Seasonal Forecast for March – May 2025
Updated 4 March 2025
The Northeast Monsoon which prevailed in recent months, generally persists over the ASEAN region until late March, with the prevailing winds blowing from the northwest or northeast. During this period, the traditional dry season over the northern ASEAN region continues while showers persist over the southern ASEAN region. From late March or early April onwards, the inter-monsoon period typically sets in, characterised by a gradual increase in rainfall over the northern ASEAN region and low-level winds becoming light and variable in direction.
For March 2025, above-normal rainfall is predicted over the northern half of the ASEAN region. For the March to May 2025 (MAM) period overall, above-normal rainfall is predicted over much of Mainland Southeast Asia and the eastern Maritime Continent. La Niña conditions are present, with a transition to ENSO neutral predicted by April-May 2025. La Niña conditions are typically associated with wetter than average conditions over much of Southeast Asia. Near- or above-normal temperature is predicted for the Maritime Continent and western Mainland Southeast Asia.
While above-normal rainfall is predicted for some areas of the Mekong sub-region, elevated hotspots and smoke haze activities, along with a risk of transboundary smoke haze occurrence, may still occur over the areas experiencing prolonged dry conditions. Over the southern ASEAN region, wet weather conditions are expected to prevail, which should keep the overall hotspot and smoke haze situation subdued. However, isolated hotspots with localised smoke plumes may occur during brief dry periods.
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 March 2025, above-normal rainfall is predicted over the northern half of the ASEAN region.
For March 2025, above-normal rainfall is predicted over much of the northern half of the ASEAN region, based on the multi-model ensemble (Figure 4). For the Maritime Continent, the ECMWF and UK Met Office models predict above-normal rainfall over the eastern Maritime Continent with a mix of below- to above-normal rainfall elsewhere, while the NCEP model predicts above-normal rainfall over the northern half of the Maritime Continent and below-normal rainfall for the southern half. Model skill is low to moderate over most of the region, except for over the Philippines where the model skill is overall good.
Over Mainland Southeast Asia, above-normal rainfall is predicted over much of the region, based on the multi-model ensemble (Figure 4), although this is the dry season for this region (Figure 6) and the rainfall anomalies are predicted to be small. For above-normal rainfall over the southeastern parts of Mainland Southeast Asia the model skill is low to moderate.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for March 2025 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for March 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for March 2025 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for March 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 MAM 2025, above-normal rainfall is predicted over much of Mainland Southeast Asia and the eastern Maritime Continent.
For MAM 2025, above-normal rainfall is predicted over much of the eastern Maritime Continent, based on the multi-model ensemble (Figure 4), with below- to near-normal rainfall predicted elsewhere in the Maritime Continent. The ECMWF and UK Met Office models (Figures 2 and 3) predict above-normal rainfall for much of the eastern Maritime Continent, while the NCEP model predicts above-normal rainfall only over the northeastern Maritime Continent. The NCEP model predicts the largest extent of below-normal rainfall over the central Maritime Continent, followed by the UK Met Office model and the ECMWF model. Skill over the northeastern Maritime Continent is relatively good, and low to moderate elsewhere.
For Mainland Southeast Asia, above-normal rainfall is predicted over most of the region, based on the multi-model ensemble (Figure 4). The UK Met Office model predicts an increased chance of above-normal rainfall over most of Mainland Southeast Asia, while the ECMWF predicts above-normal rainfall over the central and southern regions, and the NCEP model predicts above-normal rainfall over parts of western and northern Mainland Southeast Asia. Model skill for above-normal rainfall is relatively good for the southern half of Mainland Southeast Asia and low to moderate elsewhere.
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| Figure 1: Rainfall tercile summary predictions of NCEP model for MAM 2025 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for MAM 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Rainfall tercile summary predictions of UK Met Office model for MAM 2025 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for MAM 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological rainfall’s lower tercile boundary for MAM based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for MAM 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 March 2025, above-normal temperature is predicted for much of the Maritime Continent and the western half of Mainland Southeast Asia.
For March 2025, above-normal temperature is predicted over most parts of the Maritime Continent, except for over the Malay Peninsula and northern half of the Philippines, based on the multi-model ensemble (Figure 4). All three models agree on above-normal temperature over the eastern and central Maritime Continent (Figures 1-3), with the ECMWF and UK Met Office models also predicting above-normal temperature much of the western region. The NCEP model (Figure 1) shows disagreement with other models also over parts of the southwestern Maritime Continent where it predicts near- to above-normal temperature. Model skill is relatively good for the Maritime Continent.
For Mainland Southeast Asia, above-normal temperature is predicted for the western region, based on the multi-model ensemble (Figure 4), with below- to near-normal temperature elsewhere. All three models predict above-normal temperature over the western region, with the NCEP model predicting above-normal temperature also over the eastern half, where the other two models predicting below- to near-normal temperature. Model skill is moderate to good for Mainland Southeast Asia at this time of year.
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| Figure 1: Temperature tercile summary predictions of NCEP model for March 2025 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for March 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for March 2025 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for March 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for March 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 MAM 2025, near- or above-normal temperature is predicted for the Maritime Continent and western Mainland Southeast Asia.
For MAM 2025, above-normal temperature is predicted for the Maritime Continent and western Mainland Southeast Asia, with near-normal temperature predicted for central and eastern Mainland Southeast Asia based on the multi-model ensemble (Figure 4). For the Maritime Continent, all models agree on above-normal temperature for the region, apart from over northern Philippines where the ECMWF and UK Met Office models (Figures 2 and 3) predict above-normal temperature while the NCEP model (Figure 1) predicts near- to above-normal temperature. The ECMWF and UK Met Office models predict near-normal temperature over central and eastern Mainland Southeast Asia while the NCEP model predicts near- to above-normal for the mentioned region. Model skill for above-normal temperature is relatively good for the Maritime Continent and Mainland Southeast Asia. For near-normal temperature over Mainland Southeast Asia, model skill is generally low to moderate.
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| Figure 1: Temperature tercile summary predictions of NCEP model for MAM 2025 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for MAM 2025 (contains modified Copernicus C3S information). |
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| Figure 3: Temperature tercile summary predictions of UK Met Office model for MAM 2025 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for MAM 2025 (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for MAM 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.