IDD20730 Australian Government Bureau of Meteorology Northern Territory Darwin RSMC - Australia

El Nino-Southern Oscillation Update
The 30-day Southern Oscillation Index [SOI] to February 7 is -22. Contributing pressure anomalies are +0.6 hPa at Darwin and -4.0 hPa at Tahiti. The sudden rapid decline in the SOI can be partly attributed to several tropical disturbances affecting French Polynesia [including Severe Tropical Cyclone Oli which passed over the Tahitian islands], where negative anomalies at Tahiti have plummeted to -4.0 hPa.
The monthly SOI for January was -10, and its 5-month running mean [centred on November] was -7.

The Pacific Ocean sea surface temperature [SST] and sub-surface temperature pattern is typical for an El Niņo event. SSTs remain warmer than the long-term mean across the equatorial Pacific Ocean, with the largest positive anomalies occurring close to the dateline. However, overall the area of positive anomalies have contracted over the last month. The sub-surface of the eastern tropical Pacific Ocean also remains warmer than the long-term average but it too has shown an overall cooling trend over the past month. Sub-surface anomalies in the equatorial eastern Pacific are now around 1-3 °C above normal.

For more information about the current state of El Nino - Southern Oscillation [ENSO] see the Bureau's "ENSO Wrap-Up" at www.bom.gov.au/climate/enso/ which includes a compilation of computer model predictions of ENSO.

Intra-Seasonal Patterns
An active Madden-Julian Oscillation [MJO] signal entered Maritime Continent longitudes during the first week of January and contributed to an active monsoon burst over northern Australia. During the second week of January the MJO signal weakened and its eastward progression stalled over the Maritime Continent. The MJO signal strengthened in the third week and continued to track eastwards again, into the western Pacific Ocean.

Over the past couple of weeks, the MJO has remained active and quasistationary over the warm SSTs in the western Pacific. The expectation is that the MJO will track east into the western hemisphere towards the end of this week. A suppressed phase of the MJO, currently located over Australian longitudes, is expected to persist across northern Australia for another week or so. Typically, a suppressed phase of the MJO coincides with a reduction in broadscale rainfall across Northern Australia.

Although there is a moderate level of uncertainty associated with current computer model forecasts of the MJO, the next active phase of the MJO to enter Australian longitudes is likely to be towards the end of February / start of March.

* Darwin RSMC chart area extends from 40S to 40N, 70E to 180
The Weekly Tropical Climate Note is updated each Tuesday by about 0330 UTC.
http://www.bom.gov.au/climate/tropnote/tropnote.shtml
For more information please contact climate.tropical@bom.gov.au