Review of Regional Weather Conditions for First Fortnight of June 2019
1. Review of Regional Weather Conditions for First Fortnight of June 2019
1.1 In the first fortnight of June 2019, strong southwesterly winds prevailed over the northern parts of Lao PDR and Viet Nam while anomalous easterly winds or southeasterly winds were observed elsewhere in the northern ASEAN region. In the southern ASEAN region, southeasterly winds prevailed (Figure 1).
Figure 1: 5000 ft average winds (left) and anomalies (right) for 1 – 15 June 2019. (Source: JMA)
1.2 There were isolated showers over many parts of the northern ASEAN region, while scattered showers fell over coastal Myanmar. Above-average rainfall was received in northern and southern Viet Nam, eastern half of Cambodia, and parts of northern Lao PDR. Below-average to near-average rainfall was received elsewhere in the northern ASEAN region. In the southern ASEAN region, above-average rainfall was received near the equator, in particular over Malaysia, Sulawesi, central Sumatra, and most parts of Kalimantan. Below-average rainfall was recorded mainly around Java and the Timor Sea regions.
Figure 2: Daily average rainfall for the ASEAN region in the first fortnight of June 2019. (Source: JAXA Global Satellite Mapping of Precipitation)
Figure 3: Percent of average rainfall for 1 – 15 June 2019. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)
1.3 During the first week of June 2019, the Madden-Julian Oscillation (MJO) propagated through Phases 2 and 3. The MJO signal weakened briefly before strengthening again and propagating through Phase 4. The MJO signal in these phases typically bring wetter conditions over the equatorial parts of the ASEAN region, and its influence in early June 2019 may have been a contributing factor to the wetter-than-usual conditions experienced in the equatorial southern ASEAN region.
1.4 The sea-surface temperatures (SST) were warmer than average over the Nino3.4 region during the first fortnight of June 2019. However, trade winds were close to normal over the equatorial Pacific Ocean. Neither El Nino nor La Nina conditions prevailed during the period.
Figure 4: The MJO phase diagram for June 2019 (blue). The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator. The distance of the index from the centre of the diagram is correlated with the strength of MJO. When the index falls within the circle, the MJO is generally considered weak or indiscernible. (Source: Bureau of Meteorology)
Review of Land Fires and Smoke Haze Situation for First Fortnight of June 2019
Review of Land Fires and Smoke Haze Situation for First Fortnight of June 2019
1.1 Hotspot activities in the ASEAN region were generally subdued. On occasions, isolated hotspots were detected in a few parts of the region.
Figure 1: Himawari-8 satellite image on 10 June 2019 shows a localised smoke plume in Pahang, Peninsular Malaysia.
June 12, 2019
Outlook for Land Fires and Smoke Haze Situation (16 – 30 June 2019)
Outlook for Land Fires and Smoke Haze Situation (16 – 30 Jun 2019)
Issued 12 June 2019
Hotspot activities in the northern ASEAN region are expected to remain mostly subdued. In the southern ASEAN region, occasional hotspot activities with localised smoke plumes may emerge in the fire-prone provinces of Sumatra and Kalimantan during periods of dry weather.
Subseasonal Weather Outlook (16- 30 June 2019)
Subseasonal Weather Outlook (16 – 30 June 2019)
Issued 12 June 2019
Valid for weeks 3 and 4: 16 June – 30 June
Wetter than usual conditions are forecast over the southern parts of Myanmar, Thailand and Viet Nam, as well as over Cambodia in the second fortnight of June 2019. In the southern ASEAN region, the drier than usual conditions observed over Java Sea areas during the first fortnight are expected to persist and spread to the north and east towards Sulawesi and Papua.
The current weak MJO signal is expected to strengthen slightly and propagate eastwards through Phase 4 and Phase 5. This is expected to bring wetter than usual conditions over the southern parts of the Mekong Sub-region. Most models predict the MJO signal to decay towards the end of the month.
The warm conditions over the northern ASEAN region are expected to persist, particularly for inland areas.
The 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.
