Monthly Archives: March 2015

March 31, 2015

Moderate Haze during Prolonged Dry Spells in late Northeast Monsoon 2014

The prolonged dry spell experienced in Singapore during late phase of the Northeast Monsoon also affected the surrounding regions and resulted in an increase in hotspot activities in central Sumatra and Malaysia, including southern Johore. The prevailing north-easterly winds then blew the smoke haze from the hotspots in southern Johor towards Singapore on several days from 7 to 15 March. PSI readings hit the Moderate range during this period.

Hotspots and smoke/haze situation on 11 March 2014.

Smoke haze from southern Johore blown towards Singapore.

March 21, 2015

Haze Situation Update (21 March 2015)

Singapore, 21 March 2015 – Hazy conditions continue to affect Singapore today. The PM_2.5levels are slightly elevated in most regions of Singapore this afternoon. At 6pm, the 24-hr PSI was 72-82, in the Moderate range, while the 1-hr PM_2.5concentration was 32-42 ug/m³. There were thundery showers in the northern and central parts of Singapore in the late afternoon.

2The haziness is likely due to an accumulation of particulate matter in the atmosphere under light wind conditions. Burning activities in the region could have contributed to an increased concentration of particulate matter.

3The current hazy conditions are expected to persist for the rest of today. For tomorrow, slight haziness under light wind conditions can still be expected, and thundery showers are forecast in the late afternoon and evening. The 24-hr PSI for Singapore is expected to be in the Moderate range.

4The health impact of haze is dependent on one’s health status, the PSI level, and the length and intensity of outdoor activity. Reducing outdoor activities and physical exertion can help limit the ill effects from haze exposure. Persons who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention. Given the air quality forecast for the next 24 hours, everyone can continue with normal activities.

5For updates, visit our NEA website (www.nea.gov.sg), the haze microsite (www.haze.gov.sg), or follow us on NEA Facebook (www.facebook.com/NEASingapore) and NEA Twitter (@NEAsg).

– End –

March 20, 2015

Haze Situation Update (20 March 2015)

Singapore, 20 March 2015 – It has been hazy in Singapore today. The PM_2.5levels are elevated in most regions of Singapore. At 8pm, the 24-hr PSI was 74-86, in the Moderate range, while the 3-hr PSI was 99, and the 1-hr PM_2.5concentration was 16-54 ug/m³.

2The haziness is likely due to an accumulation of increased particulate matter in the atmosphere under light wind conditions throughout today. Burning activities in the Northern Asean region, Peninsular Malaysia and Sumatra could have contributed to the increased concentration of particulate matter.

3The current hazy conditions are expected to persist for the rest of today. For tomorrow, the prevailing winds are expected to be light and variable in direction, and hazy conditions can still be expected. The 24-hr PSI for Singapore is expected to be in the Moderate range.

5For updates, visit our NEA website (www.nea.gov.sg), the haze microsite (www.haze.gov.sg), or follow us on NEA Facebook (www.facebook.com/NEASingapore) and NEA Twitter (@NEAsg).

– End –

March 13, 2015

Prolonged Dry Spells in late Northeast Monsoon 2014

The dry phase of the Northeast Monsoon, typically onsets in late January or February but in 2014, the onset was earlier in mid-January. In the 2014 Northeast Monsoon season, Singapore experienced two 27-day dry spells* during the period from 13 January to 8 February, and again from 17 February to 15 March. Both dry spells are the longest recorded on records since the 1960s, breaking the earlier record of 18 days in 2008.

One possible reason for the prolonged dry condition could be the source of the dry air mass over Singapore and the surrounding region. In the past dry phases of the Northeast Monsoon, air usually originates from the West Pacific maritime region. The air would be less dry because it would “collect” moisture as it moves across the sea areas towards Singapore. For 2014, the air mass over the region originated from the dry continental land mass.

The rainfall in February 2014 has set a new record for the driest month since 1869, with the rainfall total recorded as 0.2 mm at Changi climate station. This falls well below the previous record of 6.3 mm recorded in February 2010. February 2014 was also the windiest month in the last 30 years. The average daily wind speed for the month recorded at Changi climate station was 13.3 km/h, compared to the February average wind speed of 8.8 km/h. This too broke the previous record of 12.5 km/h in January 1985.

