Category Archives: News

WEATHER OUTLOOK (16 – 31 December 2019)

Singapore, 16 December 2019 – Singapore and the surrounding region are currently in the wet phase of the Northeast Monsoon season. This phase is expected to prevail into January 2020 before transitioning to the dry phase of the season (February – mid-March). For the second fortnight of December 2019, the low-level winds are forecast to blow from the northwest or northeast.

2          For the rest of December 2019, strong daytime heating of land areas coupled with localised convergence of winds are expected to influence the weather in Singapore on eight to ten days in the fortnight. These conditions are conducive for localised thunderstorm cloud development, and are forecast to bring moderate to heavy thundery showers in the afternoon. On some of these days, the showers could extend into the evening. Showers are likely around the Christmas period. Overall, the rainfall for December 2019 is expected to be well above average.

3          In the last fortnight of 2019, the daily temperatures are forecast to range between 24°C and 33°C on most days, and could dip to a low of around 23°C on a few days.

4         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 15 December 2019)

5          Northeast Monsoon conditions prevailed over Singapore and the surrounding region in the first fortnight of December 2019.  During the period, it was windy with low-level winds blowing from the northeast or east, arising from the monsoon surge that prevailed on most days over the equatorial Southeast Asia region including Singapore.

6          On the first few days of December 2019, strong solar heating of land areas coupled with convergence of winds in the surrounding region brought moderate to heavy thundery showers in the afternoon. The intense thundery showers on 2 December 2019 recorded a daily total rainfall of 102.8mm at Bukit Panjang. This was the highest daily total rainfall recorded for the first fortnight of December 2019. A surge of northeast monsoon winds prevailed throughout the fortnight since 5 December 2019, and brought cloudy and windy conditions to Singapore. While there were some passing showers over the island in the first week, periods of moderate to occasionally heavy rain/showers fell on all but one day in the second week of December 2019. Over the 13 December 2019 weekend, the rain was widespread and fell continuously over the island before dissipating in the evening of 15 December 2019. The highest daily total rainfall recorded over this weekend was 80.9mm on 15 December 2019 at Loyang. The highest daily total rainfall recorded throughout this monsoon surge event was 100.4 mm on 9 December 2019 at Pulau Ubin.

7          Compared to the last fortnight of November 2019, the rainy weather in the first fortnight of December 2019 brought cooler temperatures across Singapore. The daily maximum temperature in the first week of the fortnight ranged between 27.3°C and 34.9°C but dipped to between 25.2°C and 32.3°C in the second week of the fortnight due to the rainy weather arising from the monsoon surge. The lowest daily maximum temperature of 25.2°C was recorded on 15 December 2019 at Changi. The lowest daily minimum temperature recorded in the fortnight was 21.4°C on 2 December 2019 at Admiralty, arising from the intense thunderstorm that fell over the island that afternoon.

8          In the first half of December 2019, Singapore recorded above-average rainfall across the island. Pasir Ris recorded the highest rainfall anomaly of 151% while Ulu Pandan recorded the lowest rainfall anomaly of 10% above average.

CLIMATE STATION STATISTICS

Long-term Statistics for December
(Climatological reference period: 1981 – 2010)

Historical Extremes for December
(Rainfall since 1869 and temperature since 1929)

WEATHER OUTLOOK (30 November – 15 December 2019)

1        Singapore has been experiencing Northeast Monsoon conditions since early November 2019, and these conditions are expected to last until March 2020. During this period, the prevailing winds are forecast to blow from the north or northeast.

2          The Northeast Monsoon season has two phases, a wet phase typically between December and January and a dry phase, usually between February and March. During the first phase of the season, the monsoon rain band lies over the equatorial South China Sea, and usually brings increased cloudiness and rain showers over Singapore and the surrounding region. In addition, on occasions when there is an intensification of a high-pressure system over the northern Asian continent, this could bring a surge or strengthening of northeast winds over the South China Sea, blowing toward the equatorial Southeast Asia region. Singapore and the surrounding region can expect a few such monsoon surges[1] during the wet phase of the season, and the surge can bring several days of widespread continuous rain/showers over southern Johor and Singapore.

