Category Archives: Regional Weather Review for Year 2015

1.1    The Northeast Monsoon season prevailed in December 2015 with the monsoon rain in the equatorial region between 5 N and 5 S. In the northern ASEAN region, the dry season onset in mid-December 2015 while scattered shower activities and north-easterly winds affected most parts of the southern ASEAN region including Malaysia, Singapore and Indonesia.

1.2    Typhoon Melor, which developed over the western Pacific Ocean in the second week of December 2015 made landfall over Bulusan in southern Luzon on 14 December 2015. It brought strong winds and heavy rain to the affected areas. Typhoon Melor continued to track westward over the South China Sea before weakening into a tropical depression two days later.

1.3    Likely to be associated with the strong El Niño condition which peaked in December 2015, most of the region experienced drier than usual weather conditions. Above-normal rainfall was received in northern parts of Philippines due to Typhoon Melor, and near-normal rainfall was received in the near-equatorial region, in particularly over Peninsular Malaysia, Singapore, southern Sumatra and western Borneo Island. The regional rainfall distribution for December 2015 is shown in Figure Fig. 1A.

2.1    In the southern ASEAN region, hotspot activities continued to be subdued by shower activities. There were some isolated hotspots detected in Kalimantan in end December 2015.

2.2    There was a gradual escalation of hotspot activities over the northern ASEAN region towards the end of December 2015. In particular, isolated hotspot activities were observed in Thailand and Cambodia. Localised smoke plumes were observed to emanate from some of these hotspots.

3.   Status of El Niño/La Niña

1.1    The Inter-monsoon season, which is characterised by winds that are light and variable in direction and diurnal shower activities, prevailed in November 2015 before transiting into the Northeast Monsoon towards the end of the month. Both the northern and southern ASEAN regions experienced increased shower activities and wet weather conditions prevailed for most parts of the month.

1.2    The El Niño strengthened further in November 2015. However, as the impact of El Niño was usually less significant during the boreal winter season, drier than usual weather conditions were experienced mainly in the Philippines. Near-normal rainfall was received mainly over the northern ASEAN region. Above-normal rainfall was also received in the near-equatorial region especially in parts of Peninsular Malaysia, Sumatra and parts of Borneo island. The regional rainfall distribution for November 2015 is shown in Figure Fig. 1A.

2.1    In the northern ASEAN region, hotspot activities continued to be subdued by shower activities. There were some isolated hotspots detected towards the end of the November 2015 as dry weather conditions in the region started to set in.

2.2    The hotspot activities in the southern ASEAN region eased gradually in November 2015 as increased shower activities over most parts of the region helped to subdue the fires. In particular, the smoke haze in Kalimantan dissipated rapidly in early November 2015 after days of persistent heavy showers over hotspot areas.

2.3    Smoke haze in Sumatra however persisted slightly longer as the showers fell mostly away from the hotspot areas. Moderate smoke haze and scattered hotspots were observed in South Sumatra and these persisted into the second week of November 2015. The haze situation improved rapidly in the second half of November with the occurrence of more showers over the southern ASEAN region. This brought an end to the Southeast Asia smoke haze event that started in late August 2015. Satellite images depicting some of the hotspot activities over the ASEAN region in October 2015 are shown in Figs. 2A to 2E.

Fig. 2E: AQUA satellite picture on 24 November 2015 shows widespread shower activities over the Borneo island.

3.1    The mature El Niño in the tropical Pacific Ocean continues to be at a strong level. The sea-surface temperatures are similar to the 1982-83 and 1997-98 strong El Niño events.

3.2    Atmospheric conditions in the ASEAN region continue to show a clear response to the strong El Niño conditions. Large-scale drier-than-normal conditions have been observed particularly in the southern and eastern parts of the ASEAN region. The consensus forecast based on assessments from international climate models and expert opinion suggests that El Niño conditions to continue through the first quarter of 2016. The strength of El Niño conditions is likely to peak in December 2015 and is expected to gradually decay in 1Q 2016.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially for the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is currently in the Northeast Monsoon season (late Nov – Mar). The impact of El Niño is usually less pronounced during the Northeast Monsoon season as compared to the Southwest Monsoon season (Jun – Sep).

