Retail sales jumped 1.1 percent in November, only slightly offsetting a steep 4.2 percent decline in October but reviving hopes that consumers will spend enough to produce a "green" Christmas for merchants.

Economists said they were surprised by the strength of sales, although many analysts said they were still cautious about suggesting a strong rebound in spending. The caution is prompted by the fact that consumer debt levels are historically high when savings are at record lows -- a situation that is eventually expected to put the brakes on consumer expenditures. Consumer spending contributes about two-thirds to gross national product -- the nation's output of goods and services.

However, spending last month appeared brisk, as automobile sales rose after an August slump, and department store sales increased 1.3 percent. Total retail sales increased to a seasonally adjusted $115.85 billion from $114.55 billion in October.

White House spokesman Larry Speakes said that the increase "should portend a strong 1985 holiday sales season." He also said that the administration expects the gross national product to grow at a 5 percent rate in the second half of this year and at 4 percent next year.

Many economists said they expect a more sluggish fourth quarter than the administration forecast and overall growth in the 2.5 percent-to-3 percent range for 1986.

"It's a surprisingly good result," Roger Brinner of Data Resources Inc. said of the retail sales figures for November. "The auto sales bounceback reflects the domestic producers' determination to keep sales alive with new financing incentives and aggressive dealer bargains. The non-auto sector has basically been pretty strong all year. Consumers still think it's a pretty good time to buy." The retail sales report "bodes well for Christmas sales," Brinner said.

Charles Lieberman, a senior economist for Shearson Lehman Bros., said that the retail sales figures were "surprisingly good," particularly sales at department stores. However, he said, "I still think it's going to be a moderate Christmas."

Automobile sales rose 0.9 percent in November, following a 17.2 percent drop in October, the Commerce Department reported. Excluding autos, total retail sales were up 1.2 percent, the sharpest rise since a 2 percent increase in April.

Department store sales rose 1.3 percent, compared with 0.3 percent in October. Sales at furniture stores dropped 0.4 percent, and those at hardware stores fell 0.5 percent. Grocery store purchases rose 1.4 percent and restaurant sales increased 2.3 percent last month.