Category Archives: Fortnightly Weather Review

1.1 Inter-monsoon conditions prevailed in May 2018, and most parts of the ASEAN region experienced an increase in shower activities. The increased shower activities brought an end to the dry season in the northern ASEAN region.

1.2 In May 2018, most parts of the Mekong sub-region received below-normal to near-normal rainfall except for the northern parts of Myanmar, eastern Cambodia and southern Vietnam where above-normal rainfall was recorded.

1.3 In the southern ASEAN region, below-normal rainfall was experienced over the northern parts of Sumatra, eastern Peninsula Malaysia, Java, and parts of Kalimantan. Elsewhere, near-normal to slightly above-normal rainfall were received.

1.4 The rainfall distribution for May 2018 and the percentage of normal rainfall for May 2018 are shown in Figure 1 and 2.

1.5 In the last week of May 2018, a low-pressure system developed over the Bay of Bengal and tracked north to northeast-wards toward Myanmar before making landfall around end May. The rain band associated with the low pressure system brought strong winds and heavy rain over many parts of Myanmar, including Yangon and Mandalay.

1.6 Over the South China Sea and the southern part of the Mekong sub-region, the northeasterly/easterly wind component was anomalously strong. Prevailing winds typically blow from the southwest or west in May, and the wind anomaly in May 2018 could be due to a persistent ridge over the southern coast of China from which there was an outflow of northeasterly and easterly winds. Figure 3 shows the average and anomalous winds at 5000 feet.

1.7 The El Niño-Southern Oscillation (ENSO) remained neutral (neither El Niño or La Niña) in May 2018. The atmospheric and oceanic indicators of ENSO such as sea surface temperature and trade winds were also indicative of neutral conditions.

1.8 In May 2018, the Madden Julian Oscillation (MJO) progressed from Phase 1 to Phase 4 from the second week of the month. The MJO in Phase 3 and 4 typically brings slightly enhanced rainfall over the southern ASEAN region during this time of the year. In the last week of May 2018, an increase in rainfall was observed over parts of the southern ASEAN region.

2. Review of Land/Forest Fires and Smoke Haze Situation

3. Status of El Niño/La Niña and Indian Ocean Dipole

1.1 The Northeast Monsoon conditions gave way to the inter-monsoon conditions in April 2018. The inter-monsoon period is characterised by afternoon showers with winds that are generally light and variable in direction. In April 2018, a gradual increase in shower activities was observed over parts of the Mekong sub-region, while in the southern ASEAN region, conditions were generally wet.

1.2 In the northern ASEAN region, most parts of the Mekong sub-region received near-normal to above-normal rainfall, except for parts of Myanmar, eastern Thailand and southern Vietnam.

1.3 In the southern ASEAN region, Peninsula Malaysia and Sumatra received below-normal rainfall. Near normal to below-normal rainfall were received over southern Kalimantan and Java.

1.4 The rainfall distribution for April 2018 and the percentage of normal rainfall for April 2018 are shown in Figure 1 and 2.

1.5 In April 2018, prevailing winds in the region were predominantly blowing from the northeast or southeast, with comparatively weaker winds within the equatorial belt between 5ºN and 5ºS. Stronger northeasterly winds were observed over the South China Sea, while anomalously strong westerly winds continued to be observed to the east of Sulawesi since March 2018. Figure 3 shows the average and anomalous winds at 5000 feet.

1.6 During the month, the El Niño-Southern Oscillation (ENSO) remained at neutral (neither El Niño or La Niña) conditions. The sea surface temperature over the central tropical Pacific Ocean, as well as the cloudiness and trade wind conditions were also indicative of neutral conditions.

1.7 The Madden Julian Oscillation (MJO) progressed from Phase 7 to Phase 2 during the first half of the month before propagating to Phase 3 during the third week of April 2018. The MJO in Phase 2 and 3 typically brings suppressed rainfall over the area around the Philippines, and slightly enhanced rainfall over the southern ASEAN region during this time of the year. However, the MJO event in April 2018 did not have a significant influence on the weather patterns in the ASEAN region. For the rest of the month, the MJO signal remained weak.

2. Review of Land/Forest Fires and Smoke Haze Situation

3. Status of El Niño/La Niña and Indian Ocean Dipole

1.1    The Northeast Monsoon conditions continued to prevail in Southeast Asia in March 2018. Dry air from the northern Asian landmass brought dry conditions to many parts of Southeast Asia, extending as far south as over Peninsular Malaysia. The northern ASEAN region remained in the midst of the traditional dry season, while wetter conditions were experienced in the south with the monsoon trough and its associated rain band lying close to the Equator.