1.1    The Southwest Monsoon conditions continued to prevail for most of October 2015 before giving way to Inter-Monsoon conditions in late-October 2015. In the later part of the month, the monsoon trough migrated southward from northern ASEAN region to the near-equatorial region, of Malaysia, Singapore, Brunei and parts of Indonesia including Sumatra and Kalimantan by end-October.

1.2    Two tropical cyclones affected the ASEAN region in October 2015. Tropical Storm Mujigae, which developed as a weak tropical disturbance near Palau in late September 2015 intensified over the next few days into a Tropical Storm. It made landfall over central Luzon Island in the Philippines on 1O ctober 2015 bringing heavy rainfall and strong winds to the Luzon region before moving over the South China Sea. Tropical Storm Mujigae intensified into a Typhoon on 3 October 2015 and made a second landfall near Hainan Island on 4 October 2015.

1.3    In mid-October 2015, a much more intense tropical cyclone – Tropical Storm Koppu which formed in the western Pacific Ocean intensified into a Super Typhoon as it tracked westwards over the warm waters of the Philippines Sea towards the Philippines. Super Typhoon Koppu made landfall in Aurora province, the Philippines on 17 October 2015. The slow movement of the Typhoon under a weak steering environment resulted in prolonged heavy rain and widespread flooding in Baguio, the Philippines.

1.4    The prevailing strong El Niño conditions continued to suppress rainfall activity over the ASEAN region. Significant drier than usual weather conditions were experienced over large parts of the southern ASEAN region. Near-normal to slightly below-normal rainfall was received in Philippines. Below normal rainfall was also experienced in most parts of the northern ASEAN region. The regional rainfall distribution for October 2015 is shown in Figure Fig. 1A.

2.1    In October 2015, hotspot activities over the northern ASEAN region were subdued by the prevailing wet weather conditions. In the southern ASEAN region, the prolonged dry weather conditions further contributed to the prevailing severe haze situation in Sumatra and Kalimantan. Smoke haze from fires in Sumatra and Kalimantan continued to spread over sea areas by the prevailing winds to affect areas southern ASEAN region as well as southern Philippines, southern Thailand, and Vietnam.

2.2    The fires in South Sumatra and central Kalimantan continued to burn in October 2015 emitting dense smoke haze and reducing visibility to below 1km on many days. In addition, Very Unhealthy/Hazardous air quality readings were reported in Pekan Baru, Jambi and Palembang in Sumatra and Palangkaraya in Kalimantan on most days.

2.3    In the first week of October 2015, smoke haze from Sumatra affected many states along the west coast of Peninsular Malaysia and Singapore while the smoke haze from Kalimantan affected the southern parts of Kuching, Sarawak. During this period, the air quality in these areas deteriorated to Unhealthy levels with several places in Selangor such as Shah Alam, Banting, Port Klang and Putrajaya recorded Very Unhealthy/Hazardous air quality readings on some days.

2.4    An increase of shower activities and a shift of prevailing winds in the region to blow from the east or northeast in the second week of October 2015 brought some temporary respite to the haze situation affecting Peninsular Malaysia, Sarawak and Singapore. The shower activities however were short-lived and fell mostly away from the hostpot areas in Sumatra and Kalimantan. The peatland fires and smoke haze in South Sumatra and Central Kalimantan continued to persist.

2.5    In the second half of October 2015, in particular between 18 and 26 October 2015, the indirect influence of Typhoon Koppu over the Philippines resulted in a shift of the prevailing winds to blow from the southeast or south over the southern ASEAN region. This brought the dry weather conditions back to the region which fuelled the fires that were still raging in the southern parts of Sumatra and Kalimantan.

