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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