1.2    In the northern ASEAN region, drier conditions were observed over Myanmar, northern Thailand and parts of Cambodia and Thailand while near to above-normal rainfall was felt over other parts of the region.

1.3    In the southern ASEAN region, parts of Peninsula Malaysia and northern Sumatra experienced below-normal rainfall.

1.4    The rainfall distribution for March 2018 and the percentage of normal rainfall for March 2018 are shown in Figure 1 and 2.

1.5    In March 2018, winds north of the Equator were predominantly from the east or southeast, while at and south of the Equator, the winds were generally from the west or north. During the month, strong anomalous northerly winds were observed over the Philippines. Stronger westerly winds were also observed between latitudes 8ºN and 8ºS, and longitudes 125ºE and 140ºE. Figure 3 shows the average and anomalous winds at 5000 feet.

1.6    During the month, the cool anomalies of the equatorial Pacific Ocean’s sea surface temperature (SST) over the Niño 3.4 region indicated neutral conditions (neither El Niño or La Niña) values. Trade winds and cloudiness over the equatorial Pacific Ocean has returned to near-average levels, which is also consistent with a neutral state.

1.7    During the first half of March 2018, the Madden Julian Oscillation (MJO) progressed through Phase 3, before gradually weakening towards the end of week 2. The MJO in Phase 3 typically brings slightly enhanced rainfall over the equatorial Southeast Asia region during this period of the year. However, the MJO event did not bring significant rainfall anomaly to the region in March 2018. For the rest of the month, the MJO signal remained weak.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1    In February 2018, Northeast Monsoon conditions continued to prevail over Southeast Asia with the northern ASEAN region still in the midst of the traditional dry season, and the southern ASEAN region experiencing wet weather conditions or it traditional rainy season.

1.2    In the northern ASEAN region, dry weather conditions were felt mostly over Myanmar, Cambodia and parts of Thailand and Vietnam. With the presence of the monsoon trough and its associated rain band lying close to the Equator, most parts of the southern ASEAN region experienced wet weather conditions in February 2018.

1.3    The rainfall distribution for February 2018 and the percent of normal rainfall for February 2018 are shown in Figure 1 and 2.

1.4    In the first half of February 2018, a mass of dry continental air from the northern Asian landmass brought dry and warm conditions to many parts of Southeast Asia, extending from northern Myanmar to as far south as over southern Peninsular Malaysia, Singapore and central Sumatra. During the first two weeks of February 2018, most of the shower activities fell over parts of Southeast Asia, south of the Equator, and near-normal rainfall was recorded there.

1.5    The tropical cyclone activity in February was low. There was only one tropical cyclone, Tropical Storm “Sanba” which developed on 11 February 2018 over the Pacific Ocean, east of Mindanao, the Philippines. Tropical Storm “Sanba” tracked to the west and made landfall over Mindanao, the Philippines two days later. “Sanba” brought heavy rainfall, strong wind gusts of around 75km/h and landslides in parts of the central and southern Philippines as the storm moved west northwest across the Philippines towards the South China Sea before it dissipated off the coast of Vietnam. Figure 3 shows the storm track of Tropical Storm Sanba.

1.6    In February 2018, the prevailing winds over Southeast Asia, north of the Equator blew predominantly from the northeast or east, while around and to the south of the Equator, the winds were generally from the west or northwest. During the month, there were strong anomalous westerly winds observed between latitudes 10^o N and 10^o S, and from 120^o E to 170^oE. Figure 4 shows the average and anomalous winds at 5000 feet.

1.7    During the month, the sea surface temperature (SST) over the Niño 3.4 region in the equatorial Pacific Ocean remained at La Niña values, but the cool anomalies showed a gradually declining trend. Cloudiness over the equatorial Pacific Ocean was slightly below average during the month, indicative of a weakening of the La Niña conditions. Although the SST and cloudiness were suggestive of La Niña conditions, the trade winds over the equatorial Pacific Ocean, were observed to be near-normal, partly due to the occurrence of the westerly wind burst associated with the active MJO phase 7 and 8.

