2018 Asia autumn forecast: Japan may face flood threats as drought builds from Ukraine to Kazakhstan
While the change of seasons will bring conditions typical of autumn in parts of Asia, there will be areas at risk for more extreme weather conditions ranging from floods to drought.
As El Niño strengthens, multiple typhoons are likely to curve toward Japan, while dryness builds in southeast Asia and drought increases over Russia's Volga Valley.
El Niño, the opposite of La Niña, is the warm phase of water temperatures over the tropical Pacific Ocean. During a strong El Niño, the jet stream can be significantly altered throughout the Northern Hemisphere.
Shifts in the jet stream can focus storms and heavy rain in some areas and at the same time contribute to drought in others.
Developing El Niño to impact typhoon development
El Niño is likely to have a significant impact on the western Pacific typhoon season.
"Even though the typhoon season got off to a slow start, we expect El Niño conditions this autumn to allow our projected average numbers of tropical storms, typhoons and super typhoons to be realized," according to AccuWeather Tropical Weather Expert Dan Kottlowski.
AccuWeather is projecting 27 tropical storms, 16 typhoons and 6 super typhoons through the end of December.
"In addition to some ground being made up in the coming weeks, as El Niño ramps up over the south-central and southeastern tropical Pacific Ocean, an eastward shift is likely in the main development area of tropical storms and typhoons this autumn," Kottlowski said.
The main development area is likely to be from the eastern Philippine Sea to east of the Mariana Islands.
As westerly winds increase during the autumn over northern Asia and the northern Pacific Ocean, the tropical storm and typhoon track often shifts eastward.
"The shift in development area, due to El Niño, combined with the routine increase in westerly winds is likely to keep most tropical storms and typhoons east of the Philippines and Taiwan," according to AccuWeather Lead Global Meteorologist Jason Nicholls.
However, Japan could become a regular target.
"Rounds of heavy rain and flooding will remain a big concern for Japan heading into the autumn," Nicholls said.
Deadly flooding occurred in the Hiroshima area of Japan during early July 2018. (AP Photo/Haruka Nuga)
Parts of Japan were hit hard by flooding rainfall, followed by extreme heat that set all-time high temperature records this summer.
Dryness to develop, perhaps escalate in Southeast Asia
In contrast to Japan, a limited number of tropical storms are forecast to affect the Philippines, Vietnam, Laos and Cambodia this autumn.
These areas are likely to turn drier than average during the middle to latter part of the autumn.
It is possible this drier-than-average pattern expands to much of Indonesia and Malaysia as the autumn progresses.
How dry conditions get in Southeast Asia later in the autumn and then the winter will depend on how strong El Niño becomes.
"If a strong El Niño develops it could get very dry across Southeast Asia, while a weak El Niño may just tone down showers and thunderstorms slightly," according to AccuWeather Meteorologist Adam Douty.
Monsoons to change hands in fairly typical fashion
As the southwest monsoon retreats from northwestern and central India early in the season, the northeast monsoon will slowly develop across southern India during October and ramp up during November and December.
"We expect rainfall to end up close to average for the northeast monsoon in southern India," Nicholls said.
Residents look at the remains of their road and vehicles damaged in flash floods following torrential rain in Jammu, India, Monday, Aug.13, 2018. India's southwest monsoon season runs from June to September. (AP Photo/Channi Anand)
"A repeat of the flooding of 2015 is not expected, but rainfall in the northeast monsoon should be greater than the past couple of years," Nicholls added.
Multiple cyclones possible in Bay of Bengal
As the southwest monsoon withdraws, there will be an increasing chance for tropical development over the northern Indian Ocean.
"The Bay of Bengal is favored for more tropical development, but a tropical depression or cyclone may also form over the Arabian Sea," Nicholls said.
"While there is a chance of multiple direct impacts along the coast of the Bay of Bengal, there is only a low chance any cyclone would have direct impact on the Arabian Peninsula."
Small portions along the coast of the Bay of Bengal could be hit with flooding and damaging winds from the depressions and cyclones.
Mediterranean storms to avoid Volga Valley region
Farther northwest, much of the Middle East will be drier and warmer than average through the autumn. However, the storm track is likely to become more active than usual from the Mediterranean coast and Turkey to Iran, Afghanistan and northern Pakistan during the latter part of the season.
"A large area of high pressure is likely to set up over eastern Europe, which may block storms and moisture from flowing into the area from the Black Sea to the Caspian Sea, including much of Russia's Volga Valley," AccuWeather Senior Meteorologist Eric Leister said.
"Instead, the storms will be forced farther south and across part of the Middle East," Leister said.
The pattern may bring a few opportunities for rainfall in parts of Lebanon, Israel and Jordan. But the pattern could escalate to the point where flash flooding and mudslides occur, especially in parts of Turkey, Syria and northern Iraq.
This Monday, July 16, 2018 photo, shows the Karadeniz Powership Orhan Bey, left, docked as a second floating power station, right, waits off the coast at Jiyeh, south of Beirut, Lebanon. Lebanon received a floating power station from Turkey to ease the rolling blackouts that are a feature of its sticky summers. (AP Photo/Bilal Hussein)
Heavy snow may fall on the mountains well inland, east of the Mediterranean late in the season.
On the southern edge of the storm track, where little or no rain falls, a couple of potent dust storms may sweep from west to east across Saudi Arabia to southern Iran and western Pakistan.
"Just to the north of the storm track, drought conditions will persist and may get worse from the eastern part of Ukraine and the Volga Valley to portions of Kazakhstan," Nicholls said. "This lack of rain could be problematic as there may not be enough moisture for winter grain germination and establishment."
Sufficient rain likely in much of China, Korean Peninsula
Portions of the North China Plain, including the Yangtze Valley, are likely to get off to a drier start than average this autumn.
"A drier start than usual could prove favorable for early harvesting efforts, while rain and snow later in the season could be helpful for winter grain germination and establishment," Nicholls said.
For the season as a whole, adequate rains are anticipated across much of east-central and southeastern China to the Korean Peninsula.
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