3          In the first week of December 2019, the southern South China Sea region including Singapore can expect a monsoon surge lasting from two to four days. The surge is likely to bring cloudy and occasionally windy conditions with periods of widespread moderate to heavy showers over Singapore. The strong northeasterly winds over the South China Sea are forecast to weaken in the second week of December 2019. For the rest of the fortnight, Singapore can expect short-duration moderate to heavy thundery showers in the afternoon on five to seven days. This is due to strong solar heating of land areas coupled with localised convergence of winds. Overall, most parts of Singapore can expect above-normal rainfall in the first fortnight of December 2019.

4          The monsoon surge event in the first week December 2019 is also expected to bring cooler daily temperatures of between 22°C and 30°C.  For the rest of the fortnight, the daily temperatures are forecast to range between 24°C and 33°C, and could dip to a low of 23°C on a few nights. The daily maximum temperature could still reach a high of around 34°C on a few days.

5         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 29 November 2019)

5          In November 2019, the inter-monsoon conditions transitioned to the Northeast Monsoon conditions as the low-level winds which were light and variable in direction, strengthened to blow from the northwest or northeast.

6          During the month, strong solar heating of land areas coupled with localised convergence of winds led to the development of short-duration thundery showers over Singapore. The showers fell mostly in the afternoon, and on some days, extended into the evening. The thundery showers at Loyang (as at 5:31 pm) on 29 November 2019 recorded a daily total rainfall of 102.5 mm. This is the highest daily total rainfall recorded for November 2019. On that day, thundery showers fell over many parts of the island in the afternoon due to a convergence of winds over the surrounding region.

7          Although it rained across the island on most days of the month, more than half the month still recorded daily maximum temperatures of above 34°C. On 7 November 2019, the highest daily maximum temperature recorded at all stations across the island was 35.0°C at Paya Lebar on 10 Nov 2019.

8          At the climate station in Changi, the highest daily maximum temperature recorded in November 2019 (as of 28 November 2019) was 34.4°C on 17 November 2019. Based on long-term climate station records, this is 0.2°C higher than the highest ever-recorded daily maximum temperature in November on 26 November 2000. November 2019 is also likely to be on track to be the warmest  November since temperature records began in 1929, with mean temperature of 28.1°C (as of 28 November 2019). This is 0.1°C above the highest record of 28.0°C in November 1998 and 2015.

9          In November 2019, many parts of Singapore recorded below-average rainfall. Sentosa recorded the highest rainfall anomaly of 79% below average while Choa Chu Kang recorded the highest rainfall anomaly of 18% above average.

[1] A monsoon surge refers to the strengthening of northeasterly winds blowing from a strong high-pressure system over the northern Asian continent toward the South China Sea, bringing periods of prolonged widespread rain and windy conditions to the surrounding region including Singapore and Peninsular Malaysia. (Further information is available at  https://www.weather.gov.sg/learn_weather_systems/)

CLIMATE STATION STATISTICS

Long-term Statistics for December
(Climatological reference period: 1981 – 2010)

Historical Extremes for December
(Rainfall since 1869 and temperature since 1929)

Singapore, 15 November 2019 – In the second half of November 2019, the prevailing inter-monsoon conditions are expected to transition to the Northeast Monsoon. During this period, the prevailing low-level winds that are light and variable in direction are forecast to gradually strengthen and blow from the northeast or northwest. The Northeast Monsoon season, which is also the rainy season over southern Southeast Asia, is expected to extend into March 2020.

2          During the Northeast Monsoon season, the low-level winds originating from East Asia gather moisture as they pass over the South China Sea and converge over the equatorial Southeast Asia region. This enhances the development of the monsoon rain band lying over the region, and brings more showers to Singapore and the surrounding region. As a result, coupled with strong solar heating of land areas during the day, Singapore can expect short-duration thundery showers in the afternoon on seven to nine days in the second half of November 2019.

3          Around the end of the month, a further strengthening of the northeasterly winds over the equatorial South China Sea is expected. This is likely to bring cloudy conditions and moderate to heavy thundery showers over Singapore between the late morning and evening on one or two days. Overall, the rainfall for November 2019 is likely to be near-normal for most parts of Singapore.

4          With more rain days forecast in the last two weeks of November 2019, it is expected to be slightly cooler compared to the warm days experienced over the past weeks. The daily temperature on most days is forecast to range between 24°C and 33°C. There could still be one or two warm days where the daily maximum temperature could reach a high of around 34°C. On a few nights, the daily minimum temperature could reach a low of around 23°C.

