Riding a high tide of strong exports and better-than-expected imports, and with a wave a Christmas imports on the horizon, port executives expect to hit another high-water mark for 1995.

Containerized imports increased 8 percent in May and exports surged 16 percent, according to PIERS, the Port Import/Export Reporting Service of The Journal of Commerce. With Christmas cargo starting to appear, port executives are talking about a double-digit increase in container volume for 1995."Growth has been steady all year, and I think it's going to continue," said L. Duane Grantham, director of marketing at the Port of Charleston, S.C. Container volume in Charleston increased 23 percent through May, and The port saw a 27 percent increase in May's performance compared to May 1994.

Charleston's performance was typical of major U.S. containerports in May. Imports increased in Charleston, even though the spring is normally a slow season. Exports remained especially strong as the weak dollar made U.S. goods more competitive overseas.

The U.S. container trade heated up to 11 percent growth in 1994 after six years of growth in the more traditional 6 percent range. Economists said unusually strong exports and the failure of the weak dollar to stymie imports created a one-time surge in trade that would cool down in 1995.

So far, the economists have been wrong. Container volume increased 14 percent in the first five months of the year, far more than the single-digit growth that was anticipated. Six of the top seven U.S. containerports recorded double-digit growth.

Dene Hurley, senior trade economist for PIERS, said, "Exports are doing pretty well in general. In South America, Brazil is opening its markets and lowering tariffs, and Venezuela's economy is recovering a little bit as banks are becoming stabilized."

As for exports to Asia, "China will be the fastest-growing market, primarily because they are taking a lot of cotton and consumer goods such as meats, fruits, and vegetables. There will be export growth because China and Japan are opening their markets to U.S. farm products," Ms. Hurley said.

"We said in 'Trade Horizons' that imports were not doing as well as exports for the first quarter," she said. "In Asia, China is the big news. On the import side, China was a strong traffic lane for first-quarter 1995. Japan, Korea and Taiwan were flat because they were pricing themselves out of the U.S. market. In Southeast Asia, Malaysia and the Philippines are doing well."

Long Beach and Los Angeles continue to solidify their ranking as the nation's top containerports. Container volume in Long Beach increased 18 percent through May. Los Angeles was up 15 percent.

Don Wylie, director of trade and maritime services in Long Beach, said import growth slowed somewhat in the first quarter, as anticipated. But now that Christmas shipments are beginning to move, he said, "we're expecting a very strong second half of the year."

Long Beach and Los Angeles are anticipating another surge in cargo volume in 1996, as trans-Pacific carriers bring large new containerships into their fleets. These vessels, with a capacity of about 5,000 20-foot equivalent units, will be 25 percent larger than the current generation of ships.

Carriers will introduce approximately 40 containerships in the 4,750-to- 5,250-TEU range over the next two years. Many of the vessels will be operated in the trans-Pacific services to Southern California.

Carriers normally use their biggest containerships in their Pacific Southwest services, because of the large local population and extensive intermodal service to the eastern half of the country.

Bill Grindrod, assistant director of marketing in Los Angeles, said there is also a good economic reason to funnel more cargo through major load centers. After carriers reach a certain volume threshold, their port fees drop off considerably. "It really makes the load-center concept worthwhile," he said.

Trade with Asia accounts for more than 50 percent of U.S. commerce, and that is why West Coast ports dominate the port rankings. However, Latin America is the fastest-growing region for U.S. trade, and Eastern ports are benefiting the most from this trend.

"Latin America accounts for 75 percent to 80 percent of our trade," said Carlos Buqueras, director of cargo marketing at Port Everglades. That South Florida port has been on a tear this year, with container volume up more than 50 percent. Mr. Buqueras said Brazil has replaced Japan as Florida's top trading partner.

In addition to benefiting from the growing trade with Latin America, Port Everglades has attracted several new services, including two that formerly called at Miami. "We added capacity (terminal space) and we marketed the hell out of it," Mr. Buqueras said.

Most of the nation's top containerports are experiencing double-digit container growth in the first five months of the year. Those that aren't can often point to extraordinary circumstances.

Baltimore, for example, lost a Maersk Inc. service in January because of a scheduling conflict. Maersk, the third-largest carrier in the U.S. trades, returned its South American service to Baltimore in June. With the return of Maersk, and a new service by Chilean Line, Baltimore will have a strong second half of 1995, said port spokesman Jim Gring.

Tacoma, Wash., in May rejoined other major West Coast ports in double-digit growth. Last spring the port was hit hard when Sea-Land Service Inc. diverted its ships to Canada because of a Teamsters strike at its Tacoma terminal.

Container volume jumped 16 percent in May. Doug Ljungren, Tacoma's business-planning manager, said exports have been so strong that some vessels are being overbooked. "There's been just a little weakness in imports, but on exports, some lines are still rolling cargo," he said.