Subseasonal Weather Outlook and Review

1.1    Northeast Monsoon conditions prevailed in January 2015. In the northern ASEAN region, dry weather conditions continued to affect the Mekong Sub-region of Cambodia, Lao PDR, Myanmar, northern Thailand and Vietnam. In mid-January 2015, the monsoon rain-belt had moved south of the equator marking the onset of the dry phase of the Northeast Monsoon season in the southern ASEAN region. Generally cooler, drier and windy weather conditions were experienced in Sumatra, Peninsula Malaysia and Singapore while wet weather conditions were felt in Kalimantan, the Java islands as well as parts of Sabah and Sarawak in Malaysia. In the last week of January 2015, a monsoon surge brought heavy rains and caused floods in the states of Sabah and Sarawak in Malaysia.

1.2    On 13 January 2015, Typhoon “Mekkhala” developed over the Western Pacific Ocean, and continued its westward track afecting the eastern part of Luzon and Visayas in the Philippines a few days later. Typhoon “Mekkhala” made landfall near eastern Samar, the Philippines on 17 January 2015, and weakened rapidly into a tropical depression as it moved north-eastwards, dissipating over water on 21 January 2015 away from Luzon Islands.

1.3    In January 2015, less than 75% of normal rainfall was received in most parts of northern ASEAN except in northern Thailand and southern parts of Vietnam, where more than 125% of normal rainfall was received. In most parts of the southern ASEAN region, less than 100% of normal rainfall was received. The regional rainfall distribution for January 2015 is shown in Fig. 1A.

2.1    In January 2015, the dry weather conditions led to an escalation of hotspot activities in the northern ASEAN region where scattered to widespread hotspots were observed on most days, in particular in Cambodia, central and northeastern Thailand and Lao PDR. Slight to moderate smoke haze was also observed on several occasions during the period.

2.2    In the southern ASEAN region, hotspot activities were mostly subdued by cooler and occasionally windy conditions. During brief periods of drier weather, sporadic hotspots were observed over central Sumatra and Peninsular Malaysia. Satellite images depicting some of the hotspot activities over the ASEAN region in February 2015 are shown in Figs. 2A to 2E.

1.1    Northeast Monsoon conditions prevailed in January 2015. In the northern ASEAN region, dry weather conditions continued to affect the Mekong Sub-region of Cambodia, Lao PDR, Myanmar, northern Thailand and Vietnam. In mid-January 2015, the monsoon rain-belt had moved south of the equator marking the onset of the dry phase of the Northeast Monsoon season in the southern ASEAN region. Generally cooler, drier and windy weather conditions were experienced in Sumatra, Peninsula Malaysia and Singapore while wet weather conditions were felt in Kalimantan, the Java islands as well as parts of Sabah and Sarawak in Malaysia. In the last week of January 2015, a monsoon surge brought heavy rains and caused floods in the states of Sabah and Sarawak in Malaysia.

1.2    On 13 January 2015, Typhoon “Mekkhala” developed over the Western Pacific Ocean, and continued its westward track afecting the eastern part of Luzon and Visayas in the Philippines a few days later. Typhoon “Mekkhala” made landfall near eastern Samar, the Philippines on 17 January 2015, and weakened rapidly into a tropical depression as it moved north-eastwards, dissipating over water on 21 January 2015 away from Luzon Islands.

1.3    In January 2015, less than 75% of normal rainfall was received in most parts of northern ASEAN except in northern Thailand and southern parts of Vietnam, where more than 125% of normal rainfall was received. In most parts of the southern ASEAN region, less than 100% of normal rainfall was received. The regional rainfall distribution for January 2015 is shown in Fig. 1A.

2.1    In January 2015, the dry weather conditions led to an escalation of hotspot activities in the northern ASEAN region where scattered to widespread hotspots were observed on most days, in particular in Cambodia, central and northeastern Thailand and Lao PDR. Slight to moderate smoke haze was also observed on several occasions during the period.

2.2    In the southern ASEAN region, hotspot activities were mostly subdued by cooler and occasionally windy conditions. During brief periods of drier weather, sporadic hotspots were observed over central Sumatra and Peninsular Malaysia. Satellite images depicting some of the hotspot activities over the ASEAN region in February 2015 are shown in Figs. 2A to 2E.