AccuWeather's 2020 Asia summer forecast

With just over three weeks to go until summer of 2020 begins, AccuWeather meteorologists released their annual summer forecast for Asia this week. Summer officially begins on June 20, and for some parts of the continent, the season will continue to pose serious tropical dangers.

Drought relief is in store for part of southeastern Asia, even as concerns over dry conditions may worsen over other areas of the continent. Ample precipitation is expected to douse much of India and eastern China as monsoon rains get underway.

Anticipated atmospheric and oceanic conditions may hold the number of tropical systems down to near-average numbers this summer over southern and eastern Asia, but all it takes is for one or two storms to strike a populated area to pose great risk and add to already heightened tensions over the COVID-19 pandemic.

Dan Kottlowski, AccuWeather's top tropical meteorologist, has been analyzing weather trends expected for the season along with Jason Nicholls, AccuWeather's lead international forecaster, and Paul Pastelok, who leads AccuWeather's long-range forecasting team. The team of meteorologists expects the El Nino Southern Oscillation (ENSO) to transition from neutral to La Niña conditions late this summer or this autumn.

The combined experience of these three meteorologists adds up close to 100 years, and other veteran meteorologists with AccuWeather have been actively analyzing the weather patterns across the globe.

"The Pacific Ocean is the largest water body on the planet prevailing water temperature anomalies over the basin can have tremendous influence on the weather," Pastelok said, explaining that a La Niña pattern can have implications on weather patterns around the globe in both short- and long-term scenarios.

This image shows the sea surface temperatures (Celsius) on May 30, 2020. At this time neutral ENSO conditions exist but there may be some early signs of a weak La Niña pattern beginning to develop off the coast of South America as indicated by the plume of cooler water (green). Water temperatures over the northern Indian Ocean are relatively uniform at this time. (NOAA/Climate Prediction Center)

ENSO is a routine fluctuation in sea surface temperatures over the tropical Pacific Ocean. It can take several months to a few years for a complete cycle to occur from warmer-than-average to cooler-than-average water temperatures and vice versa.

With a La Niña forecast to occur later this summer or into this fall, below-average water temperatures are anticipated in the eastern tropical Pacific, and warmer-than-average water temperatures are projected over the western tropical Pacific.

"Water temperature fluctuations over the Indian Ocean also play a major role in Asia's weather," Nicholls said.

Another water temperature cycle, known as the Indian Ocean Dipole (IOD), is also a perennial player in the weather over Asia. The IOD is used to describe the water temperature fluctuations over the eastern and western parts of the Indian Ocean.

Like the Pacific, this water temperature fluctuation maintains a balance with warm water on one side of the basin and cool water on the other. Over the period from this summer to fall, the IOD is forecast to trend negative, which means water temperatures on the eastern side of the basin will become warmer than the western side of the basin.

It is not uncommon during a developing La Niña for a negative IOD to develop as well, and that is the foundation of the tropical forecast for this summer to this autumn in the Pacific and Indian oceans.

"With ENSO conditions expected to trend from neutral to La Niña later this summer to this fall, tropical activity is likely to be below average during the early summer and near average during the late summer to the autumn in the western Pacific," Kottlowski said.

Tropical threats this summer and into the autumn are expected in the western Pacific, including in the Philippines and from southeastern China to Japan.

When La Niña conditions develop, episodes of wind shear, or changing winds with altitude, tend to be more frequent over the western Pacific basin, and the development area tends to be smaller than during El Niño conditions.

"These conditions support a decrease in the number of typhoons and super typhoons," Kottlowski said, adding that studies have also shown that typhoons tend to be shorter-lived when La Niña and increased occurrences of wind shear are prevalent.

The speed at which ocean water temperature changes occur will ultimately determine the numbers of tropical systems and prime development areas of those systems. If the onset of La Niña is delayed, then there could be higher numbers of typhoons and super typhoons and a longer duration of these dangerous cyclones.

