 After becoming an extratropical low , the remnants of Ivan turned to the southeast and emerged into the Atlantic Ocean , due to the building of an upper @-@ level ridge to its east . As an extratropical cyclone , Ivan remained identifiable in both surface and upper @-@ level data , and the system turned south and southwestward over the subsequent days . By September 20 , the system was located off the east coast of Florida , producing scattered thunderstorms ; unfavorable wind shear prevented tropical redevelopment , though forecasters indicated the possibility for more favorable conditions a few days later . On September 21 the low crossed southern Florida and emerged into the Gulf of Mexico , and as it moved across the warm waters of the region the low began to re @-@ acquire tropical characteristics ; the low @-@ level circulation became increasingly better defined , and convection redeveloped over the center . Based on reports from Hurricane Hunters , it is estimated the low redeveloped into Tropical Depression Ivan late on September 22 while located about 175 miles ( 280 km ) south @-@ southeast of the mouth of the Mississippi River . 
