MIAMI - Tropical Storm Tammy formed just off Florida's east coast Wednesday and was expected to bring heavy rain to northern Florida and parts of Georgia and the Carolinas later in the day.

Tammy, with winds of 40 mph, was centered about 20 miles east of Cape Canaveral at 7:30 a.m. and was moving to the north-northwest at 16 mph. It is expected to continue moving in that direction while gradually slowing its forward motion.

A tropical storm warning has been issued from Cocoa Beach north to Santee River just south of Georgetown, S.C., meaning tropical storm conditions are expected in those areas within the next 24 hours.

Robbie Berg, a meterologist at the National Hurricane Center in Miami, said because Tammy will spend so little time over water, it is unlikely that it will reach hurricane strength of 74 mph.

He said it is hard to forecast where Tammy will make landfall because it is moving parallel to the coast "and one slight variation in its track could bring it onshore."

Rainfall is expected to be 3 to 5 inches in most areas with some isolated spots getting from 8 to 10 inches. Tornadoes are also possible.

Tammy is the 19th named storm of the Atlantic hurricane season, which began June 1 and ends Nov. 30.

This is tied for the second-busiest season since record-keeping started in 1851; 19 storms also formed in 1995 and 1887. The record for tropical storms and hurricanes in one year is 21, set in 1933.