A picturesque vacation for hundreds of Chinese tourists turned into a nightmare on June 1, when high winds associated with an intense thunderstorm capsized the Oriental Star cruise ship in 50-foot-deep water
on the Yangtze River in Hubei Province, southwest of Wuhan, at around 9:30 pm
local time. As of Tuesday afternoon, only 14 people had been rescued from about 450 reportedly on board
, most of them retirees on a multiday scenic cruise from Nanjing to Chongqing. The disaster appears set to become China’s deadliest ship-related accident in almost 70 years
. It’s unclear whether the cruise ship was sunk by a tornado or by a microburst, but in either event, the death toll could end up among the largest on record associated with a single thunderstorm. A 2011 post by WU weather historian Christopher Burt
showed less than 10 tornadoes worldwide that inflicted a greater toll than the potential 400-plus deaths abroad the Oriental Star. As we’ll see below, the event also brings to mind a similar U.S. tragedy almost 40 years ago.Figure 1.
Rescuers search for survivors from the capsized ship Dongfangzhixing (Eastern Star) in the Yangtze River on June 2, 2015, in Jingzhou, China. Image credit: ChinaFotoPress/Getty Images.What caused the high winds?
Press coverage has led to some understandable confusion over exactly what caused the disaster. China’s Xinhua news agency reported
that the China Meteorological Agency (CMA) detected winds “stronger than 12 scale,” apparently a reference to the Beaufort scale, where 12 corresponds to winds exceeding hurricane force (74 mph). The Guardian cites local media
as reporting winds of 80 mph at the time of the accident. Several news reports called the event a cyclone, while others dubbed it a tornado. Given that tornadoes have cyclonically oriented winds, they are sometimes referred to as cyclones in news reports outside the United States. Moreover, according to the New York Times
, “In Chinese, the term for tornado, longjuanfeng, is used more loosely than Americans use its English equivalent.” Figure 2.
An infrared satellite image taken at around midnight local time on Monday night, June 1, several hours after the Eastern Star ship was hit by high winds. Image credit: weather.com
. An infrared loop
from Japan’s new Himawari-8 satellite illustrates the same storm complex, with an blue “X” placed at the approximate location of the capsizing. Image credit: Japan Meteorological Agency, courtesy Dan Lindsey, Cooperative Institute for Research in the Atmosphere
Satellite images from the region around the disaster show a large cluster of strong thunderstorms developing on Monday night local time (see Figure 2). Eastern Asia has some of the same thunderstorm-favorable features as the U.S. Great Plains, including mountains and dry air to the west and access to very warm, humid air toward the south and east. However, little has been published in the global science literature on the frequency of tornadoes across China. “Thunderstorms have certainly been plentiful across eastern and southern China over the past few days," said Jon Erdman
in a weather.com article
. "It's certainly possible one of those thunderstorms may have spawned a very unfortunately-timed tornado. . . .Also, strong straight-line, non-tornadic winds—common in clusters of thunderstorms like those seen in eastern China late Monday—may have played a role in the capsizing."
Harold Brooks (NOAA National Severe Storms Laboratory), an expert on international tornado climatology, inspected upper-air soundings collected across the central Yangtze region on Monday evening. Brooks told me the soundings were supportive of tornadic supercells, with ample instability (CAPE
values of 1000 to 3000 J/kg) and adequate storm-relative helicity
(a measure of potential updraft rotation). However, such conditions can also lead to high-precipitation storms that produce strong downburst winds but no tornado. “Given the environment, I wouldn't be surprised if it was a tornado or, at least, a strong rear-flank downdraft
associated with a supercell,” said Brooks.
Monday’s storms developed along a seasonal feature called the Mei-yu front
, a band of convergent winds associated with the northward push of the Asian monsoon in China and Japan. Each spring, the cold, parched winter climate of China transitions to a muggy summer regime that includes frequent rounds of torrential rain. Beijing’s average precipitation in July (7.3”) is far greater than its average in January (0.1”). The Asian monsoon is driven by southwesterly upper winds toward the northeast, so it reaches a higher latitude sooner than the Indian monsoon. This explains why heavy rains can strike central China (latitude 30°N) while parts of India as far south as 10°N have yet to see the monsoon. The Mei-yu front can stall out for weeks during May and June in the general vicinity of the Yangtze, leading to days of heavy thunderstorms along and near it. BBC reported
that the Mei-yu rains this season have been the heaviest in 40 years across parts of south China.
Figure 3. A bridge damaged by flood water in Leishan county of southwest China’s Guizhou province on May 27, 2015. Parts of China have been hit by the heaviest spring rains in 40 years. Image credit: AFP/Getty Images.The Whippoorwill disaster of 1978
Though far less deadly than its present-day counterpart in China, the capsizing of a pleasure boat called the Whippoorwill
led to one of the ten worst tornado tolls
in the history of Kansas. On June 17, 1978, the Whippoorwill carried 58 passengers on an evening cruise on the 4,000-acre Pomona Lake
, about 30 miles south of Topeka. A small tornado, only about 150 yards wide but with multiple vortices, developed near the lake around 7:00 pm, according to a summary
from the National Weather Service office in Topeka. Damage was minimal, but the suddenness of the tornado’s development and its unfortunate path led to the capsizing of the showboat. One victim recalled
: “One minute we were serving salads, the next I was under water.” There were 16 fatalities. “Nationwide media coverage was focused on Kansas and this tornado for many days after the tragic event,” notes the NWS/Topeka. “People who boarded the Whippoorwill for an evening of fun and entertainment, likely never imagined what a historical catastrophe they were in for.” As part of the 50th anniversary of the creation of Pomona Lake, a memorial service
was held last June 17 for the victims of the Whippoorwill disaster.
My thanks go to Harold Brooks (NOAA/NSSL), Roger Edwards (NOAA Storm Prediction Center), and WU weather historian Christopher Burt for background used in this article.