Factoring in the anticipated weather patterns as well as examining prior years with similar weather conditions, AccuWeather forecasters expect approximately 29 tropical storms, which is the same figure from last year and slightly above the average of 26 for the West Pacific. Of these, about 17 typhoons are anticipated, which is the same number that developed last year as well as the average for the basin. Typhoons are named when cyclones produce maximum-sustained winds of 74 mph (118 km/h), according to the Joint Typhoon Warning Center.

AccuWeather meteorologists warned that five super typhoons, packing winds of 149 mph (240 km/h) or higher, could develop this season. In 2019, there were four super typhoons, whereas the climatological average is six for the basin.

A surfer walks out of the water as Mount Fuji is visible in the distance after Typhoon Hagibis passed through the area, Sunday, Oct. 13, 2019, in Fujisawa, west of Tokyo. (AP Photo/Jae C. Hong)

"The overall pattern for much of the summer should favor storms taking a curved path toward Japan, but during the late summer and autumn, developing La Niña and the negative Indian Ocean Dipole should cause the main typhoon development area to shift westward over the western Pacific," Nicholls explained.

A westward shift in tropical development could limit the number of direct strikes on Japan, but it would tend to increase the potential for direct impacts in China, Taiwan and perhaps Vietnam during the late summer and autumn.

Surging waves hit against the breakwater and a lighthouse as Typhoon Hagibis approached the port in town of Kiho, Mie prefecture, central Japan Saturday, Oct. 12, 2019. (AP Photo/Toru Hanai)

The Indian Ocean basin has already shown considerable activity this spring. The latest storm during the middle of May, Amphan, became a monster over the Bay of Bengal, before weakening prior to landfall in northern India and Bangladesh on Wednesday, May 20. Despite the storm's weakening, more than 100,000 people were left homeless in Bangladesh and India in the wake of Amphan, according to the AFP. At least 3 million were evacuated ahead of the storm, which was the most powerful tropical system to hit the region this century.

In this Wednesday, May 20, 2020 photo, people crowd a shelter before Cyclone Amphan made landfall, in Shyamnagar, Shatkhira, Bangladesh. (AP Photo/Abu Sufian Jewel)

During the evening of May 18, local time, Amphan peaked as a super cyclonic storm with sustained wind speeds of 137 mph (220 km/h). Amphan was the first super cyclonic storm in the Bay of Bengal since the 1999 Odisha Cyclone. That cyclone in 1999 produced winds up to 160 mph (260 km/h).

People make their way through damaged cables and a tree branch fallen in the middle of a road after Cyclone Amphan hit the region in Kolkata, India, Thursday, May 21, 2020. A powerful cyclone ripped through densely populated coastal India and Bangladesh, blowing off roofs and whipping up waves that swallowed embankments and bridges and left entire villages without access to fresh water, electricity and communications. (AP Photo/Bikas Das)

There is the risk of additional tropical development in the Bay of Bengal and the Arabian Sea during the first part of the summer season.

Cyclonic Storm Nisarga made history when it battered western India with torrential rainfall and damaging winds on Wednesday after becoming the first tropical cyclone in recorded history to strike the city of Mumbai and surrounding districts during the month of June.

Another one of these early-summer storms can enhance rainfall across southern India and Sri Lanka during June, Nicholls warned.

AccuWeather meteorologists expect one or more impacts to the upper west coast of India, Pakistan and the Arabian Peninsula during June.

Any additional tropical development over the Arabian Sea is likely to pose minimal impact to land, but some rain from diminishing tropical systems can reach coastal areas early on in the summer.

As Amphan demonstrated, even during a year in which an average to below-average number of tropical cyclones is forecast, all it takes is for one or two potent storms to strike a populated area to bring great risk to lives and property. "People should not let their guard down," Kottlowski warned.

How strongly La Niña comes on and how negative the Indian Ocean Dipole becomes can affect not only the outcome of the tropical season in the western Pacific but also the amount of rainfall related to the southwest monsoon in India.