5          For the rest of November 2019, the gradual strengthening of the northeasterly winds over the equatorial Southeast Asia region is expected to alleviate any occasional slight haziness due to the accumulation of particulate matter in the atmosphere under light wind conditions.

6         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 15 November 2019)

7          In the first fortnight of November 2019, Singapore and the surrounding region experienced inter-monsoon conditions with low-level winds that were generally light and variable in direction.

8          In the fortnight, short-duration thundery showers fell over parts of the island between the late morning and afternoon on all but two days during the period. Compared to the last fortnight of October 2019, the showers in the first fortnight of November 2019 were less widespread and less intense. This was due to the slight northward shift of the monsoon rain band away from the Equator because of the development of low-pressure systems in the northern South China Sea and Pacific Ocean. On 5 November 2019, thundery showers fell over many parts of the island in the late morning and early afternoon due to convergence of winds feeding into rain bands extending from Typhoon Nakri in the South China Sea. The highest daily total rainfall recorded that day was 47.4mm over the southern part of the island at Kent Ridge.

9          Singapore recorded slightly warmer temperatures in the first fortnight of November 2019 compared to the last fortnight of October 2019. The daily maximum temperatures reached above 34°C for more than half of the fortnight, and the highest daily maximum temperature recorded was 34.9°C on 7 November 2019 at Marina Barrage and Ang Mo Kio.

10        On a few days toward the end of the fortnight, Singapore experienced slight haziness with the 24-hr PSI ranging between the high end of the Moderate and the low end of the Unhealthy range. The slight haziness was due to the accumulation of particulate matter in the atmosphere under light wind conditions. While some showers on 12 and 13 November 2019 helped to improve the air quality over the island, the light winds slowed the dispersion of the particles and the haziness lingered over the two days. The air quality improved to the Moderate range on 14 November 2019. This was due to the occurrence of showers over the island and surrounding vicinity and a strengthening and shift of winds to blow from the northeast over Singapore from the early hours of 14 November 2019.

11        In the first half of November 2019, most parts of Singapore recorded below-average rainfall. Sentosa recorded the highest rainfall anomaly of 96% below average while Ang Mo Kio recorded the highest rainfall anomaly of 14% above average.

CLIMATE STATION STATISTICS

Long-term Statistics for November
(Climatological reference period: 1981 – 2010)

Historical Extremes for November
(Rainfall since 1869 and temperature since 1929)

Singapore, 16 October 2019 – Singapore has been experiencing inter-monsoon conditions since early October 2019. These conditions are forecast to prevail for the rest of October and extend into November 2019.  The inter-monsoon period is characterised by thundery showers and low level winds that are light and variable in direction.

2          For the rest of October 2019, the low level winds are expected to be mostly light and variable in direction, and may strengthen and shift to blow from the southeast on a few days. This temporary change in winds can be partly attributed to the strengthening of a high pressure system over the southern Indian Ocean.

3          During the fortnight, the equatorial Southeast Asia region, including Singapore, can expect more showers in the first week of the fortnight. This is due to the presence of the monsoon rain band over the equatorial region coupled with convergence on winds in the surrounding vicinity. For Singapore, short-duration moderate to heavy thundery showers are forecast in the afternoon on eight to ten days. The thundery showers can extend into the evening on a few of these days, and can be accompanied by frequent lightning activity. Overall, the rainfall for Singapore in October 2019 is expected to be near-normal.

4         For the rest of the month, with the expected increase in rainfall over the region, the likelihood of transboundary haze affecting Singapore is low. However, Singapore could experience slightly hazy conditions on a few days, particularly in the early morning due to an accumulation of particulate matter in the atmosphere under light and variable wind conditions.

5          ​The warm conditions experienced in the first fortnight of October 2019 are forecast to continue for the rest of October 2019, with the daily maximum temperature reaching a high of 35°C on a few days. On most days, the daily temperature is forecast to range between 25°C and 34°C.

6         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 15 October 2019)

7        Southwest Monsoon conditions transitioned to inter-monsoon conditions in the first half of October 2018. The presence of the monsoon rain band located near the equatorial region brought more showers over Singapore and the surrounding region. This brought some relief to the dry weather conditions experienced in Singapore in recent months.