1.8    The Madden Julian Oscillation (MJO) was active throughout the month, propagating from a start phase of Phase 7 and ending in Phase 2 towards the end of the month. In addition to the occurrence of the mass of dry and warm air over most parts of Southeast Asia in the first half of February 2018, rainfall in these areas were also suppressed due to the MJO which was in phase 7 and 8. The shift in the MJO to phase 1 and 2 towards the end of the month contributed to an increase in intense organised convection over the eastern Indian Ocean, and brought an increase in shower activities over the southern ASEAN region.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1    The prevailing Northeast monsoon conditions over Southeast Asia strengthened in January 2018. Wet weather conditions were mostly over the Philippines and the southern ASEAN region, while drier weather conditions were experienced over the northern ASEAN region, particularly over Lao PDR and Cambodia. The rainfall distribution for January 2018 is shown in Figure 1.

1.2    In January 2018, there were two occurrences of monsoon surges which brought strong winds and moderate to heavy rainfall over the equatorial region, in particular over Borneo, Peninsular Malaysia and Singapore.

1.3    Southern ASEAN region received near to above-normal rainfall, except for the southern half of Sumatra, southwest parts of Borneo, parts of Sulawesi and Java, where below-normal rainfall were received. In the northern ASEAN region, below-normal rainfall was received over parts of Cambodia, Thailand, Laos PDR and Vietnam. Figure 2 shows the percent of normal rainfall for January 2018.

1.4    On 2 January 2018, Typhoon “Bolaven” (Figure 3) developed over the southern part of the Philippines and tracked westwards bringing heavy rainfall over the southern Philippines and the South China Sea. Typhoon “Bolaven” moved into the South China Sea on 3 January 2018 and dissipated over the sea before it reached the eastern coast of Vietnam.

1.5    The prevailing winds in January 2018 were mainly from the northeast or east over the northern ASEAN region and the South China Sea while, westerly and northwesterly winds were observed over the southern ASEAN region. In addition, strong anomalous westerly winds were recorded between latitudes 5^o N and 10^o S, extending from the Indian Ocean to 125^o E. Figure 4 Figure 5 shows the average and anomalous winds at 5000 feet. The convergence between the northeast winds over the northern ASEAN region and the westerly winds over the southern ASEAN region contributed to the observed above-normal rainfall around the equatorial region.

1.6    The sea surface temperatures (SSTs) over the Niño 3.4 region in the equatorial Pacific Ocean remained at La Niña values, with stronger than average trade winds and below-average cloudiness over the equatorial Pacific Ocean, indicative of La Niña conditions. Typically, La Niña brings wetter-than-normal rainfall conditions to most parts of Southeast Asia, and has a less pronounced impact on the weather over the near-equatorial region during the Northeast Monsoon season.

1.7    The Madden Julian Oscillation (MJO) was active throughout most of January 2018, propagating from a start phase of Phase 2 and ending in Phase 6 towards the end of the month. The monsoon surges that affected the region in the first half of the month coincided with MJO phases 2 and 3. This brought heavy rainfall over the southern parts of the South China Sea. As the MJO shifted to phases 5 and 6, the rainfall conditions over most parts of ASEAN were suppressed.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1    In December 2017, Southeast Asia experienced northeast monsoon conditions with drier weather conditions over the northern ASEAN region, and rainy or wet weather conditions in the southern ASEAN region. Most of the rain during the month fell within the region bounded between 10oS and 10oN of the Equator. The most intense rain that fell during the month was over the central South China Sea and to the east of the Philippines. These areas coincided with the path of the tropical cyclones crossing the central South China Sea, north of Borneo after making landfall in the Philippines. The rainfall distribution for December 2017 is shown in Figure 1.

1.2    In the second half of December 2017, intensification of the high pressure system in northern Asia brought a monsoon surge or a sudden surge of cold winds over the South China Sea. As these strong northeasterly winds blew equatorward over the South China Sea, it gathered moisture and led to the development of persistent rain clouds over large parts of the equatorial region. The surges brought strong winds and spells of moderate to heavy rain to Borneo, Peninsular Malaysia and Singapore. In particular, the eastern coastal states of Peninsular Malaysia and northern coast of Borneo were affected by heavy rainfall and intense floods arising from the monsoon surges.

1.3    Above-normal rainfall was recorded in most parts of the northern ASEAN region except for the eastern parts of Cambodia and the southern parts of Laos and Vietnam where below-normal rainfall was received. Most parts of the southern ASEAN region received normal to above-normal rainfall. Figure 2 shows the percent of normal rainfall for December 2017.

