 On August 26 , the National Hurricane Center ( NHC ) began monitoring a tropical wave between the western coast of Africa and the Cape Verde Islands . Later that day , a low @-@ level circulation center formed beneath the wave and began strengthening . Convective activity associated with the low became increasingly organized , and at around 1200 UTC on August 27 , the NHC classified the system as Tropical Depression Thirteen ; at the time , it was located approximately 255 miles ( 410 kilometres ) south @-@ southeast of Praia , Cape Verde . Operationally , the NHC did not begin to issue advisories on the depression until 2100 UTC on August 28 . Tracking nearly due west in response to an anticyclone to the north and an area of moderate wind shear , the depression was forecast to slowly strengthen over the next several days . Early on August 29 , satellite intensity estimates of maximum sustained winds within the depression reached 40 mph ( 65 km / h ) , indicating that it had intensified into a tropical storm . At this time , the NHC assigned the name Luis to the system . Gradual strengthening took place throughout August 29 as Luis tracked towards the west @-@ northwest . Increased wind shear displaced convection from the center of circulation , preventing further intensification . 