8          During the first fortnight of October 2019, short-duration thundery showers fell over the island mostly in the afternoon due to the light winds coupled with strong solar heating of land areas. On 7 October 2019, strong wind convergence over the equatorial Southeast Asia region brought widespread thundery showers over Singapore between late morning and evening. On that day, the daily total rainfall of 76mm recorded at Pasir Ris was the highest recorded daily total rainfall in the first half of October 2019.

9          Despite the increased showers, there were still some warm days with the daily maximum temperature exceeding 34°C. The highest daily maximum temperature of 35.7°C was recorded at Clementi on 13 October 2019.

10          Below-average rainfall was recorded across Singapore in the first half of October 2019. Sentosa recorded the highest anomaly of 92% below-average.

CLIMATE STATION STATISTICS

Long-term Statistics for October
(Climatological reference period: 1981 – 2010)

Historical Extremes for October
(Rainfall since 1869 and temperature since 1929)

New temperature and rainfall records for September 2019

Singapore, 1 October 2019 – In the first fortnight of October 2019, the prevailing Southwest Monsoon conditions with low level winds blowing from the southeast or south are forecast to gradually weaken to become light and variable in direction. This change in conditions signal the cessation of the Southwest Monsoon season and the start of the inter-monsoon period.

2          Inter-monsoon conditions are forecast to prevail through November 2019, and is characterised by light winds and thunderstorms that are intense at times. The light winds, high moisture and strong day time heating of land areas are conducive for thunderstorm development. Lightning activity tends to be higher during the inter-monsoon period compared to other times of the year.

3          The monsoon rain band that has been hovering over the equatorial Southeast Asia region since late September 2019 is forecast to maintain its position over the region in the coming fortnight. This is expected to bring short-duration thundery showers over Singapore, mostly in the afternoon on eight to ten days. On a few of these days, the thundery showers can be expected in the late morning and extend into the afternoon. The rainfall for the first fortnight of October 2019 is forecast to be slightly above-normal over most parts of Singapore.

4          In the coming fortnight, more showers are forecast for the southern Southeast Asia region. The increase in rainfall is expected to bring a further improvement to the haze situation in the region, and the likelihood of transboundary haze affecting Singapore is thus low. However, Singapore could experience slightly hazy conditions on a few days, particularly in the early morning, due to an accumulation of particulate matter in the atmosphere under light wind conditions.

5          The first half of October 2019 is also forecast to be warm with the daily maximum temperature exceeding 35°C on a few days. On most days, the daily temperature is forecast to range between 25°C and 34°C. The night-time temperatures in the southern and eastern coastal areas of the island are expected to be warmer with daily minimum temperatures of 27°C or more on some days.

6         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 30 September 2019)

7         In September 2019, Southwest Monsoon conditions prevailed over the region with the low level winds blowing from the southeast or south, and on occasions from the southwest.

8          Singapore experienced drier and warmer-than-normal conditions in the first three weeks of September 2019. These conditions were due to suppressed raincloud formation arising from dry air blown to the southern Southeast Asia region from high pressure systems over Australia, coupled with the persisting cooler sea surface temperatures over the tropical Indian Ocean. There were however a few days during this period when showers fell over Singapore. In particular, the thundery showers on 4 September 2019 due to convergence of winds over Singapore and the surrounding vicinity brought showers over many parts of the island. The highest daily total rainfall of 93.3mm recorded over Jurong West that day was the highest recorded for September 2019.

9          In contrast, the last week of September 2019 was wet. The rainy weather was due to the moisture-laden easterly winds that were blown to the southern Southeast Asia region from the tropical Pacific Ocean. On 27 September 2019, an intense thunderstorm over the Tuas area generated a rotating column of winds, known as a landspout, over Gul Way. The landspout, which is the first reported occurrence in Singapore, lasted for several minutes and ripped off parts of a building’s roof.

10          Between 9 and 23 September 2019, Singapore experienced hazy conditions due to smoke haze from land and vegetation fires in Sumatra blown in by the prevailing winds. The 24-hour PSI during this period was between the Moderate and Unhealthy range, and remained in the Unhealthy range on some days (14-15 Sep, 17-19 Sep and 21 – 23 Sep 2019). The highest 24-hour PSI reading of 154, in the mid-section of the Unhealthy range, was recorded in southern Singapore between 2am and 4am on 19 September 2019. Showers in the last week of September 2019 helped to ease the hazy conditions over Singapore.