 

 

1.4    In December 2017, 3 tropical cyclones brought heavy rainfall and strong winds to the region. On 1 December, Tropical cyclone “Dahlia” (Figure 3) moved over the Indian Ocean, south of Java, bringing heavy rains to Java’s southern coast. On 14 December, a tropical depression (Figure 4) over the western Pacific Ocean, east of Cebu, the Philippines, intensified into Typhoon “Kai-Tak” and tracked over the South China Sea towards Peninsular Malaysia after making landfall in central Philippines. Heavy rain from the bands of “Kai-Tak” fell over the eastern coastal states of Peninsular Malaysia. As “Kai-Tak” dissipated over the South China Sea, another tropical depression over the western Pacific Ocean developed and tracked westwards and intensified into Typhoon “Tembin” over the South China Sea (Figure 4) before dissipating over water as it approached the southern Vietnam.

1.5    In December 2017, prevailing winds blew predominantly from the northeast or east in the northern ASEAN region and from the west or northwest in the southern ASEAN region. Strong anomalous westerly winds were recorded between 5o S and 10o N, extending from the Indian Ocean to the western Pacific Ocean due to the passage of typhoons “Kai-Tak” and “Tembin” in the South China Sea. Figure 5 shows the average and anomalous winds at 5000 feet.

1.6    During the month, sea surface temperatures (SSTs) over the Niño 3.4 region in the equatorial Pacific Ocean remained at La Niña values. The stronger than average trade winds and below-average cloudiness indicate La Niña conditions.

1.7    The Madden Julian Oscillation (MJO) was active throughout most of December 2017, propagating from a start phase of Phase 5, ending in Phase 2 towards the end of the month. The MJO however did not play a significant role in modulating the rainfall over the Southeast Asia regions. The rainfall was more likely modulated by the typhoons and monsoon surges in the region.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1    In November 2017, Southeast Asia experienced inter-monsoon conditions in the first half of the month where the low level winds were generally light and variable in direction. A gradual strengthening of winds to blow predominantly from the northeast in the second half of November 2017 signalled the start of the Northeast Monsoon season. In the latter half of the month, the monsoon rain band was observed to shift southwards to lie between latitudes 10 ^o S and 10 ^o N. Most of the rainfall in November 2017 was recorded over the southern ASEAN region. The rainfall distribution for November 2017 is shown in Figure 1.

1.2    In the last week of November 2017, an intensification of a high pressure system in northern Asia led to a strengthening of northeast monsoon winds or a monsoon surge over the South China Sea. The surge brought prolonged moderate to heavy rainfall over southern Thailand and the north-eastern parts of Peninsular Malaysia. Widespread flooding was reported in Songkhla, Thailand, as well as in parts of Kelantan and Terengganu, Peninsular Malaysia.

1.3    In November 2017, rainfall was above normal in central Vietnam, southern Thailand and in the northern parts of the Philippines, and below normal in northern Thailand, Lao PDR and northern Vietnam. For the southern ASEAN region, normal to above-normal rainfall was recorded over most parts of the region. Figure 2 shows the percent of normal rainfall for November 2017.

 

1.4    On 1 November 2017, a tropical depression developed to the west of Cebu, the Philippines. The system tracked westward over the South China Sea where it intensified into Typhoon “Damrey” on 3 November 2017. Typhoon “Damrey” brought rough seas and strong winds along its path and made landfall in central Vietnam on 4 November 2017. The typhoon brought heavy rains and strong winds, and caused widespread flooding over many provinces in central Vietnam before dissipating over land on 5 November 2017.

1.5    In November 2017, the prevailing winds over the northern ASEAN region blew mainly from the northeast or east while winds in the southern ASEAN region were generally light and blew from the west or northwest. Broad easterly wind anomalies were observed over the western Pacific Ocean while westerly or north-westerly wind anomalies extended from the Indian Ocean to the Java Sea. The presence of the monsoon trough, coupled with the convergence of winds and strong solar heating enhanced the convective activity over southern Southeast Asia. Figure 4 shows the average and anomalous winds at 5000 feet.

1.6    During the month, the equatorial Pacific Ocean’s sea-surface temperature (SST) over the Nino 3.4 region remained at borderline La Niña values, with the 3-month (Aug-Sep-Oct) Nino 3.4 index at -0.46. Atmospheric conditions, such as trade winds and cloudiness, over the equatorial Pacific were suggestive of weak La Niña conditions.