2.6    The prevailing southeasterly or southerly winds carried moderate to dense smoke haze from Sumatra to many parts of Peninsular Malaysia and Singapore, where API readings in central, southern Peninsular Malaysia and PSI readings in Singapore were mostly in the Unhealthy range between 18-23 October 2015. The smoke haze from Sumatra spread further north as well and affected the northern parts of Sumatra and Malaysia, and southern Thailand. The air quality in the affected areas deteriorated to Unhealthy/Very Unhealthy levels between 21 and 23 October 2015. The 24-hr PM₁₀ concentrations in Penang, Peninsular Malaysia and Songkhla, Thailand reached 383 and 360 ug/m³ respectively on 22 October 2015.

2.7    The smoke haze in Kalimantan continued to thicken as land fires persisted, and on 19 October 2015, widespread thick smoke haze blanketed the southern parts of Kalimantan. PM₁₀ concentrations at Palangkaraya exceeded 1500 ug/m³ on most days during the second half of the month, above the Hazardous level of 420 ug/m³ . Smoke haze from Kalimantan had also spread to the South China Sea and the east coast of Sabah. Some flights to Kota Kinabalu were disrupted or cancelled on 18 October 2015.

2.8    From 27 October 2015 to the rest of the month, a shift in the prevailing winds to blow from the northeast or east and increased shower activities over the areas where the fires were raging brought an improvement to the haze situation in Sumatra and Kalimantan. The showers helped to subdue the hotspot activities in the region and brought a significant improvement to the smoke haze situation in the region. Satellite images depicting some of the hotspot activities over the ASEAN region in October 2015 are shown in Figs. 2A to 2E.

3.1    A strong El Niño prevails in the tropical Pacific Ocean. In October 2015, the sea surface temperatures (SSTs) in the tropical Pacific Ocean (SST) have increased further although the rate of warming has slowed.

3.2    Atmospheric conditions in the ASEAN region are showing a clear response to the strong El Niño conditions. Large-scale drier-than-normal conditions have been observed particularly in the southern and eastern parts of the ASEAN region. A consensus forecast based on international climate models and expert opinion suggests continuation of strong El Niño conditions into early-2016, with the strength of El Niño likely to peak in coming months before decaying.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially in the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is now gradually transitioning from the Inter-Monsoon season (Oct – Nov) into the Northeast Monsoon (Dec – Mar). The impact of El Niño is usually less pronounced during the Northeast Monsoon as compared to the Southwest Monsoon (Jun – Sep).

1.1    The Southwest Monsoon season prevailed in September 2015, with low level winds mainly blowing from the southeast or southwest. The monsoon rain band located close to the northern ASEAN region brought shower activities on most days to parts of the region. In contrast, dry weather conditions in the southern ASEAN region prevailed throughout September 2015.

1.2    Tropical Storm Vamco, which developed on 13 September 2015 over the South China Sea, made landfall south of Danang, Vietnam the next day. Vamco caused flooding and damages particularly to the agriculture and fisheries sectors in Vietnam. The Tropical Storm Vamco continued on its westward track and triggered floods across some provinces in Thailand before gradually dissipating on 18 September.

1.3    The prevailing El Niño conditions continued to have an impact on rainfall activities in the ASEAN region. Below-average rainfall was recorded across most parts of the southern ASEAN region. In the northern ASEAN region, near-average to below-average rainfall was received in the Mekong sub-region. The southern part of Philippines recorded above-average rainfall while below-average rainfall was received in the northern part of Philippines. The regional rainfall distribution for September 2015 is shown in Figure Fig. 1A.

2.1    In September, hotspot activities over the northern ASEAN region were generally subdued by the prevailing wet weather conditions. In contrast, the southern ASEAN region was affected by a prolonged transboundary haze situation in recent years. Persistent hotspot activities were observed especially in the fire-prone provinces of central and southern Sumatra, as well as in Kalimantan throughout the month.

2.2    In September 2015, moderate to dense smoke haze blanketed most parts of the central and southern Sumatra, and West and Central Kalimantan. On most days, the air quality readings in many parts of Sumatra including Jambi were in the hazardous range. Hazardous air quality readings were also reported in Palangkaraya in central Kalimantan and Pontianak in western Kalimantan on a number of days. Visibility was reduced to less than 1 km on most days in Jambi, Pekan Baru and Rengat in Sumatra and in Pontianiak and as the haze situation worsened.