For the most part, the southwest monsoon is forecast to begin and advance on schedule, but forecasters expressed some concerns for the season. Most of India can expect near-normal rainfall this year with above-average rainfall forecast for the northwestern part of the country.

One significant concern is for a later-than-average start to monsoon rains in northeastern India, where rainfall was below average last year.

"Any delay in the arrival of the monsoon rains could have some negative impacts on agriculture and water supply in the northeastern part of India," Nicholls said. Conditions are expected to turn around, and rainfall amounts could ramp up as the season progresses.

"Rainfall from Amphan in May will certainly help reduce this risk in part of northeastern India, but areas a bit farther west of the moisture from the storm, such as in western Bihar, including the Patna area, could be at risk for dryness issues," according to AccuWeather Senior Meteorologist Adam Douty.

The developing weather patterns could translate to frequent showers and thunderstorms over Indonesia, Malasia and parts of Southeast Asia this summer, which will be quite the change from extensive drought conditions that took hold of the same regions last summer and autumn.

Agriculture and fishing interests along the Mekong River could benefit from the wet weather setup. Numerous hydroelectric dams and below-normal rainfall caused the flow to dwindle along the major waterway in Southeast Asia in recent years. The Mekong River reached its lowest levels in nearly 100 years in 2019 due to drought and water management politics, according to the National Geographic. Fears of food shortages resulted from the extremely low levels of the river last year.

"A wild card or risk would be if the Indian Ocean Dipole becomes strongly negative," Nicholls said. "If so, this could tilt the balance and lead to dryness concerns later this summer and autumn over Southeast Asia."

Rainfall is likely to be near to above average over much of eastern China to the Korean Peninsula and portions of Japan this summer, although it is possible a drier period may evolve in southeastern China during the middle of the summer.

"Rainfall looks to be adequate for the cotton crop in northwestern China, but opportunities for rain in western China, which is normally dry anyway, may be slim," Nicholls said.

Spells of hot weather are also forecast for eastern parts of China. "We do expect some early-season heat waves in northeastern China, while prolonged heat is not likely in the southeastern part of the country," according to Nicholls.

Visitors wearing face masks to protect against the new coronavirus walk through the Forbidden City in Beijing, Friday, May 1, 2020. The Forbidden City reopened beginning on Friday, China's May Day holiday, to limited visitors after being closed to the public for more than three months during the coronavirus outbreak. (AP Photo/Mark Schiefelbein)

Farther west, much of the Middle East will be seasonably dry with temperatures predicted to be a bit higher than average.

"It appears that moisture from the western extent of the southwest monsoon will fuel a few rounds of thunderstorms over southwestern Saudi Arabia and western Yemen during the middle to latter part of the summer," Nicholls said.

There can even be spotty thunderstorms over the higher elevations of the United Arab Emirates and northern Oman on occasion. Spotty storms are also foreseen over the mountains of Afghanistan and Pakistan later in the summer.

"We are expecting substantial rainfall in southwestern Oman and southeastern Yemen related to a local monsoon called the al-khareef," Nicholls said.

Tourists ride electric boats in a seasonal lake in Wadi al-Dirbat, Oman, on Sunday, July 31, 2017. The otherwise extremely arid region blooms during the monsoon, known as "al-khareef" in Arabic, drenches the southern Arabian peninsula with rain and creates stormy seas. (AP Photo/Sam McNeil)

This wet season typically spans the months of July, August and September as a narrow ribbon of moisture is funneled northwestward from the Indian Ocean.

Farther northwest, ongoing drier and warmer conditions in the Ukraine and southwestern Russia are likely to continue to evolve.

"There is the potential for a significant long-term drought over the Volga Valley, which can result in reduced crop yields, especially with corn," Nicholls said.

Building dryness and warmth are also likely to lead to pockets of reduced crop yields over Kazakhstan later this summer and autumn.