1.7    The Madden Julian Oscillation (MJO) was weak and non-discernible throughout most parts of November 2017. However, signs of Phase-4 MJO were observed in late-November which coincided with a monsoon surge. The development of Phase-4 MJO could have enhanced the intensity of the monsoon surge that affected the region.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1 Southwest Monsoon conditions continued to prevail in the first half of October 2017 and gradually transitioned to the inter-monsoon conditions in the second half of the month. The prevailing southeasterly to southwesterly winds over the ASEAN region gradually weakened to become more light and variable in direction.

 

1.2    During the month, most of the shower activities fell over the equatorial region between 5 S and 15 N. Figure 1 shows the rainfall distribution over the ASEAN region during the month of October 2017. Rainfall was below-normal over the eastern and southern parts of Thailand, and over the northern parts of Peninsula Malaysia and parts of East Malaysia. For most parts of the ASEAN region, rainfall was normal to above-normal. Figure 2 shows the percent of normal rainfall for October 2017.

1.3    The occurrence of several tropical cyclones in the first half of October 2017 brought heavy rainfall to some parts of the northern ASEAN region. Among these tropical cyclones, Tropical Depression ‘23W’ and Typhoon ‘Khanun’ brought heavy rainfall and strong winds to the Philippines and Vietnam. Tropical Depression ‘23W’ developed over the South China Sea on the 9 October 2017, which tracked west-northwest and made landfall over the northern coast of Vietnam on 10 October 2017. On 12 October 2017, Tropical Storm ‘Khanun’ developed over the east of Luzon in the Philippines. It tracked westwards and intensified into a typhoon over the South China Sea on the 15 October 2017, and continued to track westwards before making landfall over the southern coast of China. Typhoon ‘Khanun’ weakened and continued to track southwest bringing torrential rain and strong winds over northern Vietnam.

2.1     Hotspot activities in the northern ASEAN region were generally subdued in the first three weeks of October 2017 due to wet weather conditions. However, during the last week of the month, dry weather conditions prevailed over the region, with isolated hotspots detected mainly over Myanmar. In the southern ASEAN region, isolated hotspots were detected over West Kalimantan, northern Sumatra and southern Sumatra.
2.2     In the later part of October 2017, Sumatra and Kalimantan experienced periods of dry weather conditions. This contributed to a slight increase in the hotspot activities detected mainly over West Kalimantan, northern Sumatra and southern Sumatra. There were no smoke haze and plumes observed near the vicinity of the hotspots. The return of shower activities during the last few days of the month helped to alleviate the hotspot situation in the southern ASEAN region. Satellite images depicting some of the hotspot activities over parts of the ASEAN region in October 2017 are shown in Figures 6 to 10.

 

2.3    The hotspot distribution charts and daily hotspot charts for October 2017 are shown in Figure 11, Figure 12 and Figure 13 respectively.

 

3.1    Most models from major international climate centres have projected that the sea surface temperatures would continue to cool towards the end of 2017. During this period, the prevailing La Niña-like conditions are expected to be short-lived and persist until early 2018.

3.2    The region is currently experiencing Northeast Monsoon conditions. The impact of La Niña on the weather over the near-equatorial region is usually less pronounced during the Northeast Monsoon as compared to the Southwest Monsoon (Jun – Sep).

3.3    In October 2017, the Indian Ocean Dipole (IOD) index was neutral (Figure 14). In the coming months, international climate models forecast the IOD to remain neutral and it is not likely to have a significant influence on the weather over the region for the next few months. The formation of IOD typically starts around May or June, and peaks between August and October before decaying rapidly between December and April.

1.1    In September 2017, Southwest Monsoon conditions prevailed over the ASEAN region, and the monsoon rain band migrated further south with most of the shower activities occurring over the equatorial region between 5^oS and 15^oN. The rainfall distribution for September 2017 is shown in Figure 1.

1.2    During the month, rainfall was below-normal over northern and central Thailand, while normal to above-normal rainfall prevailed for other parts of the northern ASEAN region. In contrast, for the southern ASEAN region, rainfall was mostly above-normal, particularly over Malaysia, Sumatra, Sulawesi and Papua. Figure 2 shows the percentage normal of rainfall for September 2017.

