Seasonal Forecast for April – June 2025
Updated 3 April 2025
The Northeast Monsoon persisted in March 2025, characterized by the prevailing northwesterly or northeasterly winds over the ASEAN region. The Northeast Monsoon is expected to transition into inter-monsoon conditions during the first half of April 2025, characterised by light winds that are variable in direction. During the inter-monsoon period, while occasional isolated showers occur over some parts of the Mekong sub-region , most of the sub-region continues experiencing its traditional dry season. For the southern ASEAN region, typically isolated to widespread showers occur, with short periods of relatively drier conditions over parts of the region. Typically from the end of May onwards, the prevailing winds gradually transition from light and variable to mainly southeast to southwest as the inter-monsoon period gives way to the Southwest Monsoon, along with the start of the dry season for parts of the southern ASEAN region.
For April 2025 as well as for April to June (AMJ) 2025 period overall, models predict an increased chance of above-normal rainfall over the northern ASEAN region and southeastern Maritime Continent, with below-normal rainfall over the western equatorial region. La Niña conditions are likely transition to neutral, with ENSO neutral conditions predicted from May onwards. The Indian Ocean Dipole (IOD) is currently neutral. Above-normal temperature is predicted for much of the ASEAN region for AMJ 2025. The effect of La Niña conditions may still be present for a while after its decay, in particular, La Niña tends to moderate temperatures for much of the region at this time of year.
While occasional showers are expected over the northern ASEAN region during the start of the outlook period, elevated hotspot activity and widespread transboundary haze are likely to remain over many parts of the Mekong sub-region until the second half of April 2025, before gradually improving when wetter conditions return to most parts of the sub-region during the onset of the inter-monsoon period. Over the southern ASEAN region, an increase in hotspot activity with localised smoke plumes may be expected over areas experiencing below-normal rainfall. As the region experiences drier conditions with the onset of the Southwest Monsoon, the hotspot and smoke haze situation may gradually elevate.
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 April 2025, above-normal rainfall is predicted for much of the northern ASEAN region and southeastern Maritime Continent, with below-normal rainfall predicted over the western equatorial region.
For April 2025, above-normal rainfall is predicted for much of the northern ASEAN region and southeastern Maritime Continent based on the multi-model ensemble (Figure 4). For the northern ASEAN region, the UK Met Office model (Figure 3) shows the highest confidence of the above-normal rainfall over central and southern Mainland Southeast Asia and the Philippines, followed by the ECMWF model (Figure 2), and the NCEP model (Figure 1).For the southeastern Maritime Continent, the ECMWF and UK Met Office models show high confidence of above-normal rainfall. For above-normal rainfall over the northern ASEAN region, models’ skill is moderate to good for the ECMWF and UK Met Office models, and low to moderate for the NCEP model. The model skill for above-normal rainfall over southeastern Maritime continent is low to moderate for the ECMWF and UK Met Office models and low for the NCEP model.
Below-normal rainfall is predicted over parts of the western equatorial region, based on the multi-model ensemble (Figure 4). The NCEP model (Figure 1) predicts below-normal rainfall over these regions with highest likelihood and extent, followed by the UK Met Office model (Figure 3) and the ECMWF (Figure 2). The models’ skill is generally low to moderate for the below-normal rainfall for the central equatorial region.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for April 2025 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for April 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for April 2025 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for April 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological rainfall’s lower tercile boundary for March based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for March based on CHIRPS (reference period: 1991-2020). |
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 AMJ 2025, above-normal rainfall is predicted for the northern ASEAN region and southeastern Maritime Continent, with below-normal rainfall predicted for the western equatorial region.
For AMJ 2025, near to above-normal rainfall is predicted for much of the northern ASEAN region and southeastern Maritime Continent based on the multi-model ensemble (Figure 4). While the UK Met Office and ECMWF models (Figure 3 and 2) show relatively higher confidence of above-normal rainfall over much of the eastern parts of the Maritime Continent, the NCEP model (Figure 1) predict a mix of below- to above-normal rainfall for the region. For Mainland Southeast Asia, the UK Met Office model predict the largest extent of above-normal rainfall, with the NCEP and ECMWF models predicting a mix of near- to above-normal rainfall. Models’ skill is generally moderate to good for above-normal rainfall over the northern ASEAN region and the southeastern Maritime Continent.
Below-normal rainfall is predicted over the western half of the equatorial region, based on the multi-model ensemble (Figure 4). The NCEP model (Figure 1) predicts below-normal rainfall over this region with highest likelihood and largest extent (stretching across the whole region), followed by the ECMWF model (Figure 2) with below-normal rainfall predicted over the western half, while the UK Met Office model (Figure 3) predicts below-normal rainfall only over the western most region. The models’ skill for below-normal rainfall is low to moderate over this region.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for AMJ 2025 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for AMJ 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for AMJ 2025 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for AMJ 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological rainfall’s lower tercile boundary for AMJ based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for AMJ based on CHIRPS (reference period: 1991-2020). |
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 April 2025, above-normal temperature is predicted over much of the ASEAN region.
For April 2025, above-normal temperature is predicted over much of the ASEAN region based on the multi-model ensemble (Figure 4), except over central and eastern parts of Mainland Southeast Asia with near-normal temperature predicted. The above-normal temperature over the southern ASEAN region is predicted with highest confidence by the ECMWF model (Figure 2) followed by the UK Met Office model (Figure 3) and the NCEP model (Figure 1). Models’ skill for predicting above-normal temperature is good over the Maritime Continent as well as over much of Mainland Southeast Asia, except over northern Mainland Southeast Asia with generally moderate skill. Models’ skill for predicting near-normal temperature is low to moderate for the mentioned regions.
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| Figure 1: Temperature tercile summary predictions of NCEP model for April 2025 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for April 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for April 2025 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for April 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for April based on ERA5 (reference period: 1991-2020). |
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 AMJ 2025, the models predict an increased chance of above-normal temperature over much of the ASEAN region.
For AMJ 2025, above-normal temperature is predicted over much of the ASEAN region based on the multi-model ensemble (Figure 4), with near-normal temperature predicted over much of central and eastern Mainland Southeast Asia. All three models agree with high confidence on above-normal temperature over most of the Maritime Continent. For Mainland Southeast Asia, the near-normal temperature over the central and eastern regions are predicted with largest extent by the UK Met Office model (Figure 3), followed by the ECMWF model (Figure 2) and then the NCEP model (Figure 1). Models’ skill for predicting above-normal temperature is good over most of these regions, and moderate for near-normal temperature for the mentioned regions.
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| Figure 1: Temperature tercile summary predictions of NCEP model for AMJ 2025 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for AMJ 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for AMJ 2025 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for AMJ 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for AMJ based on ERA5 (reference period: 1991-2020). |
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.