Review of Regional Weather Conditions for Second Fortnight of May 2019
Review of Regional Weather Conditions for Second Fortnight of May 2019
1. Review of Regional Weather Conditions for Second Fortnight of May 2019
1.1 In the second fortnight of May 2019, prevailing winds were mostly from the southwest or west over the northern ASEAN region. In the southern ASEAN region, winds were generally weak and variable in direction over the equatorial region, but moderate to strong south-easterly winds prevailed over the Java Sea and Banda Sea areas.
Figure 1: 5000 ft average winds (left) and anomalies (right) for 16 – 31 May 2019. (Source: JMA)
1.2 In the second half of May 2019, there were shower activities on most days over many parts of the ASEAN region except over the Java Sea area where dry weather prevailed. This was brought about by the incursion of dry continental air mass from Australia, transported by the anomalously strong south-easterly winds over the Java Sea during the review period. Below-average rainfall was also observed in southern Sumatra, parts of Kalimantan, northern Myanmar and eastern Thailand.
1.3 The Madden-Julian Oscillation (MJO) propagated through Phases 8 – 1, and this could have contributed to the drier-than-average conditions over the Java Sea area. The MJO contributed to large-scale wind anomalies over the Indian Ocean and the Java Sea. Toward the end of May, the MJO reached the Indian Ocean (Phase 2).
Figure 2: Daily average rainfall for the ASEAN region in the Second Fortnight of May 2019. (Source: JAXA Global Satellite Mapping of Precipitation)
Figure 3: Percent of average rainfall for 16 – 31 May 2019. The rainfall data may be less representative for areas with a less dense rainfall network. Hatched areas indicate climatology dry mask (average daily rainfall below 1 mm). (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)
1.4 Slightly warm sea-surface temperature (SST) anomalies over the Nino3.4 region were still observed. There was a slight weakening of the trade winds in the eastern Pacific Ocean towards the end of May 2019. Overall, there were no clear indications of El Nino conditions as the coupling of the SST and atmosphere over the tropical Pacific remained inconsistent.
Figure 4: The MJO phase diagram for April 2019-May 2019 (green for May). The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator. The distance of the index from the centre of the diagram is correlated with the strength of MJO. When the index falls within the circle, the MJO is considered weak or indiscernible. (Source: Bureau of Meteorology)
Review of Land Fires and Smoke Haze Situation for Second Fortnight of May 2019
Review of Land Fires and Smoke Haze Situation for Second Fortnight of May 2019
1.1 In the second half of May 2019, the increase of shower activities over the Mekong sub-region brought a further improvement to the hotspot and haze situation. There were still some isolated hotspot activities but these were gradually subsequently subdued by the rainy weather.
1.2 In the southern ASEAN region, occasional dry weather led to the emergence of isolated hotspots with smoke plumes in Riau, Sumatra, Peninsular Malaysia and West Kalimantan. However, these hotspot activities were short-lived and were subsequently subdued by shower activities.
Figure 1: Himawari-8 satellite image on 26 May 2019 shows isolated hotspots with localised smoke plumes in Peninsular Malaysia and Riau, Sumatra.
June 3, 2019
Subseasonal Weather Outlook (1- 15 June 2019)
Subseasonal Weather Outlook (1 – 15 June 2019)
Issued 3 June 2019
Valid for weeks 1 and 2: 3 June – 15 June
For the first half of June 2019, drier than average conditions are expected to persist over Myanmar.
For the rest of the northern ASEAN region, the prevailing drier than average conditions are likely to ease.
During the forecast period, the MJO that is currently active in the western hemisphere and Africa is forecast to propagate eastwards over the Indian Ocean. The presence of the MJO in Week 1 may bring wetter than average conditions over parts of the equatorial ASEAN region, including Sumatra, southern Peninsular Malaysia and south-western Borneo. However, drier than average conditions conditions can be expected over the areas surrounding Java Sea and Banda Sea.
Warm conditions are expected to continue over most of the northern ASEAN region.
The 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.
Outlook for Land Fires and Smoke Haze Situation (1 – 15 June 2019)
Outlook for Land Fires and Smoke Haze Situation (1 – 15 Jun 2019)
Issued 3 June 2019
Hotspot activities in the ASEAN region are likely to remain mostly subdued. Nonetheless, isolated hotspots with localised smoke plumes may still emerge during occasional periods of drier weather.