2.3    The moderate to dense smoke haze from the fire-prone provinces in Sumatra and Kalimantan were carried by the prevailing winds to affect the region including Brunei Darussalam, Peninsular Malaysia, Sarawak, Singapore and southern Thailand. Some haze had also spread to the South China Sea and was blown by the prevailing winds to affect some islands in southern Philippines.

2.4    Parts of Peninsular Malaysia, East Malaysia and Singapore were affected by transboundary smoke haze since early September 2015. Air quality was in the Unhealthy and/or Very Unhealthy ranges on most days, and on a few days, the air quality entered into the Hazardous range which resulted in school closures, flight diversions or delayed flights amid poor visibility. On 25 September, the 24-hr PSI in Singapore hit a high of 322. On 26 September, visibility at the Subang Airport deteriorated to below 500 m and the airport was closed for several hours. Air quality readings in Port Klang, Shah Alam and Batu Muda also worsened to Very Unhealthy levels of 224-243 the next day morning.

2.3    In Kuching, Samarahan and Sri Aman, the Air Quality Index (AQI) ranged from ~68-~205, with most days in the Unhealthy to Very Unhealthy range between 9 and 28 September 2015. On 10 September, visibility at the Kuching International Airport deteriorated to below 800m and caused disruptions to flight operations and schedules. Satellite images depicting some of the hotspot activities over the ASEAN region in September 2015 are shown in Figs. 2A to 2E.

3.1    The sea surface temperatures (SSTs) in the tropical Pacific Ocean (SST) have increased further in September 2015. A strong El Niño currently prevails in the tropical Pacific Ocean.

3.2    Atmospheric conditions in the ASEAN region have been showing a clear response to the strong El Niño conditions. Large-scale drier-than-normal conditions have been observed particularly in the southern and eastern parts of the ASEAN region. A consensus forecast based on international climate models and expert opinions suggest the continuation of strong El Niño conditions into early-2016, with the possibility of further strengthening in the coming months.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially in the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is now gradually transitioning from the Southwest Monsoon season (Jun-Sep/Oct) into the inter-monsoon period (Oct Nov). El Niño can still have a significant impact on the weather conditions (dryness) over the southern part of ASEAN region, in particular, the western part of the Maritime Continent. With the current El Niño conditions, there is still a risk that the prevailing Aug-Sep-Oct (ASO) season could experience extended periods of drier and warmer conditions in this part of Southeast Asia.

1.1    The Southwest Monsoon conditions in the region continued to persist in August 2015. In the northern ASEAN region, shower activities prevailed on most days in August 2015. In the southern ASEAN region, the first half of August 2015 experienced wetter than usual weather conditions, in particular around Sumatra, Peninsular Malaysia and Singapore, due to the indirect effects of Super Typhoon Souledor in the northern South China Sea. In the second half of August 2015, dry weather conditions persisted through the period.

1.2    Typhoon Goni, which formed over the western Pacific Ocean near Guam on 14 August, was steered westward towards the Philippines and eventually affected the northern islands of Cagayan province in Luzon Island on 21 August 2015. Typhoon Goni brought strong winds and heavy rains to northern Philippines destroying many homes and displacing many lives along its path. The typhoon clipped through the Philippines and continued on its track northwards before making landfall in the eastern parts of Taiwan on 23 August 2015.

1.3    The prevailing El-Nino conditions continue to bring drier than usual weather conditions over the southern ASEAN region, except in central Sumatra and Peninsular Malaysia where wetter than usual weather conditions were experienced. In the northern ASEAN region, near-average to below-average rainfall was received in the Mekong sub-region. The regional rainfall distribution for August 2015 is shown in Fig. 1A.

