Hurricane Sandy moved near southeast Florida Friday and may mix with an icy storm as it chugs up the east coast, making what forecasters dubbed \"Frankenstorm.\" Sandy, weakened to a Category 1 storm after whipping through the Bahamas, moved north-northwest at 13 mph toward the Florida Keys. The storm system began whipping up gale-force winds in southeast and east-central Florida early Friday. Some school districts canceled classes. Officials warned residents of dangerous coastal rip currents. A tropical storm warning was in effect for the state\'s east coast from Ocean Reef in the upper Keys to Flagler Beach, 70 miles southeast of Jacksonville, the National Hurricane Center in Miami said. A tropical storm watch was in effect for points north. A warning means tropical storm-force winds between 37 mph and 74 mph are occurring or are expected within 24 hours. A watch means those winds could hit within 36 hours. Waves near shore were rising Friday to a forecast 12 feet to 18 feet, with offshore waves 18 feet to 22 feet. Sandy -- which whipped through the central Bahamas with violent winds and torrential rains Thursday -- killed at least 21 people across the Caribbean. State media in Cuba said at least 11 people died as Sandy, then a Category 2 hurricane, brought down buildings and trees in the eastern provinces of Santiago and Guantanamo. Haiti reported at least nine deaths and Jamaica reported at least one. Sandy is forecast to move north from Florida along the Atlantic Seaboard and could combine, in an unusual confluence of weather patterns, with an early winter storm moving eastward from the Great Lakes and a blast of arctic air from the north, forecasters said. The result could be rain, snow and fierce winds thrashing several Northeastern states starting Tuesday through Halloween Wednesday -- giving rise to the \"Frankenstorm\" nickname. Amplifying the weather consequences will be a full moon Monday. New York, New Jersey and Connecticut -- socked by Tropical Storm Irene last year -- could be hardest hit, forecasters said. Meteorologists said chances were increasingly slim the storm would veer into the Atlantic Ocean and leave the east coast alone, forecasters told The Wall Street Journal. But it wasn\'t clear how big and bad Sandy would be, forecasters said. When it makes Northeast landfall Tuesday, it may no longer be a hurricane. Still, New York Gov. Andrew Cuomo\'s office warned in a statement of \"heavy rain, high winds, flooding, tornadoes, coastal surges and widespread power outages\" as early as Tuesday. New Jersey officials said they were monitoring flood-prone areas for possible evacuations. Connecticut power companies braced for a test of a revamped storm-preparation system, the Journal said.