weak Madden—Julian Oscillation (MJO) signal. In recent days typhoon Mujigae made landfall on the southern China coast, causing flooding and generating winds reported at 180 kilometres per hour. Earlier in the week, Mujigae impacted the northern Philippines, with widespread damage in both countries. Typhoon Mujigae also spawned several violent tornadoes in its outer rain bands as it made landfall in China’s Guangdong province, causing significant damage.
Tropical storm Choi-wan may impact northern Japan in the next few days below typhoon intensity; other tropical systems currently over the Pacific Ocean are not forecast to have significant impacts in the short term.
The MJO signal remains weak or indiscernible. There is continuing disagreement between international climate models as to the forecast location of the MJO signal; however, there is strong model consensus that the signal will remain weak over the next two weeks. If the MJO signal remains weak in the near-term, the dominant driver of tropical activity in the Australian region is expected to be the warm waters of the tropical Pacific Ocean, related to El Niño.
See the Bureau's MJO Monitoring for current MJO information.
Positive Indian Ocean Dipole and El Niño in tropical Pacific Ocean
The 2015 El Niño continues to dominate the Pacific Ocean, while a positive phase of the Indian Ocean Dipole (IOD) has developed in recent weeks. The combination of El Niño and a positive IOD typically leads to drier-than-average conditions across much of northern Australia, particularly over Northern Territory and Queensland. The Australian monsoon-onset date is also typically later than average.
In recent climate outlooks, the influence of near-record warmth in the Indian Ocean appears to have had a moderating effect on the influence of El Niño and the positive IOD. As the positive IOD phase has matured, however, the trend to drier conditions has become more pronounced. Four out of five international models suggest this positive IOD event will persist through November.
To 4 October, the 30-day SOI is -21.9 and the 90-day SOI is -18.6. The latest weekly NINO3.4 sea surface temperature anomaly is +2.1 °C for the week ending 4 October.
See the Bureau of Meteorology's ENSO Wrap-Up for official El Niño information.
Product code: IDCKGEW000
ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.
Product Code: IDCKGEWWOO