ENSO Update

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Bulletin December 2016 - Summary

The El Niño-Southern Oscillation (ENSO) remains neutral. However ENSO Outlook status is at El Niño WATCH, indicating around a 50% chance of El Niño developing in 2017.

All international models surveyed suggest that the current steady warming of the tropical Pacific Ocean is likely to continue in the coming months. Seven of eight models indicate that sea surface temperatures will exceed El Niño thresholds in the second half of 2017.

The Madden-Julian Oscillation (MJO) has been weak or indiscernible since mid-February. International climate models favour the MJO remaining weak for the coming seven days.

The Intertropical Convergence Zone (ITCZ) was slightly north of its long-term average position in the western Pacific and suppressed near and east of the Date Line in March. In the south Pacific, the South Pacific Convergence Zone (SPCZ) was close to its long-term average position, except near the Date Line where it was displaced towards Fiji. The SPCZ also extended much further east than normal to the Southern Line Islands.

Seasonal rainfall outlooks for April to June 2017 favour above average rainfall for Palau, western Federated States of Micronesia, southern and eastern Papua New Guinea, Solomon Islands, central and southeastern Kiribati.

The four-week coral bleaching outlook from 2 April indicates bleaching development and intensification to the north and east of Papua New Guinea, with this area of bleaching extending southeast to southern French Polynesia.

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Bulletin December 2016 - El Nino Oscillation

The El Niño-Southern Oscillation (ENSO) remains neutral. The ENSO Outlook status is at El Niño WATCH, indicating around a 50% chance of El Niño developing in 2017.

Sea surface temperatures (SSTs) in the central and eastern tropical Pacific Ocean have warmed steadily since the start of the year. In waters near the South American coastline, some areas are now at least 3 °C above average. However, all indicators of ENSO remain within neutral levels.

In the atmosphere, recent fluctuations in the Southern Oscillation Index (SOI) can be attributed to movements in the monsoon trough associated with severe tropical cyclone Debbie, and are not indicative of ENSO.

All international models surveyed suggest that the current steady warming of the tropical Pacific Ocean is likely to continue in the coming months. Seven of eight models indicate that sea surface temperatures will exceed El Niño thresholds during the second half of 2017. However, some caution must be exercised as models have lower accuracy at this time of year.

The 30-day and 90-day Southern-Oscillation Index (SOI) values to 1 April were +5.5 and +1.0 respectively.

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Bulletin December 2016 - MJO

The Madden-Julian Oscillation (MJO) has been weak or indiscernible since mid-February and did not contribute significantly to the development of tropical cyclones Debbie and Caleb.

The international climate models favour the MJO remaining weak for the coming seven days.

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Bulletin December 2016 - Cloud

The March 30-day OLR and TRMM anomaly maps suggest the ITCZ was slightly north of its long-term average position in the western Pacific and suppressed near and east of the Date Line.

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Bulletin December 2016 - Rainfall

Rainfall for the past month was normal for Sola, Pekoa and Aneityum. Below normal rainfall was recorded at Lamap, Bauerfield , Port Vila and Whitegrass.

Using NINO 3.4 SST Anomalies;

The outlook for Sola, Lamap and Anetyum favour above normal rainfall for the coming months with normal being the next most likely.

The outlook for Pekoa and Port Vila favour close to equal chances of normal and above normal for the coming months.

The outlook for Bauerfield favours normal for the coming months with above normal being the next most likely.

The outlook for Whitegrass favours below normal with equal chances of normal and above normal for the coming months.

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Bulletin December 2016 - SST

For the week ending 23 April, sea surface temperatures (SSTs) in the central equatorial Pacific Ocean were close to average. Warm anomalies were present in the far western Pacific, around eastern Australia and in the eastern Pacific. Anomalies greater than +1 °C were located adjacent to South America; these anomalies have cooled over the past few weeks.

Warm SST anomalies also persist across much of the Pacific south of the equator.
The NINO 3.4 region warmed by 0.2 °C in the past fortnight. The NINO3 SST anomaly for the week ending 23 April was +0.7 °C, with NINO3.4 +0.5 °C and NINO4 +0.2 °C.

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Bulletin December 2016 - MSLP

The March mean sea level pressure (MSLP) anomaly map shows anomalies greater than 1 hPa above normal over Papua new Guinea and further southeast over the southern Solomon Islands, Vanuatu and Fiji. Anomalies greater than 1 hPa below normal were present in the central tropical Pacific east of 160°W.
Areas of above (below) average MSLP usually coincide with areas of suppressed (enhanced) convection and rain throughout the month.

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Bulletin December 2016 - Model Outlooks

The APEC multi-model average, UKMO and ECMWF models favour above average rainfall for Palau, western Federated States of Micronesia, southern and eastern Papua New Guinea, Solomon Islands, and central and southeastern Kiribati.

The APEC multi-model outlook is an average of nine dynamical models: APCC, CMCC, CWB, IRI_CA, MSC, NASA, NCEP, PNU and POAMA.

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Bulletin December 2016 - SPCZ

In the south Pacific, the SPCZ was close to its long-term average position except near the Date Line where is was displaced towards Fiji. The SPCZ also extended much further east than normal to the Southern Line Islands (Kiribati).

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