Seasonal Forecast for December, January, February 2018-2019

Updated 10 December 2018

Summary of Outlook

Northeast Monsoon conditions over the ASEAN region has led to the onset of the dry season over the northern ASEAN region and the rainy season over the southern ASEAN region.

During the dry season, extended periods of dry weather can be expected over the northern ASEAN region. While in the southern ASEAN region, rainy conditions can be expected but parts of the equatorial ASEAN region including Malaysia, Sumatra and Kalimantan may experience occasional dry weather in February 2019.

During the Dec-Jan-Feb 2019 season, above-normal temperatures are likely over many parts of the ASEAN region, especially over the area around Sumatra and Peninsular Malaysia.

In terms of rainfall, below-normal conditions are forecast over much of the Philippines. Elsewhere, the trend is unclear.

The dry season over the northern ASEAN region is likely to lead to an increase in hotspot activities. In the southern ASEAN region, hotspot activities are likely to remain subdued due to the rainy weather. However, occasional hotspots may still emerge in the fire-prone areas of Sumatra and Kalimantan during brief periods of dry weather.

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 December 2018, below-normal rainfall is expected over much of the Philippines, while above normal rainfall is expected over the western equatorial region. Elsewhere, climatological probabilities are generally predicted.

 
For December’s rainfall, all three models – NCEP CFSv2, ECMWF, and the UK Met Office (Figures 1a-c) predict below-normal rainfall over much of the Philippines. For the southernmost part of the region, NCEP CFSv2 predicts below-normal rainfall over eastern Java and Sulawesi, with ECMWF and UK Met Office models shifting the below-normal rainfall further to the west, only covering Java. The disagreement between the models indicates a lower confidence in the below-normal rainfall for this region compared to over the Philippines.

For parts of Sumatra, southern Malay Peninsula and western Borneo, all three models predict an increase likelihood of above-normal rainfall, with the NCEP and the UK Met Office models indicating a higher probability compared to the ECMWF model. However, there is only moderate skill for this region in December. Elsewhere, climatological probabilities are predicted.

Overall, the models’ skill for rainfall are very good for the eastern and southern ASEAN region, the Philippines, with low to moderate skill elsewhere (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office”).

Rainfall Tercile Summary of NCEP model.

Figure 1a: Rainfall tercile summary predictions of NCEP model for December 2018.

Rainfall Tercile Summary of ECMWF model.

Rainfall Tercile Summary of Met Office model.

Figure 1b: Rainfall tercile summary predictions of ECMWF model for December 2018 (contains modified Copernicus C3S information). Figure 1c: Rainfall tercile summary predictions of UK Met Office model for December 2018 (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 2018/19, below-normal is favoured over much of the Philippines as well as parts of Myanmar and Thailand. The three models referred to here show little agreement for the rest of the ASEAN region.

 
For DJF 2018/2019, all three models – NCEP CFSv2, ECMWF, and UK Met Office (Figures 2a-c) predict below-normal over the Philippines, southern Thailand, and parts of Myanmar and southern Vietnam. All three models have generally good skill (NCEP, ECMWF, UK Met Office) over the Philippines with low to moderate skill elsewhere.

Assessing model predictions elsewhere, the NCEP CFSv2 model predicts above-normal rainfall over Sumatra, as well as parts of Borneo, the Malay Peninsula, Thailand, Laos, northern Vietnam, and eastern Indonesia. However, the ECMWF and UK Met Office models generally predict below-normal to near-normal rainfall for these regions, apart from eastern Indonesia, Borneo and northern Vietnam, where the UK Met Office predicts above-normal rainfall.

Rainfall Tercile Summary of NCEP model.

Figure 2a: Rainfall tercile summary predictions of NCEP model for DJF 2018-2019.

Rainfall anomaly of ECMWF model.

Rainfall Tercile Summary of Met Office model.

Figure 2b: Rainfall tercile summary predictions of ECMWF model for DJF 2018-2019 (contains modified Copernicus C3S information). Figure 2c: Rainfall tercile summary predictions of UK Met Office model for DJF 2018-2019 (contains modified Copernicus C3S information).

The qualitative outlook is assessed for the region in general, and based on the latest run from models provided by the SEA-RCC LRF node. 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 2018, above-normal temperature is favoured over many parts of Southeast Asia.

 
All three models – NCEP CFSv2, ECMWF, and UK Met Office (Figures 1a-c) provide a consistent outlook for above-normal temperature over most parts of the ASEAN region, except for parts of Myanmar, northern Laos, northern Vietnam, and the Philippines. For these four regions, temperature is predicted to be near-normal to above-normal. Overall, the magnitude of the likelihood for above-normal temperature is higher for NCEP CFSv2 than the ECMWF and the UK Met Office models, consistent with previous months’ outlooks.

Over land across the region, the models’ skill for temperature prediction are generally very good (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 December 2018. Figure 1b: Temperature tercile summary predictions of ECMWF model for December 2018 (contains modified Copernicus C3S information).

Temperature Tercile Summary of Met Office model.

Figure 1c: Temperature tercile summary predictions of UK Met Office model for December 2018 (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 2018/19, above-normal temperature is favoured over most of Southeast Asia.

 
For the DJF 2018/19, all three models – NCEP CFSv2, ECMWF, and UK Met Office (Figures 2 a-c) favour above-normal temperature conditions over most of the region with the highest likelihood over the western equatorial region.

Over land across the region, the models’ skill for temperature prediction are generally very good (see the respective sections of “Model products and verification: NCEP, ECMWF, UK Met Office”).

Temperature Tercile Summary of NCEP model.

Figure 2a: Temperature tercile summary predictions of NCEP model for DJF 2018-2019.

Temperature Tercile Summary of ECMWF model.

Temperature Tercile Summary of Met Office model.

Figure 2b: Temperature tercile summary predictions of ECMWF model for DJF 2018-2019 (contains modified Copernicus C3S information). Figure 2c: Temperature tercile summary predictions of UK Met Office model for DJF 2018-2019 (contains modified Copernicus C3S information).

The qualitative outlook is assessed for the region in general, and based on the latest run from models provided by the SEA-RCC LRF node. 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.