1.3    In September 2017, there were several tropical cyclones that brought heavy rainfall to Asia Pacific region. Among these tropical cyclones, only typhoon ‘Doksuri’ brought heavy rainfall and strong winds to the Philippines and Vietnam. “Doksuri” developed on 10 September 2017, and made landfall over Luzon, the Philippines before moving westwards over northern Philippines and into the South China Sea. ’Doksuri’ intensified into a typhoon as it continued to track west-northwestward over the South China Sea towards Vietnam. On 15 September 2017, Typhoon Doksuri made landfall near the north central regions of Vietnam. In addition to the torrential rain and strong winds, the coastal provinces of Vietnam experienced storm surges which accompanied the typhoon, Typhoon Doksuri weakened and dissipated shortly after making landfall.

 

1.4    The prevailing winds during September 2017 were predominantly from the southeast or southwest, particularly over the southern ASEAN region. In the northern ASEAN region, winds were light and blew from the south or southwest. Broad easterly wind anomalies were observed over the western Pacific Ocean and parts of the South China Sea. Figure 4 shows the average and anomalous winds at 5000 feet.

1.5    In September 2017, the equatorial Pacific Ocean’s sea-surface temperature (SST) over the Nino 3.4 region remained at neutral (neither El Niño nor La Niña) values. However, in recent weeks, there has been a gradual cooling of the sea surface temperatures, and the Nino 3.4 index dipped to negative values. However, atmospheric conditions, such as trade winds and cloudiness, over the equatorial Pacific have largely remained neutral.

1.6    The Madden Julian Oscillation (MJO) was weak and non-discernible in September 2017. Although there was a faint and brief MJO signal in Phase 3 in mid-September 2017, overall, the MJO did not have a significant influence on the weather conditions over the southern ASEAN region.during the month.

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Status of El Niño/La Niña and Indian Ocean Dipole

1.1    Southwest Monsoon conditions continued to prevail in the region in August 2017. The monsoon rain band was located in the Northern Hemisphere, between latitude 5^oN and 20^oN, and brought extensive rainfall over the region. Heavy rain fell over the coastal regions of Myanmar and the northern parts of the Philippines. For the southern ASEAN region, dry weather conditions were experienced over parts of southern Sumatra and Java. The rainfall distribution for August 2017 is shown in Figure 1.

 

1.2    In August 2017, rainfall was near-normal to above-normal over the northern ASEAN region except in Cambodia where rainfall was below-normal. In the southern ASEAN region, near-normal to above-normal rainfall prevailed except in southern Sumatra and parts of Java where rainfall was below-normal. Figure 2 shows the percent normal of rainfall for August 2017.

1.3    Two tropical storms – Hato and Pakhar were brewing in August 2017 over the western Pacific Ocean. Tropical Storm Hato developed to the northeast of the Philippines on the 20 August 2017. It tracked westwards and made landfall over the coast of southern China on the 23 August 2017. Tropical Storm Pakhar developed over the sea areas to the east of Luzon, the Philippines, on the 25 August 2017, and tracked north-westwards, crossing over northern Philippines before making landfall over the coast of southern China on the 27 August 2017. Both tropical storms brought heavy rains to Hong Kong and widespread shower activities over the northern ASEAN region.

 

1.4    The prevailing winds in August 2017 were predominantly from the southwest in the northern ASEAN region, and from the southeast in the southern ASEAN region. Figure 3 shows the average and anomalous winds at 5000 feet. In the month of August 2017, anomalous northeasterly to easterly winds dominated over the South China Sea and the region east of the Philippines. Furthermore, an anomalous cyclonic circulation was observed over the South China Sea, east of Hainan Island, associated with the tropical storms Hato and Pakhar.

 

1.5    In August 2017, the equatorial Pacific Ocean’s sea-surface temperature (SST) over the Nino3.4 region was close to the El Niño Nino 3.4 index threshold. Most of the atmospheric indicators such as wind and cloudiness were fluctuating about the neutral values.

1.6    During the month, the Madden Julian Oscillation (MJO)1 was generally weak and non-discernible except for a brief period in Phase 2 towards the end of August 2017. Overall, the contribution by the MJO on the weather over the Maritime continent in August 2017 was not significant.

 

2.   Review of Land/Forest Fires and Smoke Haze Situation

3.   Outlook of El Niño/La Niña and Indian Ocean Dipole