Seasonal Forecast for May – July 2022

Updated 29 April 2022

The prevailing inter-monsoon period is expected to persist in May 2022. During this period, the prevailing low-level winds are typically light and variable in direction, and wet weather conditions can be expected over many parts of the ASEAN region as the monsoon rain band is located near the Equator. The inter-monsoon conditions typically transition into the Southwest Monsoon in June and continues throughout July. While this marks the onset of the traditional wet season for the northern ASEAN region, it also signals the start of the traditional dry season for the southern ASEAN region characterised by persistent dry conditions over the region.

For the May to July (MJJ) 2022 period, an increased chance of above-normal rainfall is predicted for much of the southern ASEAN region, apart from below-normal rainfall over the western Maritime Continent. La Niña conditions are present. La Niña conditions are expected to persist through May and likely transition into neutral in June – July 2022. Warmer-than-usual temperature is expected for much of the Maritime Continent, while near-normal temperature is expected over much of Mainland Southeast Asia during MJJ 2022.

The traditional dry season for the northern ASEAN region typically ends in May. In addition, above-normal rainfall expected in the month may further help to alleviate the hotspot and smoke haze situation over the region. In the southern ASEAN region, the hotspot activity is likely to remain generally subdued under wet weather conditions during the inter-monsoon. However, below-normal rainfall is forecast over Peninsular Malaysia as well as northern Sumatra, and hotspots with localised smoke plumes can still be expected in fire-prone areas of the southern ASEAN region during dry periods. As the traditional dry season of the southern ASEAN region sets in during June/July, the hotspot activities over the region are expected to escalate. Despite the above-normal rainfall forecast over most parts of the southern Maritime Continent, the escalation of hotspot activities can still be expected there.

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 May 2022, models predict above-normal rainfall over much of the northern ASEAN region and the southern Maritime Continent.

 

For May 2022, above-normal rainfall is predicted for much of the northern ASEAN region, including central and southern parts of the Philippines, as seen in the multi-model ensemble (Figure 4). Over Mainland Southeast Asia, all three models predict an increased chance of above-normal rainfall over central and eastern parts, with the NCEP model (Figure 1) predicting below- to near-normal rainfall over western Mainland Southeast Asia while the ECMWF and UK Met Office models (Figure 2 and Figure 3) predicting an increased chance in above-normal rainfall. The models’ skill is moderate to relatively good for the Philippines, and southern Mainland Southeast Asia, with low to moderate skill for northern Mainland Southeast Asia.

For the southern ASEAN region, all models predicted an increased chance of above-normal rainfall over southern parts of the Maritime Continent (Figures 1 – 3). However, there is some disagreement between models for the equatorial region, as well as the models’ skill is only low to moderate for this region. The models’ skill is moderate to relatively good for the southern Maritime Continent.

Figure 1a: Rainfall tercile summary predictions of NCEP model for May 2022. Figure 1b: Rainfall tercile summary predictions of ECMWF model for May 2022 (contains modified Copernicus C3S information).

Figure 1c: Rainfall tercile summary predictions of UK Met Office model for May 2022 (contains modified Copernicus C3S information). Figure 1d: Rainfall tercile summary predictions of multi-model ensemble model for May 2022 (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 MJJ 2022, above-normal rainfall is predicted for much of the southern ASEAN region, apart from below-normal rainfall over the western Maritime Continent

 

For MJJ 2022, based on the multi-model ensemble (Figure 4), there is an increased chance of above-normal rainfall for much of the southern ASEAN region, apart from the western Maritime Continent. Among the three models, the NCEP model (Figure 1) and UK Met Office model (Figure 2) predict above-normal rainfall for most of the southern ASEAN region, while the ECMWF model confines the increased chance of above-normal rainfall to the region south of the equator. The models’ skill is moderate to relatively good over the southern ASEAN region.

Over the northern ASEAN region, the model’s skill is low, apart from over the Philippines, where it is moderate. However, there is no dominant predicted tercile for the Philippines in MJJ 2022.

Figure 2a: Rainfall tercile summary predictions of NCEP model for MJJ 2022. Figure 2b: Rainfall tercile summary predictions of ECMWF model for MJJ 2022 (contains modified Copernicus C3S information).

Figure 2c: Rainfall tercile summary predictions of UK Met Office model for MJJ 2022 (contains modified Copernicus C3S information). Figure 2d: Rainfall tercile summary predictions of multi-model ensemble model for MJJ 2022 (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 May 2022, above-normal temperature is favoured over much of the Maritime Continent, with below- to near-normal temperatures over much of Mainland Southeast Asia.

 

For May 2022, above-normal temperature is predicted over much of the Maritime Continent as seen in the multi-model ensemble (Figure 4), with the highest likelihood over the southeastern Maritime Continent. The NCEP model (Figure 1) predicts the highest probability of above-normal temperature for the mentioned regions, followed by the UK Met Office Model (Figure 3) and then the ECMWF model (Figure 2). The models’ skill for the above-normal tercile category for the Maritime Continent is moderate to relatively good.

For Mainland Southeast Asia, the models predict an increased chance of below- to near-normal temperatures for much of the region. The exception is over northern Myanmar where there is an increased chance of above-normal temperature. The model skill is low to moderate for below-normal temperature, and moderate for above-normal temperature for Mainland Southeast Asia.

Figure 3a: Temperature tercile summary predictions of NCEP model for May 2022. Figure 3b: Temperature tercile summary predictions of ECMWF model for May 2022 (contains modified Copernicus C3S information).

Figure 3c: Temperature tercile summary predictions of UK Met Office model for May 2022 (contains modified Copernicus C3S information). Figure 3d: Temperature tercile summary predictions of multi-model ensemble model for May 2022 (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 MJJ 2022, an increased chance of above-normal temperature is predicted over most of the Maritime Continent, while near-normal temperature is predicted over much of Mainland Southeast Asia.

 

For MJJ 2022, all three models – NCEP, ECMWF and UK Met Office (Figures 1-3) – predict an increased chance of above-normal temperature for most of the Maritime Continent, although with a lower chance over the northern Philippines, and parts of Borneo and Java. The model skill for predicting above-normal temperature for the Maritime Continent is relatively good.

For Mainland Southeast Asia, an increased chance of near- normal temperature is predicted by the three models over much of the region, apart from over northern Myanmar. The model skill for this region for below-normal temperature is moderate, and low for near-normal temperature for this season.

Figure 4a: Temperature tercile summary predictions of NCEP model for MJJ 2022. Figure 4b: Temperature tercile summary predictions of ECMWF model for MJJ 2022 (contains modified Copernicus C3S information).

Figure 4c: Temperature tercile summary predictions of UK Met Office model for MJJ 2022 (contains modified Copernicus C3S information). Figure 4d: Temperature tercile summary predictions of multi-model ensemble model for MJJ 2022 (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.