Within favorable conditions aloft , the storm intensified Cause_change_of_strength into a tropical storm as it tracked Self_motion northward .

A secondary low developed Coming_to_be over South Carolina on the next day , supported Supporting by the merger Cause_to_amalgamate of two troughs aloft .

The combination of the absorption of a second low-pressure area to its southeast , a stronger than normal sea surface temperature differential along its path , and the presence Presence of a strong jet stream aloft led to Causation a rapid strengthening Cause_change_of_strength of the storm Catastrophe , with its central pressure falling Motion_directional to an estimated on 10 January .