 Early on November 17 , an extratropical low developed along a stationary front over the central Atlantic . It moved northward and became co @-@ located with an upper @-@ level low . After the fronts dissipated , deep convection began to initiate near the center . As a result , Subtropical Storm Melissa developed at 12 : 00 UTC on November 18 , about 720 mi ( 1 @,@ 160 km ) east @-@ southeast of Bermuda . Melissa moved generally northward and strengthened slightly on November 19 , but weakened later that day after convection diminished . Early on November 20 , convection increased again , and after the storm acquired a warm core , it was reclassified as a tropical storm . 
