 A squall line which moved offshore New York and southern New England formed a mesoscale convective vortex , which fired new thunderstorm activity each day as it moved within the westerlies across the northern Atlantic . Once it reached mid @-@ ocean , an increasingly northerly steering flow dropped the system down into the subtropics to the east of Bermuda , and it maintained decent organization . By 2100 UTC on July 24 , the National Hurricane Center began classifying the system as Tropical Depression Two . In the first advisory on the depression , it was noted that the previous tropical depression was erroneously classified as Tropical Depression Two . 