11        September 2019 was warm with the highest daily maximum temperature across the island reaching at least 34°C on more than 15 days in the month. The highest daily maximum temperature of 35.0°C was recorded at Tai Seng on 21 September 2019.

12        Based on the climate station records, September 2019 is the warmest and the driest September in Singapore since temperature and rainfall records began in 1929 and 1869 respectively. The monthly mean temperature for September 2019 was 29.0^oC, 0.2^oC warmer than the previous record set in September 1997. September 2019 also saw a new record for the highest September mean daily maximum of 33.0^oC, far exceeding the previous record of 32.2^oC (in September 1997) by 0.8^oC. Another record was set for the highest September mean daily minimum temperature of 26.6^oC, 0.1^oC higher than the previous record in September 2015. The monthly total rainfall last month was 22.8 mm, breaking the previous September record low rainfall of 23.7 mm in September 1994.

13       Significantly below-average rainfall was recorded across Singapore in September 2019. The lowest anomaly of 85% or more below-average was recorded at a few stations in the eastern part of the island. The total rainfall recorded at rainfall stations across the island with long-term records for September 2019 was 44% below September’s climatological normal.  September 2019 is thus the third consecutive month, following July and August 2019, with more than 40% below-normal monthly rainfall giving rise to a rainfall deficit situation[1] (the total rainfall for July 2019 and August 2019 was 51% and 81% below normal respectively). The last occurrence of a rainfall deficit situation in Singapore was in 2014 from January to March, where the average rainfall total for each month across Singapore was 67%, 89% and 50% below the month’s normal.

[1] A rainfall deficit situation refers to a period of at least 3 consecutive months with monthly rainfall more than 40% below the climatological rainfall, averaged over the rainfall stations with long term records across the island. 

CLIMATE STATION STATISTICS

Long-term Statistics for October
(Climatological reference period: 1981 – 2010)

Historical Extremes for October
(Rainfall since 1869 and temperature since 1929)

Singapore, 16 September 2019 – The prevailing Southwest Monsoon conditions in the region are forecast to persist for the rest of September 2019. During this period, the low level winds are expected to blow from the southeast or south, and on occasions, shift to blow from the southwest.

2          In the coming fortnight, dry air from high pressure systems over northern Australia are forecast to continue blowing over the southern Southeast Asia region, including Singapore. Persisting cooler sea surface temperatures  over the tropical eastern Indian Ocean[1] (positive Indian Ocean Dipole) will also suppress raincloud formation over the surrounding region. Additionally, with the monsoon rain band forecast to remain over northern Southeast Asia, away from Singapore, the prevailing dry weather is expected to continue into the second fortnight of the month.

3          In the last week of the month, there could be some brief respite as the high pressure system over northern Australia is expected to weaken, and with strong solar daytime heating of land areas, localised short-duration showers can be expected in the afternoon on a few days.

4          The rainfall for September 2019 is likely to be significantly below September’s climatological normal of 185.4mm.  September 2019 is thus likely to be the third consecutive month, following July and August 2019, with more than 40% below-normal monthly rainfall, giving rise to a potential rainfall deficit [2] situation. The total rainfall for July and August 2019 recorded at rainfall stations across the island with long term records was 51% and 82% below normal respectively. The last occurrence of a rainfall deficit situation in Singapore was in 2014 from January to March, where the average rainfall total for each month across Singapore was 67%, 89% and 50% below the month’s normal.

5          For the rest of September 2019, the prevailing warm conditions are forecast to continue. The daily temperature is expected to range between 26°C and 34°C on most days, with highs exceeding 35°C on a few days. The nights are expected to be warm with daily minimum temperatures of 27°C or more on some days. Night-time temperatures in the southern and eastern coastal areas could be warmer, at around 28°C, when prevailing winds blowing from the southeast bring warm and humid air from the surrounding seas.

6          The prevailing dry weather over southern Southeast Asia is expected to persist in the coming fortnight. Hotspots with smoke plumes continue to be observed over parts of Sumatra and Kalimantan. Singapore may continue to experience hazy conditions during the fortnight, depending on the wind conditions and the proximity and extent of the fires.

7         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 15 September 2019)

8          During the first fortnight of September 2019, Southwest Monsoon conditions continued to prevail, and the low level winds blew from the southeast or southwest.

