Grapevine: Jan. 9, 1989

THOSE SOUTHERN NIGHTS. Vietnamese officials may not admit it, but Ho Chi Minh City (formerly Saigon) has become the country's unofficial winter capital. Virtually the entire 14-man Politburo, including 75-year-old General Secretary Nguyen Van Linh, prefers the balmy climate of the former imperialist bastion to the damp cold of Hanoi, the capital, which is 700 miles to the north. But the old warriors are careful to maintain appearances: when they have to receive foreign ministers and issue government announcements, Politburo members return -- briefly -- to Hanoi.