Seasonal Forecast for November 2024 – January 2025
Updated 4 November 2024
The Southwest Monsoon had gradually transitioned into the inter-monsoon period during October 2024. Climatologically, the inter-monsoon conditions are likely to persist over the ASEAN region in November. During this period, prevailing winds are typically light and variable in direction across most of the region. With the monsoon rain band located close to the Equator, increase in shower activities can be expected over the equatorial ASEAN region. The gradual onset of the Northeast Monsoon typically occurs in December, characterised by prevailing winds blowing predominantly from the northeast.
For the November 2024 to January 2025 (NDJ) period, near- to above-normal rainfall is predicted for much of the southern and eastern Maritime Continent. La Niña conditions are likely during November 2024 – February 2025. While there are signs of a negative Indian Ocean Dipole in October 2024, these conditions are predicted to be short lived and predicted to return to neutral by December 2024. Both La Niña and negative IOD events tend to bring wetter than average rainfall to parts of the ASEAN region. Above-normal temperature is predicted for much of the ASEAN region for NDJ 2024-2025.
Over the southern ASEAN region, the dry season ended in October 2024. During the outlook period, the overall hotspot activity in the region is expected to remain subdued. However, isolated hotspots with smoke plumes may still occur over areas experiencing periods of drier conditions. As the traditional dry season for the northern ASEAN region sets in with the onset of the Northeast Monsoon in December, the hotspot and smoke haze activity is expected to progressively intensify over the fire-prone areas of the Mekong sub-region, particularly over areas where below-normal rainfall is expected.
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 November 2024, above-normal rainfall is predicted over much of the Maritime Continent.
For November 2024, above-normal rainfall is predicted over much of the Maritime Continent, based on the multi-model ensemble (Figure 4), with the exception over the western Maritime Continent where a mix of below- to above-normal rainfall is predicted. For above-normal rainfall in the Maritime Continent, the UK Met Office model (Figure 3) shows the highest confidence for the southern region, while the NCEP model shows the highest confidence for the northeastern region. The models’ skill for the Maritime Continent region is moderate to good for predicting above-normal rainfall for much of the region, with low to moderate for predicting rainfall over the western Maritime Continent.
For Mainland Southeast Asia, above-normal rainfall is predicted over the southeastern coastal region and below-normal rainfall is predicted over the central and northeastern regions, with no dominant tercile elsewhere, based on the multi-model ensemble (Figure 4). All three models predict above-normal rainfall over the southeastern coastal region. Elsewhere, the ECMWF and UK Met Office models (Figures 2 and 3) predict below-normal rainfall for much of the rest of the region, while the NCEP model predict below-normal rainfall just for the northeastern part. Model skill is generally low to moderate for Mainland Southeast Asia region at this time of the year, except for predicting above-normal rainfall over the southeastern coastal region where model skill is moderate to high.
|
|
| Figure 1: Rainfall tercile summary predictions of NCEP model for November 2024 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for November 2024 (contains modified Copernicus C3S information). |
|
|
| Figure 3: Rainfall tercile summary predictions of UK Met Office model for November 2024 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for November 2024 (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological rainfall’s lower tercile boundary for November based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for November 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 NDJ 2024-2025, above-normal rainfall is predicted for much of the southern and eastern Maritime Continent.
For NDJ 2024-2025, above-normal rainfall is predicted for the southern and eastern Maritime Continent with below-normal rainfall over parts of the western half of the equatorial region, based on the multi-model ensemble (Figure 4). All three models (NCEP, ECMWF, and the UK Met Office, Figures 1 – 3), predict above-normal rainfall over the southern and eastern Maritime Continent, with the UK Met Office model shows the highest likelihood. There is disagreement among the models for the rest of the Maritime Continent, with NCEP model predicting below-normal rainfall, ECMWF model predicting mix of below- to above-normal rainfall, while the UK Met Office model predicting near- to above-normal rainfall. Model skill is relatively good for above-normal rainfall over much of the Maritime Continent, and low for the western Maritime Continent.
For Mainland Southeast Asia, above-normal rainfall is predicted for the southeastern coastal region and below-normal rainfall is predicted for the northeastern region. While the NCEP and UK Met Office models (Figure 1 and 3) agree on the mentioned regions, the ECMWF model (Figure 2) agrees only on above-normal rainfall over the southeastern coastal region. Elsewhere, there is either no dominant tercile or disagreement among the models. The model skill is generally moderate over the eastern coastal region of Mainland Southeast Asia, and low elsewhere.
|
|
| Figure 1: Rainfall tercile summary predictions of NCEP model for NDJ 2024-2025 (contains modified Copernicus C3S information). | Figure 2: Rainfall tercile summary predictions of ECMWF model for NDJ 2024-2025 (contains modified Copernicus C3S information). |
|
|
| Figure 3: Rainfall tercile summary predictions of UK Met Office model for NDJ 2024-2025 (contains modified Copernicus C3S information). | Figure 4: Rainfall tercile summary predictions of multi-model ensemble model for NDJ 2024-2025 (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological rainfall’s lower tercile boundary for NDJ based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for NDJ 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 November 2024, above-normal temperature is predicted over much of the ASEAN region.
For November 2024, above-normal temperature is predicted over much of the ASEAN region based on the multi-model ensemble (Figure 4), with the exception for parts of eastern Mainland Southeast Asia with near-normal temperature predicted. All three models (NCEP, ECMWF, and the UK Met Office) agree with high confidence on above-normal temperature over the Maritime Continent (Figures 1 – 3). For Mainland Southeast Asia, the ECMWF and UK Met Office models predicts above-normal temperature for much of the region with higher likelihood over the northwestern region, while the NCEP model (Figure 1) predict above-normal temperature for the western region and a mix of below- to near-normal temperature for the rest of the region. The model skill is relatively good for predicting above-normal temperature over the southern ASEAN region and moderate to good over most of the northern ASEAN region.
|
|
| Figure 1: Temperature tercile summary predictions of NCEP model for November 2024 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for November 2024 (contains modified Copernicus C3S information). |
|
|
| Figure 3: Temperature tercile summary predictions of UK Met Office model for November 2024 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for November 2024 (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological temperature for November 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 NDJ 2024-2025, near-normal temperature is predicted over-eastern Mainland Southeast Asia, with above-normal temperature predicted elsewhere.
For NDJ 2024-2025, above-normal temperature is predicted for much of the ASEAN region based on the multi-model ensemble, apart from over parts of eastern Mainland Southeast Asia where near-normal temperature is predicted (Figure 4). All three models (NCEP, ECMWF, and the UK Met Office, Figures 1 – 3) agree with high confidence on above-normal temperature over most of the Maritime Continent and western Mainland Southeast Asia. Elsewhere for Mainland Southeast Asia, the ECMWF model predicts above-normal temperature for much of the region, the UK Met Office model predicts a mix of near- and above-normal temperature, while the NCEP model predicts below- to near-normal temperature. The model skill for predicting below- and above-normal temperature for the ASEAN region is relatively good for much of the region, except for northern Mainland Southeast Asia where the model skill is low to moderate.
|
|
| Figure 1: Temperature tercile summary predictions of NCEP model for NDJ 2024-2025 (contains modified Copernicus C3S information). | Figure 2: Temperature tercile summary predictions of ECMWF model for NDJ 2024-2025 (contains modified Copernicus C3S information). |
|
|
| Figure 3: Temperature tercile summary predictions of UK Met Office model for NDJ 2024-2025 (contains modified Copernicus C3S information). | Figure 4: Temperature tercile summary predictions of multi-model ensemble model for NDJ 2024-2025 (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological temperature for NDJ 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.