East-Asia

East Asia’s wind and weather is broadly determined by the Asian monsoon climate. Low pressure over the continent dominates in summer as intense sunshine creates rising air above the landmass. A humid air-mass is drawn between this heat low and the sub-tropical Pacific High, introducing a weak southerly airflow into the region. In rainy season, the South China Sea’s tropical zones receive ten times more rain than the rest of the year. This is the hottest time of year with temperatures over 30°C. The water also warms up to 28-30°C, enabling typhoons to build over Pacific waters near the equator from July to November and travel north-west – 20 to 30 rage from the Philippines up to Japan every year!

The system reverses in autumn, as the continent from Siberia to the Himalayas cools, air pressure increases over central Asia, inverting the pressure differential and spreading a NE Monsoon south down the Chinese coast. It blows most solidly where regional strengthening helps out, like the venturi effect in the Strait of Taiwan (Penghu Islands), or the thermal and barrier effects in Southern Vietnam. The island of Hainan in southern China and the Philippines get decent wind from November to March. The Gulf of Thailand is also touched by the NE Monsoon, although it’s a lot weaker. At least the Thai-Malay Peninsula can occasionally expect sailable SW wind in summer.

The Indonesian regions south of the equator owe their conditions more to Indian Ocean weather systems. Bali lies within the influence of the SE trades from May to September, they’re even stronger further east in Sumbawa but the season starts later as Hu’u Bay needs a healthy southerly component. Bali and Sumbawa also enjoy by far the best swell, from April to October scoring the same quality Roaring Forties groundswell as Mauritius, La Réunion, and the Cocos Islands in the Indian Ocean; long period and groomed into clean sets on their long voyage.

South China Sea regions have to make do with windswell – although it can be surprisingly big at exposed South Vietnam spots and the particularly windy waters of Taiwan. The Gulf of Thailand and most of the Philippine Visaya Islands are well sheltered, and therefore classic flat-water destinations.

While the regions below 20° North remain tropically warm year-round, north of the Tropic of Cancer experiences the marked seasonal temperature differentials associated with continental eastern seaboards. Admittedly, South Korea and Japan both score the southerly summer and northerly winter monsoons, but the air coming straight off Siberia in winter can be bitterly cold. Hence summer’s generally weaker winds are best for kiting or windsurfing on South Korea’s East Coast & Jejudo island. However, Japan enjoys the best of both worlds in the transitional months thanks to the warm Kuroshio Current keeping water temperatures above 14°C on the east coast of Chiba Prefecture. The water’s never cooler than 17°C South of Tokyo, allowing the locals to ride their beloved Omaezaki all winter long. Winter’s also wave season as low pressure storms ravage the North Pacific. But any swell sent Japan’s way has to come off their backsides as the majority is blown easterly. Local groundswells are hence short-lived, and only big ones might make it all the way down to the east coast of the Philippines. Japan’s summer is basically poor for wind and swell, unless one of about 25 annual typhoons tracks just right. With the world’s highest typhoon risk, these magic swells reach Japan quite regularly – but suitable wind is far less likely, and even then it’s a fine line between exhilarating and devastating!

An irregular semi-diurnal tide prevails in East Asia, with both a small and large high tide every day. In the virtually enclosed waters of the Gulf of Thailand and South China Sea, a maximum tidal range of less than a metre has negligible effect. In contrast, up to 2m or more occurs in Japan and the Andaman, East China, and Yellow Seas. Small tides of just a metre are still noticeable on the reefs off Bali’s east coast, while the funnel-shaped Hu’u Bay in neighbouring Sumbawa suffers a tidal range of many metres making timing key on sensitive reefs like Lakey’s.