 In mid @-@ October , a strong upper @-@ level trough and a tropical wave interacted while located in the central Atlantic . The system moved slowly westward and convection began increasing . By October 19 , the system became stationary and developed a surface circulation . Later that day , Tropical Depression Eighteen developed about 690 miles ( 1 @,@ 110 km ) southeast of Bermuda . Initially , the depression lacked a well @-@ defined center , though a broad circulation was evident . The depression tracked slowly northward and then northeastward around a subtropical ridge and ahead of a cold front . As wind shear decreased , convective activity became better organized on October 20 . By 1200 UTC on that day , the depression was upgraded to Tropical Storm Nadine . Although it was strengthening , QuikSCAT suggested that the low @-@ level circulation was falling apart , as it appeared to be merging with the cold front . 
