Southeast Asia & the Pacific: Intense surplus forecast in Java & C Vietnam

21 June 2022

THE BIG PICTURE
The 12-month forecast through February 2023 indicates surpluses of varying intensity in several regions of Southeast Asia and many regions of the Pacific, though deficits are forecast in Sumatra and Papua New Guinea.

In Myanmar, surpluses of varying intensity are forecast throughout the Irrawaddy River Basin and in Peninsular Myanmar, with some transitional conditions (pink/purple) in the center of the nation near Mandalay. Near-normal water conditions are forecast for most of Thailand though surpluses are expected south of the Mun River along the Cambodian border and in much of Peninsular Thailand. Surpluses will be widespread in northern Laos and northern Vietnam, reaching extreme to exceptional intensity in Vietnam’s northeast near the Chinese border. Moderate surpluses are expected in the South Central Coast region and Central Highlands, leading into Cambodia.

In the Philippines, moderate surpluses are predicted for northern Luzon, but more intense anomalies are expected in the central islands, Mindanao’s northern half, and much of Palawan.

Though normal water conditions are forecast for most of Malaysian Borneo, moderate deficits are expected south of the Kuching metropolitan area and surpluses are expected in the northeast. The remainder of Borneo can expect surpluses as well. Surpluses are also forecast throughout much of Indonesia and the small island nations in the region. Anomalies will be exceptional in Java, Flores Island, the tip of Sulawesi’s northern arm, and several regions along Papua, Indonesia’s south coast. Sumatra is forecast to experience moderate to extreme deficits from Medan in the north through the center of the island.

Deficits are also forecast in Papua New Guinea along its north coast, in western coastal regions on the Gulf of Papua, and in the Owen Stanley Range in the Bird’s Tail Peninsula (Papuan Peninsula). Anomalies will be intense on the north shore and along the Gulf. Intense deficits are also forecast for New Britain and the Solomon Islands.

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

The forecast through August indicates that surpluses will shrink and downgrade in Southeast Asia but remain widespread, particularly in Vietnam. Anomalies are forecast from northern Vietnam well into the South Central Coast region with extreme to exceptional surpluses north of Hanoi and exceptional surpluses around Da Nang. Surpluses will persist in northern Laos; and in Thailand’s northwest, from the Mun River into Cambodia, and from Peninsular Thailand into Malaysia. In Myanmar, mixed conditions are forecast in the Irrawaddy Watershed with surpluses more prevalent in the nation’s far north and east. Surpluses are expected in the Philippines. Deficits are forecast around Medan, Sumatra and in the southwest; in Indonesian Borneo’s northern tip; and in New Guinea along the north coast, in New Britain, the Papuan Peninsula, and pockets on the west coast of the Gulf of Papua. Anomalies will be intense on Papua New Guinea’s (PNG) central north coast and in New Britain and the Solomons. Elsewhere in Indonesia and the Pacific, surpluses are expected in southwestern Sumatra, Java, much of Indonesian Borneo, the Lesser Sundas and Sulawesi, and from Papua, Indonesia’s Arafura Sea Coast well inland and into PNG. Anomalies will be exceptional in Java and Flores Island.

From September through November, surpluses will shrink considerably in Southeast Asia with moderate anomalies persisting in Vietnam’s South Central Coast and Central Highlands. Moderate deficits are expected in northwestern Myanmar and Vietnam’s northwestern tip, and severe deficits in Peninsular Malaysia. Deficits in Sumatra will increase and become intense while those in New Guinea downgrade. A few pockets of surplus are forecast in the Philippines, and widespread surpluses of varying intensity in Indonesian Borneo, Java and the Lesser Sunda Islands, Sulawesi, the Malukus, and Papua into PNG.

The forecast for the final months – December 2022 through February 2023 – indicates deficits in Sumatra, the Malay Peninsula, pockets of Borneo and Myanmar, and northern Laos. Surpluses are forecast in the Central Highlands of Vietnam, a few pockets in the Philippines, the Lesser Sundas and Malukus, and pockets in coastal New Guinea.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
Incessant rainfall produced flooding and landslides in several regions of Indonesia. In West Sumatra, the Lembah Anai Waterfall in Padang surged, creating a spectacular display at the tourist attraction, flooding streets and blocking traffic. In mid-June, the Moko River in Central Sulawesi overflowed, inundating 150 homes. Residential areas in Surabaya, East Java also flooded as did commercial streets with floodwaters reaching 50 centimeters (19.7 inches).

A downpour in late May turned the streets of Hanoi, Vietnam into raging rivers after record-breaking rainfall dumped 138 millimeters (5.4 inches) on the capital while several other districts received as much as 170 millimeters (6.7 inches). A repeat occurred in mid-June, leaving many cars stalled in the Hanoi’s submerged streets. Three people died in Vinh Phuc Province in northern Vietnam after a wall collapsed during post-storm clean-up in late May.

Phnom Penh, Cambodia’s capital and home to over two million people, also saw record rainfall that flooded major transit routes leaving many unpassable and damaged retail establishments.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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