2.1    During the review period, hotspot activities in the northern ASEAN region continued to be subdued by shower activities. In contrast, in the southern ASEAN region, following the wet conditions in the first half of the month, a period of extended drier weather contributed to an escalation of hotspot activities for the rest of August 2015. Persistent land and forest fires were observed in central and southern Sumatra, in particular in Jambi and South Sumatra, which lead to widespread moderate to dense smoke haze over many parts of Sumatra.

2.2    Ground observations in Pekan Baru, Jambi and Rengat reported visibility of less than 1 km on several days. In addition, some moderate smoke haze from central Sumatra was observed to spread across the Strait of Malacca to affect Peninsular Malaysia. Several cities along the west coast of Peninsular Malaysia such as Penang and Kuala Lumpur reported low visibilities due to haze and the Air Pollution Index (API) readings were in the high-end of Moderate range.

2.3    In Kalimantan, it was dry with few occurrences of shower activities throughout August 2015. The increased hotspot activities in Kalimantan led to an accumulation of moderate to dense smoke haze especially over western and central Kalimantan. Prevailing southeasterly winds carried the smoke haze towards the northwest to affect Sarawak. On 24 August 2015, there was a deterioration in the air quality in several cities of Sarawak such as Sri Aman and Kuching with the API readings in these cities registering unhealthy levels. In the next few days, the occurrence of showers in Sarawak brought an improvement to the hazy conditions there. Satellite images depicting some of the hotspot activities over the ASEAN region in August 2015 are shown in Figs. 2A to 2E.

3.1    The sea surface temperatures (SSTs) in the tropical Pacific Ocean (SST) have continued to warm in August 2015. A strong El Niño currently prevails in the tropical Pacific Ocean.

3.2    The rainfall in the Southeast Asia region is showing a clear response to the El Niño development, with observed large-scale drier-than-normal conditions, in particular in the southern and eastern parts of the region. A consensus forecast based on international climate models and expert opinion suggests a high likelihood of the warming of the SST to continue. Further strengthening of El Niño conditions are likely in the coming months, and the El Nino is expected to prevail into early 2016.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially for the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The ASEAN region is currently in the Southwest Monsoon season (June-September/early October), where the El Niño is known to have considerable impact (dryness) on the western part of the Maritime Continent. Thus with the current El Niño conditions, there is a high risk that the Sep-Oct-Nov season could experience extended periods of drier and warmer weather conditions in this part of Southeast Asia.

1.1    The Southwest Monsoon conditions in the region continued to prevail in July 2015. While the northern ASEAN region is in its wet season, and the monsoonal rainband continue to lie mostly between latitudes 10 and 15 degrees North, some parts of the region experienced drier than usual conditions. A shift of the monsoon rainband to the near-equatorial region on several days in mid-July 2015 brought shower activities to the southern ASEAN region, in particular over Peninsular and West Malaysia, Sumatra and Kalimantan. Dry weather conditions continue to persist in Java and the eastern archipelago of Indonesia.

1.2    On 5 July 2015, Tropical Storm Linfa made landfall over the northern Luzon Island of the Philippines, bringing heavy rainfall that resulted in floods and landslides in northern Luzon. Linfa continued on its northwestward track into the South China Sea before making landfall in the southern parts of Guangdong province, China.

1.3    Severe drought was experienced in Thailand due to a prolonged drier than usual weather in the months leading up to July. A respite to the drought situation arrived in mid-July 2015 with increased shower activities over Thailand. On the contrary, heavy monsoonal rain bands associated with Cyclone Komen brought widespread flooding to many parts of Myanmar around end-July 2015. More than 260,000 people across 12 of Myanmar’s 14 states were affected by severe floods.

1.4    The southern ASEAN region continued to receive lower than normal rainfall in July which could be partly due to the prevailing El-Nino conditions. For the northern ASEAN region, well-above normal rainfall was received in Myanmar and northern Philippines. Below-normal to near-normal rainfall was received for the rest of the northern ASEAN region. The regional rainfall distribution for July 2015 is shown in Fig. 1A.

2.1    In the northern ASEAN region, shower activities over most parts of the region helped to suppress hotspot activities.