*A dry spell is defined as a period of at least 15 consecutive days with daily rainfall total of less than 1mm in many parts of the island.

The 5 longest dry spells (to date) since 1980 are:

Year	Duration (days)	Dry spell periods
2014	27	13 Jan – 8 Feb
2014	27	17 Feb – 15 Mar
2008	18	04 Feb – 21 Feb
2005	17	18 Jan – 3 Feb
1987	17	06 Feb – 22 Feb

Based on our wind records of our climate station since 1984, the 5 strongest recorded average wind speeds are:

Year	Month	Average Wind Speed (km/h)
2014	Feb	13.3
1985	Jan	12.5
1987	Feb	12.4
1990	Feb	12.3
1989	Feb	12.0

Thunderstorms with Hail in Singapore

An intense thunderstorm in the afternoon over western Singapore brought hailstones the size of small pebbles to the Bukit Batok area on 25 June 2013. The thunderstorm developed following strong solar heating and convergence of winds over western Singapore. Moderate rainfall of 31.8 mm over half an hour was recorded at Corporation Road between 2.50pm and 3.20pm.

The intense thunderstorm (in red and pink colours) as detected by weather radar and hailstones sighted at Bukit Batok around 3pm on 25 June 2013.

In 2014, hail was observed during an intense thunderstorm event on 14 October around the Turf Club Road area.

The previous reported occurrence of hail in Singapore was on 12 September 2009.

Severe Transboundary Smoke Haze during Southwest Monsoon 2013

In the second week of June 2013, hotspot activities escalated in central Sumatra as a result of the relatively dry atmospheric conditions in the region. Westerly winds over the equatorial Indonesia then blew the moderate to dense smoke haze in central Sumatra towards Malaysia and Singapore. Slightly hazy conditions was experienced in Singapore on 13 June 2013, but the condition deteriorated rapidly on 17 – 18 June 2013, with the 24-hr PSI readings breaching the Unhealthy and Very Unhealthy levels within the next few days. The 3-hr PSI reached a record high of 401 on 21 June 2013, and the 24-hr PSI reached a record high of 246 on 22 June 2013, making this the worst transboundary smoke haze occurrence ever experienced in Singapore.

The smoke haze situations on 18 – 19 Jun 2013 were shown in the following NOAA-18 satellite images.

A change in wind direction on 25 June 2013 then brought an end to the haze in Singapore.

The unseasonal westerly winds were partly attributable to the presence of an unusually strong low pressure area to the southwest of Sumatra in Indian Ocean and also to the presence of the two tropical storms near Philippines during the period.

Northeast Monsoon Surges 2013

A moderate Northeast Monsoon surge affected the region on 18 – 22 January 2013 during the wet phase of the Northeast Monsoon season. The surge was due to the strengthening of winds over the South China Sea. The rain was prolonged and widespread, intermittent and heavy at times with occasional windy conditions. The surge was most intense on 19 January, with the highest total rainfall of 134.7 mm recorded at Changi area.

Another surge occurred quite late into the Northeast Monsoon on 12 – 14 February 2013. This surge was weaker and brought moderate to heavy thunderstorms over Singapore on 14 February, with the highest rainfall total of 117.6 mm recorded at Seletar area.

March 12, 2015

Warm Temperature in March and April 2013

Singapore experienced warm conditions in March and April 2013, due to the weakening of the winds coupled with strong convective heating in the day, which is typical during this time of the year as the sun is almost overhead at the equator and the Northeast Monsoon transitions into the Inter-Monsoon season. During this period, the winds are weak and variable, and hot afternoons are common.

The highest daytime maximum temperatures for March and April 2013 are 33.8 °C and 36.2 °C, recorded on 30 March and 16 April respectively.

The highest temperature ever recorded at our climate station in Changi is 36.0 deg C on 26 Mar 1998. The highest temperature recorded at any station in Singapore so far is 37.0 deg C on 17 April 1983.