Southeast Asia & the Pacific: Intense water deficits to persist in W Cambodia

29 November 2017

THE BIG PICTURE
The 12-month map (below) indicates intense surpluses in western and eastern Myanmar and the southern portion of the Irrawaddy River, Laos, eastern Cambodia, much of Vietnam, and Negros Island, Philippines. Surpluses of lesser intensity are forecast for the central Philippines and scattered pockets from northwestern Indonesian Borneo through western Papua.

A large block of exceptional water deficit is forecast for western Cambodia. Moderate to exceptional deficits are expected in the Highlands of central Papua New Guinea, and deficits of lesser severity are forecast for Malaysia, southern Sumatra, and scattered pockets around the Java Sea.

IMPACTS
The strongest typhoon to hit southern Vietnam in 16 years, Typhoon Damrey, struck in early November, killing over 100 people, injuring 200, damaging at least 80,000 homes, and affecting around 4 million people in 14 provinces. About 61,750 acres of agricultural land were inundated and 25,000 fishing cages destroyed. Before reaching Vietnam, Damrey dumped 300mm (12 inches) of rainfall on Visayas and Luzon in the Philippines, resulting in a landslide that claimed two lives.

Later in November, southern Vietnam battled tropical storm Kirogi as it dropped another 182mm (about 7 inches) of rain in some cities, disrupting salt farm operations in the southern province of Ninh Thuane. Thailand, too, was flooded by Kirogi, when heavy rain caused the Phetchaburi River to overflow into the town of Petchaburi and its major highway.

The Penang State government in Malaysia is anticipating around 100,000 applications for federal flood relief due to heavy rains associated with Typhoon Damrey. The resulting flooding has been called the state’s worst, causing at least seven deaths and extensive road and property damage. The severe need comes two months after 7,000 payouts were made following floods in September.

FORECAST BREAKDOWN
The 3-month maps (below) show the evolving conditions in more detail.

Clearly indicated in the map progression is a gradual transition in the region from predominantly surplus conditions to deficit. Notably, Cambodia stands out in dark red indicating intense deficit conditions in prior months as well as throughout much of the forecast period.

The November through January forecast shows a significant retreat of surplus conditions in Malaysia, Indonesia, Philippines, and Papua, with moderate surpluses indicated for Sumatra and slightly more intense surpluses lingering in Negros, Philippines. Conditions in Southeast Asia, however, look similar to the prior three months. In Myanmar exceptional surpluses will persist in the west and increase in the east. In Thailand surpluses will diminish overall, with some central regions returning to near-normal conditions. Exceptional surpluses will continue in northern Laos while surpluses in the south will moderate somewhat. Intense surpluses remain in the forecast for northern Vietnam and moderate to severe surpluses will emerge throughout much of the south. As Southeast Asia and the Pacific begin a transition to deficits, some primarily moderate deficits will emerge in southern Thailand and in small pockets around the Java Sea. Deficits in Papua New Guinea will diminish.

During the next quarter, February through April, the transition to deficits becomes more apparent as moderate to extreme deficits emerge in Malaysia and Indonesia. Note, also, the pinks and purples in Southeast Asia, indicating conditions of both surplus and deficit as deficits emerge. Severe to exceptional surpluses remain in the forecast during this period for northwestern and eastern Myanmar, Laos, and northern Vietnam. Deficits in Papua New Guinea are expected to downgrade to mild.

After April the forecast indicates primarily deficit water conditions throughout the region with mild deficits in Southeast Asia and more intense deficits in Malaysia, Indonesia, and Papua.

(It should be noted that forecast skill declines with longer lead times.)

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