2.2    In the southern ASEAN region, elevated hotspot activities were observed mainly in Riau and Jambi provinces of Sumatra since early-July 2015. Shower activities on several days in mid-July 2015 helped to subdue the hotspot activities. Around end-July 2015, a return of drier weather conditions saw an increase in burning activities, and smoke plumes were seen emanating from various hotspot clusters in Sumatra. Most of the fires were short-lived, and the region was not affected by significant transboundary haze.

2.3    In Kalimantan, there were persistent shower activities in the first half of July 2015. However by mid-July 2015, dry weather conditions emerged and contributed to an increase of hotspot activities in parts of Kalimantan. Moderate haze and smoke plumes were observed near the hotspots for the several days in the second half of July. Satellite images depicting some of the hotspot activities over the ASEAN region in July 2015 are shown in Figs. 2A to 2E.

3.1    The tropical Pacific Ocean’s sea-surface temperature (SST) continues to warm in July 2015. Both its atmosphere and ocean conditions are at moderate El Nino levels.

3.2    The atmospheric patterns over the tropical Pacific Ocean continue to support the El Niño pattern, including weakened trade winds and excess rainfall in the eastern tropical Pacific Ocean. International climate models and expert opinion predict a high likelihood (in excess of 80-90% chance) for this SST warming to continue into early-2016. Further strengthening of the El Niño is likely.

3.3    Typically the impact from El Niño for the Southeast Asia region is drier than average
rainfall conditions, especially for the southern parts during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is now in the Southwest Monsoon season (June – September), where El Niño is known to have considerable impact (dryness) on the western part of the Maritime Continent. Thus with the current El Niño developing conditions, the upcoming Aug-Sep-Oct season faces risk of extended periods of drier and warmer conditions in this part of Southeast Asia.

1.1    The monsoon trough has migrated to the northern ASEAN region, with its position hovered mainly along the 10 N latitude line. The monsoon trough brought persistent shower activities over most parts of northern ASEAN.

1.2    Southwest Monsoon conditions, characterised by low level winds predominantly from the southeast or southwest, onset in the southern ASEAN region from the second half of June 2015. Wet weather conditions prevailed over the region in the first half of June 2015 and transited gradually to drier weather conditions with the onset of the traditional dry Southwest Monsoon season.

1.3    The rainfall over the southern ASEAN region in June has been lower than usual, which can partly be attributed to the prevailing moderate El Niño conditions in the equatorial Pacific Ocean which are likely to further develop in the months ahead. Sumatra, Java and southern Kalimantan received less than 50-75% of the normal rainfall; this is a typical precipitation pattern observed in southern ASEAN during a moderate to strong El Niño event. For the northern ASEAN region, below-normal rainfall has also been recorded in most parts except for central Thailand. The regional rainfall distribution for June 2015 is shown in Fig. 1A.

2.1    In the northern ASEAN region, hotspot activities continued to be subdued by the prevailing wet weather conditions.

2.2    In the southern ASEAN region, increased hotspot activities were detected during the period of drier weather in the second half of June. Persistent hotspots were observed on several days mostly in the provinces of Riau and Jambi in Sumatra. Smoke plumes and moderate haze were seen emanating from these hotspots.

2.3    In June 2015, most parts of Kalimantan were affected by showers. In the second half of June 2015, a period of drier weather led to the occurrence of isolated hotspots with localized smoke plumes in parts of western Kalimantan. Satellite images depicting some of the hotspot activities over the ASEAN region in June 2015 are shown in Figs. 2A to 2E.

1.1    Inter-Monsoon season, which is characterised by light wind and wet weather conditions, prevailed over the ASEAN region in May 2015. The northward migration of the monsoon trough during the period brought persistent shower activities over the northern ASEAN region.

1.2    Super Typhoon Noul, which developed in early May 2015 from a tropical depression in the western Pacific Ocean made landfall over Cagayan in northeastern Luzon Island in the Philippines on 10 May 2015. “Noul” continued to track northeast towards Okinawa, Japan before dissipating in the North Pacific Ocean.F

1.3    In southern ASEAN, wet weather conditions generally prevailed until mid-May. Due to the northward migration of the monsoon trough, the shower activities had gradually eased off by late May.