9          In the first half of September 2019, the weather over Singapore was generally dry and warm. These conditions were due to suppressed raincloud formation arising from dry air that was blown to the southern Southeast Asia region from high pressure systems over northern Australia, coupled with the persisting cooler sea surface temperature over the tropical Indian Ocean. There were however a few days when brief showers fell over Singapore. In particular, on 4 September 2019, the thundery showers over many parts of the island were due to convergence of winds over Singapore and the surrounding vicinity. Rainfall was heaviest over the western part of the island, and the highest daily total rainfall recorded that day was 93.3mm at Jurong West.

10        In the second week of September 2019, smoke haze from hotspots in central and southern Sumatra were blown in by the prevailing winds to Singapore. This brought slightly hazy conditions to the island with the air quality in the high end of the Moderate range on most days of the week. A sudden deterioration in the haze situation on 14 September 2019 caused the 24-hour PSI to dip into the Unhealthy range.

11        The first half of September 2019 was warm, with daily maximum temperatures reaching at least 34.0°C on 9 days (as at 13 September 19). The highest daily maximum temperature of 34.8°C was recorded on 12 September 2019 over the northern part of the island at Admiralty.

12        Significantly well-below-average rainfall was recorded across the island in September 2019. The lowest anomaly of 100% below-average was recorded at a few stations in the eastern part of the island.

[1] The Indian Ocean Dipole (IOD) refers to the sustained change to the difference between sea surface temperatures (SSTs) of the tropical western and eastern Indian Ocean. The IOD varies between three phases – positive, negative and neutral. A positive (negative) phase occurs when cooler (warmer) SSTs develop in the eastern Indian Ocean, resulting in below (above) normal rainfall in the eastern Indian Ocean and the surrounding region. More information on the IOD can be found at https://www.weather.gov.sg/LEARN_climate/.

[2] A rainfall deficit refers to a period of at least 3 consecutive months with monthly rainfall more than 40% below the climatological rainfall, averaged over the rainfall stations with long term records across the island. 

CLIMATE STATION STATISTICS

Long-term Statistics for September
(Climatological reference period: 1981 – 2010)

Historical Extremes for September
(Rainfall since 1869 and temperature since 1929)

August 2019 likely the driest and warmest August on record

Singapore, 30 August 2019 – The prevailing Southwest Monsoon conditions in the region are forecast to persist in the first fortnight of September 2019.  During the period, the low level winds are forecast to blow mostly from the southeast or southwest, and may on brief occasions, shift to blow from the west.

2          During the fortnight, the monsoon rain band is forecast to remain over the northern Southeast Asia region, away from Singapore. Under the influence of cooler sea surface temperatures over the tropical eastern Indian Ocean, dry weather is forecast to prevail over Singapore and the surrounding region in the first fortnight of September 2019. However, localised short-duration thundery showers can still be expected on four or five days between the late morning and early afternoon. In addition, Sumatra squalls are forecast to bring thundery showers and gusty winds on one or two mornings. The rainfall in the first fortnight of September is likely to be significantly below normal.

3          The first fortnight of September 2019 is expected to be as warm as the last month. On most days, the daily temperature is forecast to range between 26°C and 34°C, with highs of around 35°C on a few days. Warm nights with daily minimum temperatures above 26°C are expected on some days, reaching around 28°C in the southern and eastern coastal areas when prevailing winds blowing from the southeast bring in warm and humid air from the surrounding seas.

4          The weather in the surrounding region is also forecast to be dry in the coming weeks. Hotspots with smoke plumes continue to be observed in parts of Sumatra and Kalimantan. Depending on the direction of the prevailing winds and the proximity and extent of the fires, Singapore may experience occasional haze.

5         For updates of the daily weather and haze situation, please visit the MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, MSS’ Weather@SG app, and the haze microsite (www.haze.gov.sg).

REVIEW (1 – 29 August 2019)

6          In August 2019, Southwest Monsoon conditions continued to persist with the low level winds blowing from the southeast or southwest.

7          The weather over Singapore and the surrounding region has been dry since late July 2019. Between 31 July and 16 August 2019, Singapore experienced a dry spell[1] of 17  consecutive days. The dry spell eased on 17 August 2019 when showers fell over many parts of the island that day. The highest rainfall recorded on 17 August 2019 was 13.0 mm around the city area. The extended dry weather can be attributed to an intrusion of dry air from high pressure systems over northern Australia coupled with suppressed raincloud formation due to cooler sea surface temperatures over the tropical eastern Indian Ocean (positive phase of Indian Ocean Dipole (IOD)[2]).

