East Coast ports benefit from West Coast discord

The NYK Joanna container ship sits docked at the Dante B. Fascell Port of Miami-Dade County in Miami, Florida.
Mark Elias | Bloomberg | Getty Images
The NYK Joanna container ship sits docked at the Dante B. Fascell Port of Miami-Dade County in Miami, Florida.

The labor strikes at the West Coast Ports earlier this year may have wreaked havoc on shippers, transportation companies and consumers, but there has been one winner: East Coast rivals.

The amount of so-called containerized imports coming into Atlantic ports in February came very close to matching that of the historically busier West Coast, according to the Journal of Commerce, as activity on the two U.S. coasts "almost reached parity."

The Journal of Commerce report is based on data collected by the Port Import/Export Reporting Service (PIERS), its sister company under the IHS Maritime & Trade umbrella.

Read MoreCalifornia ports congestion 'worst-ever on record'

"East Coast imports consistently outperformed West Coast imports from November through February in terms of year-over-year growth. Gulf Coast ports also experienced growth in imports, but the Gulf's performance comes on a much lower cargo base, with a market share of about 6 percent of total U.S. containerized imports," wrote Bill Mangelluzzo, a senior editor at JOC.

In February, East Coast ports handled 658,768 20-foot equivalent units (TEU), or just 3 percent less than the 673,318 TEUs handled by West Coast piers. That's a dramatic difference from July 2014, the month in which a coast-wide labor contract between the International Longshore and Warehouse Union (ILWU) and the Pacific Maritime Association (PMA) expired—when the West Coast ports handled 33 percent more containers.

The subsequent nine-month labor dispute culminated in fierce gridlock at West Coast ports, with the country's two busiest container ports, in Los Angeles and Long Beach, racking up massive backlogs that are still being worked through.

Read MoreCustomers to ports and workers: Get it done!

The ILWU and PMA reached a tentative deal for a new five-year agreement in late February that should be finalized in May. Meantime, even as operations at the ports have resumed, the backlogs have weighed on transportation companies' reported volumes and analysts have said the backlogs could still take weeks, even months, to subside.

The scenario has caused many shippers to bypass the West Coast, the fastest and most economical delivery point for goods coming into the country from Asia via ship, and reroute shipments to ports in other parts of North America, from Canada to Mexico to the U.S. Gulf.

Much of that diverted cargo has made its way to hubs along the East Coast, from Miami, Florida, to Savannah, Georgia. To Baltimore, Maryland, to the country's third-largest container port in Newark, New Jersey. The JOC/PIERS containerized import numbers for February reflect this ongoing dynamic.

Other data have pointed to the same trend. According to the Global Port Tracker, which is put out by the National Retail Federation and Hackett Associates, West Coast retail container ports handled 55 percent of import cargo in January, while East Coast ports handled 45 percent; that breakdown during the same period last year was 64 percent versus 36 percent, respectively.

Read MoreWest Coast ports situation hurts retailers the most

"Importers and exporters are reviewing their supply chain plans for the future, and not necessarily in favor of the West Coast," Hackett Associates founder Ben Hackett said in a March Global Report Tracker report.

Still, analysts expect these new traffic flows to begin reversing as congestion eases along the West Coast, due largely to the fact that for many shippers, it's too expensive to move high-value imported goods anywhere but the West Coast. For example, transit time is an essential part of the total cost of transportation for seasonal products. Delivery from Asia to the East Coast via ship can take one to two weeks longer than delivery along the West Coast.

Those lengthier hauls (not to mention adoption of other faster types of travel such as air freight) have been weighing on a number of companies' earnings, particularly retailers since late last year.

Read MoreWest Coast ports: Retail's $7 billion problem

For that reason many expect the West Coast to begin regaining market share in the coming months. NRF forecasts that West Coast volumes will total 12.05 million TEUs this year, East Coast ports 7.6 million TEUs.

Still, the question remains: How much will ultimately return to its prior port of entry? It's unlikely the East Coast will cede all of its newfound business, in much the same way it permanently picked up more cargo—albeit in a small fraction—in the years after the West Coast port-labor lockout in 2002.

Then there's the Panama Canal, which has been undergoing a multibillion-dollar expansion. That project could prove an attractive option for shippers whose goods ultimately need to be delivered in the eastern part of the U.S. The canal's expansion is expected to be completed in early 2016.