1.4    In May 2015, most parts of northern ASEAN region received less than 50% of normal rainfall. Most of the southern ASEAN region, except Java, received 50 – 75 % of normal rainfall. The regional rainfall distribution for May 2015 is shown in Fig. 1A.

2.1    Persistent shower activities prevailed in May 2015 over the ASEAN region. The hotspot activities were generally subdued, and there were no occurrences of significant transboundary haze during the review period

2.2    During periods of drier weather conditions in May 2015, isolated hotspots with localized smoke haze were observed on a few days. Satellite images depicting some of the hotspot activities over the ASEAN region in May 2015 are shown in Figs. 2A to 2D.

1.1    Inter-Monsoon conditions prevailed over the ASEAN region in April 2015. The gradual northward migration of the monsoon trough brought an increase of shower activities over most parts of ASEAN region, especially towards late-April.

1.2    In April 2015, less than 50% of normal rainfall was received in most parts of northern ASEAN region except northern Thailand and Luzon Island in the Philippines. In the southern ASEAN region, near-normal rainfall was received across most parts. Less than 75% of normal rainfall was received mainly over southern Peninsular Malaysia, northern Sumatra and northern Borneo. The regional rainfall distribution for April 2015 is shown in Fig. 1A.

2.1    In April 2015, there was a gradual reduction in hotspot activities over the northern ASEAN region due to increased shower activities in the region. Localised smoke haze and hotspot activities were observed in early-April especially in the northern parts of Lao PDR and Vietnam, as well as in areas around the border between Thailand and Myanmar. Towards the later part of April 2015, persistent shower activities further subdued hotspot activities in the northern ASEAN region

2.2    In the southern ASEAN region, hotspot activities were generally subdued by widespread shower activities that affected the region. Satellite images depicting some of the hotspot activities over the ASEAN region in April 2015 are shown in Figs. 2A to 2E.

1.1    In the last week of March 2015, weak to moderate Northeast Monsoon conditions gave way to Inter-Monsoon conditions, and prevailing winds gradually weakened to become light and variable. The traditional dry season in the northern ASEAN region continued to prevail in the first half of the month, with drier weather conditions experienced mostly over northern Thailand and Myanmar. By late march 2015, a return of showers activities brought some respite to the dry weather conditions experienced in the past few months in the near-equatorial and northern ASEAN regions.

1.2    In March 2015, less than 50% of normal rainfall was received in most parts of the northern ASEAN region while in parts of central Thailand, Lao PDR and Vietnam received more than 125% of normal rainfall. In the southern ASEAN region, below normal rainfall was recorded over Peninsular Malaysia, Sabah, Sarawak and Kalimantan. The regional rainfall distribution for March 2015 is shown in Fig. 1A.

2.1    In March 2015, hotspot activities over northern Thailand, Myanmar and Cambodia remained elevated under the prevailing dry weather conditions. Parts of Myanmar and the northern provinces of Thailand were shrouded in occasional moderate haze for an extended period of time. In particular, elevated levels of PM10 were reported in several provinces in northern Thailand, namely- Chiang Mai, Maehongsorn and Lampung. The haze situation in northern Thailand and Myanmar improved with an increase in shower activities in late March 2015.

2.2    In the southern ASEAN region, hotspot activities were generally subdued in most parts of March 2015. During brief periods of drier weather, isolated hotspots with localised smoke haze were observed in central Sumatra. Satellite images depicting some of the hotspot activities over the ASEAN region in March 2015 are shown in Figs. 2A to 2E.

2.3    The hotspot charts for March 2015 for

1. Cambodia, Myanmar, Thailand, Lao PDR and Vietnam;
2. Sumatra, Borneo and Peninsular Malaysia; and
3. Java, Sulawesi and the Philippines

are shown in Figs. 2F to 2H respectively