8          For the rest of August 2019, it was dry and warm on most days with a few days of thundery showers which brought some welcome relief from the hot and humid conditions. On 26 August 2019, strong solar heating of land areas coupled with large-scale wind convergence brought widespread moderate to heavy thundery showers over many parts of the island. The highest daily total rainfall recorded that day was 78.4 mm at Yishun. At the climate station in Changi, the total rainfall recorded for August 2019 was 11.8 mm (as of 29 August 2019), lower than the August record low rainfall of 18.0 mm in 1888. August 2019 is thus on track to be the driest August in Singapore since rainfall records began in 1869.

9          August 2019 was also a warm month, with daily maximum temperatures reaching at least 34°C on 13 days (as at 29 August 2019). The highest temperature of 34.8°C was recorded at Marina Barrage on 23 August 2019. The nights were generally warm with daily minimum temperatures above 26°C recorded over most parts of Singapore. There were a few nights in the southern and eastern coastal areas of the island where the minimum temperature was around 28°C.

10        At the climate station in Changi, the mean monthly temperature for the month is 29.1°C (as at 29 August 2019). This is 0.2°C above the highest ever mean monthly temperature for August, recorded in 2016. August 2019 is thus likely to be the warmest ever August in Singapore since temperature records started in 1929. For the month to date, the average minimum temperature for August 2019 was 27.1°C, 0.9°C above the August record high temperature of 26.2°C in 2016.

11        Significantly well-below-average rainfall was recorded across the island in August 2019. The lowest anomaly of 98% below-average was recorded at Paya Lebar.

[1] A dry spell is defined as a period of at least 15 consecutive days with daily total rainfall of less than 1.0 mm, averaged over rainfall stations with long-term records across the island.

[2] The Indian Ocean Dipole (IOD) refers to the sustained change to the difference between sea surface temperatures (SSTs) of the tropical western and eastern Indian Ocean. The IOD varies between three phases – positive, negative and neutral. A positive (negative) phase occurs when cooler (warmer) SSTs develop in the eastern Indian Ocean, resulting in below (above) normal rainfall in the eastern Indian Ocean and the surrounding region. More information on the IOD can be found at https://www.weather.gov.sg/LEARN_climate/.

CLIMATE STATION STATISTICS

Long-term Statistics for September
(Climatological reference period: 1981 – 2010)

Historical Extremes for September
(Rainfall since 1869 and temperature since 1929)

Singapore, 16 August 2019 – The prevailing Southwest Monsoon conditions are forecast to persist over Singapore and the surrounding region for the rest of August 2019, and extend into October 2019. During this period, the prevailing winds are forecast to blow mostly from the southeast or southwest.

2          In the second fortnight of August 2019, dry conditions are forecast on most days as dry air from high pressure systems over northern Australia extends to the equatorial region. Singapore has been experiencing a dry spell [1] since 31 July 2019. With thundery showers expected in the late morning and early afternoon on four or five days toward the last week of August 2019, the showers will bring some respite to the current dry spell. On some days, breezy conditions can be expected due to the occasional strengthening of winds over the equatorial region. Rainfall for the month is expected to be significantly below normal.

3         The rest of August 2019 is expected to be warm. On most days, the daily temperature is forecast to range between 26°C and 34°C, with highs of around 35°C on a few days. The minimum temperature on some nights can hover around 28°C, when prevailing winds blowing from the southeast bring in warm and humid air from the surrounding seas.

4         The dry weather in the surrounding region is forecast to persist. Hotspots with smoke plumes continue to be observed in various parts of Sumatra and Kalimantan. Depending on the direction of the prevailing winds and location of the fires, Singapore may experience occasional haze.

5         For updates of the daily weather forecast, please visit our MSS website (https://www.weather.gov.sg), NEA website (www.nea.gov.sg), or download the myENV app, or the MSS’ Weather@SG app.

REVIEW (1 – 15 August 2019)

6          During the first fortnight of August 2019, Southwest Monsoon conditions prevailed with the low level winds blowing from the southeast or southwest.

