Seasonal Forecast for October-November-December 2019

Updated 30 September 2019

Summary of Outlook

The Southwest Monsoon season is expected to transition to the inter-monsoon period in early October 2019. Inter-monsoon conditions are characterised by light and variable winds and rainy conditions over many parts of the ASEAN region. The inter-monsoon period may persist for several weeks before giving way to the Northeast Monsoon season in late November/early December. During the Northeast Monsoon season, the prevailing winds typically blow from the northwest or northeast over most parts of the region. The northern ASEAN region enters its traditional dry season while the southern ASEAN region can expect rainy weather.

For the last quarter of year 2019, most parts of the southern ASEAN region are expected to receive below-normal rainfall. Warmer conditions are also likely to prevail over much of the ASEAN region, except for some coastal areas to the south of the Equator, where near-normal or below-normal temperatures are expected.

The increase in shower activities over the southern ASEAN region arising from the transition to inter-monsoon conditions and later to the Northeast Monsoon is expected to help improve the hotspot and haze situation.

In the northern ASEAN region, hotspot activities are expected to be generally subdued during the inter-monsoon period. With warmer conditions predicted, a gradual escalation of hotspot activities can be expected following the onset of the Northeast Monsoon season towards the end of the year.

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.

For October 2019, below-normal rainfall is favoured over most of equatorial and southern Southeast Asia. Elsewhere, predictions either are not consistent across models, or have less skill.

 

For October 2019, all three models – NCEP CFSv2, ECMWF and the UK Met Office (Figures 1a-c) – continue predicting an increased chance of below-normal rainfall for most parts of equatorial and southern Southeast Asia. The skill is generally highest south of the Equator where all three models tend to have moderate to high skill. North of the equator (0-10°N), however, the models have only low to moderate skill.

For northern Southeast Asia, the three models differ in their predictions. For example, in most parts of Myanmar, both the NCEP CFSv2 and UK Met Office models predicted above-normal rainfall while no dominant conditions are predicted by ECMWF model. Notwithstanding, model skill for October over land in this part of the region is generally poor (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office”).

Rainfall Tercile Summary of NCEP model.

Rainfall Tercile Summary of ECMWF model.

Figure 1a: Rainfall tercile summary predictions of NCEP model for October 2019. Figure 1b: Rainfall tercile summary predictions of ECMWF model for October 2019 (contains modified Copernicus C3S information).

Rainfall Tercile Summary of UK Met Office model.

Rainfall Tercile Summary of MME model.

Figure 1c: Rainfall tercile summary predictions of UK Met Office model for October 2019 (contains modified Copernicus C3S information). Figure 1d: Rainfall tercile summary predictions of multi-model ensemble model for October 2019 (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 OND 2019, below-normal rainfall is favoured over most of the southern Southeast Asia.

 

For OND 2019, all three models – NCEP CFSv2, ECMWF and the UK Met Office (Figures 2a-c) predict below-normal rainfall over most of the southern Southeast Asia. The likelihood for below-normal tercile varies among the models, with the NCEP (Figure 2a) model showing higher probabilities than the ECMWF (Figure 2b) and UK Met Office (Figure 2c) models. Overall, the models’ skill scores for rainfall are relatively good over this region except for northern parts of Sumatra and Borneo.

There is no consistent prediction for much of northern Southeast Asia, although there is increased likelihood for above-normal rainfall for select regions (e.g. Myanmar and northern parts of Laos and Vietnam). Models’ skill scores for this region are also generally low for the OND season (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office“).

Rainfall Tercile Summary of NCEP model.

Rainfall Tercile Summary of ECMWF model.

Figure 2a: Rainfall tercile summary predictions of NCEP model for OND 2019. Figure 2b: Rainfall tercile summary predictions of ECMWF model for OND 2019 (contains modified Copernicus C3S information).

Rainfall Tercile Summary of UK Met Office model.

Rainfall Tercile Summary of MME model.

Figure 2c: Rainfall tercile summary predictions of UK Met Office model for OND 2019 (contains modified Copernicus C3S information). Figure 2d: Rainfall tercile summary predictions of multi-model ensemble model for OND 2019 (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 October 2019, above-normal temperature is favoured over most parts of Southeast Asia north of the equator, except for the southern Maritime Continent where below- or near-normal temperature is predicted over the ocean and coastal regions.

 

For October 2019, all three models – NCEP CFSv2, ECMWF, and UK Met Office (Figures 1a-c) – consistently predict above-normal temperature conditions over most parts of Southeast Asia north of the equator with stronger probabilities over regions between 0-10°N. For the southern parts of the Maritime Continent, in particular over the ocean and coastal regions, all three models predict below- or near-normal temperature conditions.

The models’ skill scores for predicting both above- and below-normal temperature terciles are generally good over equatorial parts of Southeast Asia except for the southern Maritime Continent (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office”).

Temperature tercile Summary of NCEP model.

Temperature tercile Summary of ECMWF model.

Figure 1a: Temperature tercile summary predictions of NCEP model for October 2019. Figure 1b: Temperature tercile summary predictions of ECMWF model for October 2019 (contains modified Copernicus C3S information).

Temperature tercile Summary of UK Met Office model.

Temperature tercile Summary of MME model.

Figure 1c: Temperature tercile summary predictions of UK Met Office model for October 2019 (contains modified Copernicus C3S information). Figure 1d: Temperature tercile summary predictions of multi-model ensemble model for October 2019 (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 OND 2019, above-normal temperature is favoured for most parts of Southeast Asia except for the southern Maritime Continent where below- or near-normal temperature is predicted over the ocean and coastal regions.

 

For OND 2019, all three models – NCEP CFSv2, ECMWF, and UK Met Office (Figures 2 a-c) – favour above-normal temperature over most parts of the region except for the southern Maritime Continent, where below- or near-normal temperature is predicted over the ocean and coastal regions.

The models’ skill for OND temperature prediction is good overall, for both below-normal and above-normal terciles (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office”).

Temperature tercile Summary of NCEP model.

Temperature tercile Summary of ECMWF model.

Figure 2a: Temperature tercile summary predictions of NCEP model for OND 2019. Figure 2b: Temperature tercile summary predictions of ECMWF model for OND 2019 (contains modified Copernicus C3S information).

Temperature tercile Summary of UK Met Office model.

Temperature tercile Summary of MME model.

Figure 2c: Temperature tercile summary predictions of UK Met Office model for OND 2019 (contains modified Copernicus C3S information). Figure 2d: Temperature tercile summary predictions of multi-model ensemble model for OND 2019 (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.