What happens in the spring to monarchs that overwinter on the coasts?

The red triangles on the map below are places where monarchs were sighted during the winter (January or February). If they survived the winter, do those monarchs migrate northward, travel in different directions, or just stay where they are? We do know that monarchs who overwintered on the California coast move inland and northward. Do those on the Gulf and Atlantic Coasts do the same? How could we find out?