7          The dry weather prevailing in Singapore and the surrounding region since late July 2019 persisted in the first half of August 2019. Singapore experienced a dry spell [1] of 16  consecutive days between 31 July and 15 August 2019. While brief localised showers fell on some days, most parts of Singapore were dry with about 90% of all stations island-wide recording daily rainfall below 0.2 mm. The last recorded dry spell in Singapore lasted 27 days from 17 February to 15 March 2014. The extended dry weather can be attributed to an intrusion of dry air from northern Australia coupled with suppressed raincloud formation due to cooler sea surface temperatures over the tropical eastern Indian Ocean (positive phase of Indian Ocean Dipole (IOD)[2]).

8          The dry weather also contributed to a very warm first half of August 2019, with the daily maximum temperature ranging between 31.9°C and 34.5°C. The highest temperature of 34.5°C was recorded at Marina Barrage on 13 August 2019. The nights were generally warm with daily minimum temperatures above 26°C recorded over most parts of Singapore. There were a few nights where the temperature remained around 28°C in the southern and eastern coastal areas of Singapore.

9          In the first fortnight of August 2019, significantly below-average rainfall was recorded at all stations across the island. The rainfall anomaly was close to 100% below-average for many parts of Singapore.

[1] A dry spell is defined as a period of at least 15 consecutive days with daily total rainfall of less than 1.0 mm, averaged over rainfall stations with long-term records across the island.

[2] The Indian Ocean Dipole (IOD) refers to the sustained change to the difference between sea surface temperatures (SSTs) of the tropical western and eastern Indian Ocean. The IOD varies between three phases – positive, negative and neutral. A positive (negative) phase occurs when cooler (warmer) SSTs develop in the eastern Indian Ocean, resulting in below (above) normal rainfall in the eastern Indian Ocean and the surrounding region. More information on the IOD can be found at https://www.weather.gov.sg/LEARN_climate/.

CLIMATE STATION STATISTICS

Long-term Statistics for August
(Climatological reference period: 1981 – 2010)

Historical Extremes for August
(Rainfall since 1869 and temperature since 1929)

Singapore, 2 August 2019 – The National Environment Agency’s (NEA) Meteorological Service Singapore (MSS) is forecasting drier-than-normal weather conditions in Singapore and the surrounding region, including Sumatra and Kalimantan, in the coming weeks. In recent days, persistent hotspot activities with smoke plumes have been observed in Riau and Jambi provinces in Sumatra and southern parts of Kalimantan. These conditions can lead to an escalation of hotspot activities and an increase in the risk of transboundary haze occurrence in Singapore and the surrounding region.

2      Since early July 2019, dry weather has been persisting over southern Sumatra and Kalimantan. Drier weather can be expected in the next three months (August to October), with monthly rainfall of up to 60% below average.

3     Singapore has likewise been experiencing dry and warm weather in recent weeks. The total rainfall recorded for July 2019 at the climate station in Changi is 92% below the long term average, breaking the record set in 1997 for the driest July in Singapore. July 2019 is also Singapore’s second warmest July on record, with an average temperature of 29.0°C.

Impact of the Indian Ocean Dipole

4     Neutral conditions (neither El Nino nor La Nina) currently prevail in the tropical Pacific Ocean, and are forecast to persist for the rest of the year. A key climate driver influencing the rainfall over Singapore and the surrounding region over the next few months is the Indian Ocean Dipole (IOD), which refers to the sustained change to the difference between sea surface temperatures (SSTs) of the tropical western and eastern Indian Ocean. The IOD varies between three phases – positive, negative and neutral. A positive (negative) phase occurs when cooler (warmer) SSTs develop in the eastern Indian Ocean, resulting in below (above) normal rainfall in the eastern Indian Ocean and the surrounding region. Each phase occurs every three to five years on average and typically lasts about six months.

5     The IOD is currently in its positive phase, which leads to drier weather over the areas adjacent to the eastern Indian Ocean, including Sumatra, Malaysia and Singapore. Major climate centres are predicting that the positive phase of the IOD is expected to persist over the coming months.

Risk of Transboundary Haze

6     Singapore may experience occasional occurrences of transboundary haze during the next few weeks to months. The likelihood of haze affecting Singapore is dependent on factors such as the proximity and extent of the fires, the direction and strength of the prevailing winds, and the incidence of rain.

7     MSS will continue to closely monitor the regional weather and haze situation, and provide updates when necessary. Updates on haze information are available on the MSS website at https://www.weather.gov.sg/warning-haze-satellite-image/.