Seasonal Forecast for December 2023 – February 2024
Updated 02 Dec 2023
The current inter-monsoon conditions over parts of the ASEAN region typically transition to the Northeast Monsoon in December. With the transition to the Northeast Monsoon, prevailing winds over the ASEAN region are likely to strengthen and blow from the northwest or northeast as the monsoon rain band moves south of the Equator.
For the December 2023 to February 2024 (DJF) period, models predict an increased chance of below-normal rainfall over the southern Maritime Continent and parts of the Philippines, and above-normal rainfall over parts of the equatorial region and western parts of Mainland Southeast Asia. The ocean indicators (Nino3.4 index) shows El Niño conditions, with support from key indicators (cloudiness, trade wind). The El Niño conditions are predicted to persist until at least February-March 2024. A positive Indian Ocean Dipole (IOD) has likely reached its peak strength. Models predict the positive IOD to end by January-February 2024. Both El Niño and positive IODs tend to bring drier conditions to much of the region. Above-normal temperature is predicted for most of the ASEAN region for DJF 2023-2024.
The dry season for the southern ASEAN region has ended in November 2023 and the overall hotspot and smoke haze activity for the region is expected to remain subdued during the DJF period. The dry season for the northern ASEAN region is expected to set-in towards the end of the year. While above-normal rainfall is forecast for many parts of Mekong sub-region throughout the forecast period, hotspot and smoke haze activity can still be expected to progressively intensify over the fire-prone areas in the Mekong sub-region. Isolated hotspots and smoke plumes may also occur over parts of the southern ASEAN region experiencing occasional periods of drier weather.
The qualitative outlook is assessed for the region in general and based on the latest runs from models provided by the SEA RCC-Network LRF node. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.
For December 2023, below-normal rainfall is predicted over the southern and eastern Maritime Continent. Above-normal rainfall is predicted around the Malay Peninsula and over parts of Borneo.
For December 2023, below-normal rainfall is predicted over the southern and southeastern Maritime Continent, with highest likelihood over the southwestern Maritime Continent based on the multi-model ensemble (Figure 4). The NCEP model (Figure 1) shows the highest confidence for below-normal rainfall, followed by the ECMWF and the UK Met Office models (Figures 2 and 3). Models’ skill is moderate to good skill for below-normal rainfall over the mentioned regions.
Above-normal rainfall is predicted over central and eastern Mainland Southeast Asia (Figure 4). However, it is the dry season for Mainland Southeast Asia. Above-normal rainfall is also predicted around the Malay Peninsula and over parts of Borneo, based on the multi-model ensemble (Figure 4). The UK Met Office model (Figure 3) has the largest extent and confidence of above-normal rainfall, followed by the ECMWF model (Figure 2) and the NCEP model (Figure 1). Models’ skill for above-normal rainfall is low to moderate for mentioned regions.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for December 2023 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for December 2023 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for December 2023 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for December 2023 (contains modified Copernicus C3S information). |
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for rainfall, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For DJF 2023/2024, models predict an increased chance of below-normal rainfall over the southern Maritime Continent and parts of the Philippines, and above-normal rainfall over parts of the equatorial region.
For DJF 2023/2024, below-normal rainfall is predicted over the southern Maritime Continent and parts of the Philippines, and above-normal rainfall predicted over parts of the equatorial region, based on the multi-model ensemble (Figure 4). The NCEP model (Figure 1) shows the highest confidence for above-normal rainfall, followed by the UK Met Office model (Figure 3) and then the ECMWF model (Figure 2). Models’ skill is moderate to good for below-normal rainfall, and low to moderate for above-normal rainfall for the mentioned region.
For Mainland Southeast Asia, all three models (Figures 1 – 3) agree on above-normal rainfall over the northeastern region. However, it is the dry season for the region and the models’ skill is low to moderate. Elsewhere, there is disagreements between the models and the models’ skill is low for this season.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for DJF 2023/2024 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for DJF 2023/2024 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for DJF 2023/2024 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for DJF 2023/2024 (contains modified Copernicus C3S information). |
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for rainfall, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For December 2023, above-normal temperature is predicted over much of the ASEAN region.
For December 2023, above-normal temperature is predicted over much of the ASEAN region based on the multi-model ensemble (Figure 4). All three models, especially the NCEP and ECMWF models (Figures 1 and 2), agree with high confidence on above-normal temperature over most of the Maritime Continent, and the NCEP and UK Met Office model predict with high confidence of above-normal temperature over Mainland Southeast Asia. The UK Met Office model (Figure 3) predicts below-normal temperature over southeastern tropical Indian Ocean. Models’ skill is moderate to good for predicting below- and above-normal temperature over most of the ASEAN region.
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| Figure 1: Temperature tercile summary predictions of NCEP model for December 2023 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for December 2023 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for December 2023 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for December 2023 (contains modified Copernicus C3S information). |
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for temperature, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For DJF 2023/2024, the models predict an increased chance of above-normal temperature over the ASEAN region.
For DJF 2023/2024, above-normal temperature is predicted for the ASEAN region, based on the multi-model ensemble (Figure 4). All three models agree with high confidence on above-normal temperature over most of the ASEAN region. Models’ skill for predicting above-normal temperature for the ASEAN region is relatively good for much of the region, apart from western half of Mainland Southeast Asia with low to moderate model skill.
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| Figure 1: Temperature tercile summary predictions of NCEP model for DJF 2023/2024 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for DJF 2023/2024 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for DJF 2023/2024 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for DJF 2023/2024 (contains modified Copernicus C3S information). |
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for temperature, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
Frequently Asked Questions
What is a seasonal forecast?
A seasonal forecast provides forecast information about the general weather conditions at seasonal timescales up to several months ahead. Long range predictions rely on predicting components of the atmosphere and the oceans which show variations at large spatial and temporal scales. Among these key components is the sea-surface temperature – an important indicator in the El Niño Southern Oscillation (ENSO) cycle.
Example of probabilistic long range forecast using the multi-model ensemble. For areas nearby Peninsular Malaysia, the forecast is showing a probability of 50-70% of rainfall being in the below-normal (33%) tercile range. (Source: WMO LC LRF)
To account for the chaotic nature of the atmosphere, seasonal forecast adopts a probabilistic approach and the forecast weather condition is presented as an average over an extended period of time, usually with reference to climatology.
ASMC carries out monthly seasonal forecast predictions based on various seasonal model forecasts from the leading meteorological centres, supplemented by individual assessments from respective countries in South East Asia. The skillfulness of seasonal forecast relies greatly on the performance of seasonal models, which differ from one place to another and for different seasons of the year.
Receiver operating characteristic (ROC) score of UK GloSea5 seasonal hindcast for above-normal precipitation scenario for Dec – Feb (left) and May – Jul (right) over Asia region. Higher ROC score (indicated in red) means better model skill. (Source: UK Met Office)
For example, one way to assess the seasonal model skills is to examine the ROC score. From the figures above, we can see that ROC score map differs greatly from one season to another. During the period from Dec to Feb, a high ROC score region is observed mainly over the Philippines whereas during the period from May to Jul, a high ROC score region is observed over the near equatorial region such as Peninsular Malaysia and Sumatra.