Island Climate Update

A monthly summary of the climate in the tropical South Pacific islands, with an outlook for the coming months.

October-December 2024 Island Climate Update

There is a 60% chance that La Niña will develop by the end of December. Tropical Pacific trade winds will continue to nudge the ocean in a La Niña-like direction.

An alternative measure of central Pacific SSTs, called the relative oceanic Niño Index, has had an average anomaly of -0.7˚C over the last month and is more aligned with La Niña-like oceanic conditions.

As of 17 September, the traditional 30-day Niño 1+2 Index anomaly was -0.16˚C, within the neutral range. The 30-day NINO3.4 Index anomaly (in the central equatorial Pacific) was -0.17˚C, also in the neutral range.

The Southern Oscillation Index (SOI) was in the neutral range during July-September (0.0), while the September value was -0.2 (in the neutral range).

The subsurface equatorial Pacific continues to be 3˚C to 5˚C cooler than average just below the surface in the east of

the basin.

Above average upper oceanic heat content continues in western parts of the basin. The West Pacific Warm Pool is becoming more unusually warm, which is also reflective of the potential development of La Niña.

The South Pacific Convergence Zone was generally close to its climatological normal position during September.

During October-December, model guidance favours an enhancement in convective forcing over the western Pacific and Maritime Continent, consistent with a developing La Niña. This may lead to enhanced rainfall for some countries such as Palau, Federated States of Micronesia, Papua New Guinea, and the Solomon Islands (based on the decile precipitation forecast for October and October-December; see pages 6-7 for more information).

Tropical cyclone season starts in November. While no out-of-season activity is forecast at this time, it is a reminder to remain vigilant and prepared as tropical cyclone season approaches.

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Additional resources

Additional regional and country situation summary and forecast information can be obtained below. Current rainfall accumulation status and other derived summary information are updated on a daily basis (with a 2-day lag), with seasonal forecast information updated once per month.

About the Island Climate Update

NIWA is the Network co-lead for the WMO RA V Regional Climate Centre Node on Long Range Forecast and consortium member for nodes on Climate Monitoring, Operational Data Services and Training.

Development and production of the ICU is supported by NIWA Strategic Science Investment Funding under contract PRAS2301. The Island Climate Update bulletin and associated video and products are prepared as soon as possible at the start of each month. Delays in data availability occasionally arise. While every effort is made to verify the data, NIWA does not guarantee the accuracy and reliability of the analysis and forecast information presented and accepts no liability for any losses incurred through the use of this bulletin and its contents. The contents of this bulletin and all associated products produced by the Island Climate Update may be freely disseminated provided the source is acknowledged.

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View past monthly Island Climate Update issues (2001 to present) here Island Climate Update | NIWA

Issues

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    Island Climate Update 288 - October 2024

    There is a 60% chance that La Niña will develop by the end of December.
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    Island Climate Update 287 - September 2024

    ENSO neutral conditions are expected to continue over the next several weeks, but La Niña is slightly favoured over ENSO neutral during September-November.
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    Island Climate Update 286 - August 2024

    ENSO neutral conditions are expected to continue over the next couple of months, but La Niña is slightly favoured over ENSO neutral during October-December.
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    Island Climate Update 285 - July 2024

    ENSO neutral conditions are expected to continue over the next 2-3 months, but La Niña is favoured to develop during October-December.
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    Island Climate Update 284 - June 2024

    El Niño has continued to weaken during May, and ENSO neutral conditions are favoured to develop by June 2024.
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    Island Climate Update 283 - May 2024

    El Niño continued to weaken during April, and ENSO neutral conditions are favoured to develop by June 2024.
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    Island Climate Update 282 - April 2024

    El Niño continued during March but continues to weaken. ENSO neutral conditions are favoured to develop by June 2024.
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    Island Climate Update 281 - March 2024

    The El Niño event is now past its peak oceanic intensity and it is likely to weaken further during March.
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    Island Climate Update 280 - February 2024

    El Niño was active during January and will very likely continue over the next three months.
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    Island Climate Update 279 - January 2024

    El Niño continued during December and has around a 100% chance of persisting through March.
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    Island Climate Update 278 - December 2023

    El Niño continued during November and will likely remain in place during the next three months.
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    Island Climate Update 277 - November 2023

    El Niño continued during October and will likely intensify during the next three months.
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    Island Climate Update 276 - October 2023

    El Niño has officially arrived. A majority of NIWA’s criteria for classifying an El Niño event were satisfied during September.
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    Island Climate Update 275 - September 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of August was +1.34˚C. The weekly value reached +1.5˚C at the end of the month – the traditional threshold for a strong oceanic El Niño.
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    Island Climate Update 274 - August 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of July was 1.11 ˚C . At the same point during the developmental phase of strong past El Niño events , it was +1.35˚C in 2015, +1.31˚C in 1997, and +0.26˚C in 1982.
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    Island Climate Update 273 - July 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of June was +0.93˚C. This is warmer than it was at the same time during the development of strong El Niño events in 1997 and 1982.
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    Island Climate Update 272 - June 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of May was 0.49˚C, an increase of nearly 0.3˚C from April and trending toward NIWA’s El Niño threshold of 0.7˚C.
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    Island Climate Update 271 - May 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the beginning of May was 0.21˚C, in the neutral range, but gradually warming.
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    Island Climate Update 270 - April 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of March was -0.01˚C, in the neutral range for the second consecutive month.
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    Island Climate Update 269 - March 2023

    The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of February was -0.47˚C, in neutral territory for the first time since July-August 2022.
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    Island Climate Update 268 - February 2023

    The NINO3.4 Index anomaly (in the central equatorial Pacific) over the last month was -0.69˚C, close to La Niña thresholds.
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    Island Climate Update 267 - January 2023

    The NINO3.4 Index anomaly (in the central equatorial Pacific) over the last month was -0.83˚C (climatology: 1991-2020), showing a slight warming trend compared to November.
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    Island Climate Update 266 - December 2022

    The NINO3.4 Index anomaly (in the central equatorial Pacific) over the last month was 0.92˚C (climatology: 1991 2020), showing a cooling trend compared to October.
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    Island Climate Update 265 - November 2022

    The NINO3.4 Index anomaly (in the central equatorial Pacific) over the last month was -0.80˚C (climatology: 1991-2020), in the La Niña range for the third consecutive month.