NEW YORK (CNN/Money) - Retailers are expecting to ring up their best holiday sales gains in four years, the National Retail Federation said Tuesday.

The NRF, which represents the retail industry, said sales for the crucial November and December shopping period are expected to grow 5.7 percent from last year to about $217 billion, the biggest increase since an 8.2 percent jump in holiday sales in 1999.

"After several strong months of retail sales growth, it seems clear that the economy is picking up momentum just in time for the holidays," NRF chief economist Rosalind Wells said at a press conference at the flagship Toys R Us store in New York City.

"Retail sales gains for the 2003 holiday season will be far better than the meager increases retailers experienced a year ago," she said.

Holiday sales grew just 2.2 percent to $205.6 billion last year, the worst Christmas for retailers in a decade as consumers shied away from spending freely amid a sluggish economy and a weak job market. Retailers can post half or more of their annual sales and profits during the eight-week holiday selling period.

Low interest rates and inflation, as well as the tax cuts, put more money into consumers' wallets and boosted spending this year, economists and analysts say.

Wells, however, noted the weak job market, higher energy prices and geopolitical concerns are concerns for retailers going forward.

But a more immediate threat to retail sales is Hurricane Isabel, which is fast approaching the U.S. East Coast, according to Merrill Lynch retail analyst Daniel Barry.

"We believe that Hurricane Isabel could negatively impact September sales by approximately 0.5 to 1.0 percent. Retail stock prices have historically declined during hurricanes 54 percent of the time but usually recover quickly," Barry wrote in a research report Tuesday.

"Despite the hurricane, we believe that the back-to-school season could be one of the best in years with particularly strong sales in the month of September, especially later in the month when weather is expected to be especially favorable," said Barry.

Kurt Barnard, an independent retail consultant, said the NRF's holiday forecast looked a bit optimistic.

"The 5.7 percent projection is not too much out of line, but it is at the higher end of projections," said Barnard. He expects holiday sales to grow a more modest 3.5 to 4 percent.

Michael Niemira, senior economist with Bank of Tokyo-Mitsubishi, said 5.7 percent growth is "doable. The momentum is in place and consumers continue to spend."

According to Niemira, sales at stores open at least a year -- a key measure known as same-store sales -- are expected to grow 4.5 percent over last year.

But retailers are cautious.

"We expect sales up in the second half, but we're planning more conservatively and we'll see what the outcome is," Richard Markee, vice chairman and president of U.S. Toys R Us stores, said at the press conference.