Supply chain disruptions in Shanghai continue amid ongoing lockdowns in the major shipping and air cargo hub.

Windward's Maritime AI platform showed that the number of containerships waiting outside China's ports has almost doubled since February.

China currently pursues a Zero-Covid policy with measures including putting some of its cities on various types of lockdown to curb coronavirus outbreaks. Most recently, it placed Shanghai on lockdown from March 28 — while it also implemented a lockdown in Shenzhen, another important port city, earlier in March. 

Windward said Shanghai became the largest city to go into lockdown since the beginning of the COVID-19 outbreak and the city's port is the largest in the world in terms of container throughput as such, the effects on global shipping were "quickly felt."

"As data pulled from Windward's Maritime AI platform clearly shows, lockdowns in China are heavily impacting the congestion outside the country's ports, as the number of container vessels waiting outside of Chinese ports today is 195% higher than it was in February," the maritime AI company said.

"The trend is clear – in the April and March snapshots, there were 506 and 470 vessels, respectively, stuck outside of Chinese ports. In February, that number was only 260. In essence, lockdowns in China have nearly doubled the congestion outside the country’s ports," it added.

According to Windward, between April 12-and 13, there were 1,826 container vessels were waiting outside of ports worldwide — or 20% of all container vessels globally.

"Equally interesting is the fact that the 506 vessels that were stuck outside of China's port represent 27.7% of all vessels that were waiting outside of ports around the world. For comparison, in February, they represented 14.8%," the maritime AI company further said.

Companies in Shanghai are restarting operations through a "closed-loop system" after submitting plans to authorities on how to halt the spread of the coronavirus.

Nonetheless, container yards have become highly congested with trucking severely impacted by strict measures in the city including requirements for a negative test in the last 48 hours. Warehouses have also been closed due to the lockdown.

Meanwhile, the major air cargo and shipping hub continues to tally over 20,000 Covid cases reported daily.