▁Atlantic ▁h urr icane ▁re analysis ▁project , ▁the ▁ 1 9 1 5   New ▁Orleans ▁h urr icane ▁began ▁as ▁a ▁weak ▁tropical ▁storm ▁moving ▁across ▁the ▁southern ▁Wind ward ▁Islands ▁on ▁September   2 1 , ▁ 1 9 1 5 . ▁Its ▁tropical ▁cy c log en esis ▁was ▁determined ▁via ▁analysis ▁of ▁atmos pher ic ▁observations ▁from ▁the ▁surrounding ▁islands , ▁though ▁sh ipping ▁in ▁the ▁region ▁would ▁confirm ▁the ▁storm ' s ▁existence ▁the ▁following ▁day . ▁Track ing ▁slowly ▁towards ▁the ▁west , ▁the ▁nas cent ▁tropical ▁cy clone ▁gradually ▁strength ened , ▁reaching ▁h urr icane ▁intensity ▁by ▁ 0 0 : 0 0   UTC ▁on ▁September   2 3 . ▁This ▁steady ▁phase ▁of ▁intens ification ▁would ▁continue ▁unh inder ed ▁as ▁the ▁h urr icane ▁progress ed ▁across ▁the ▁Car ib bean ▁Sea , ▁allowing ▁the ▁storm ▁to ▁reach ▁major ▁h urr icane ▁strength ▁on ▁September   2 4 . ▁At ▁ 1 2 : 0 0   UTC ▁the ▁next ▁day , ▁the ▁cy clone ' s ▁maximum ▁sust ained ▁wind s ▁cr ested ▁at ▁ 1 4 5   m ph ▁( 2 3 0   km / h ), ▁making ▁it ▁a ▁powerful ▁Category   4 ▁h urr icane ▁if ▁r ated ▁using ▁the ▁modern - day ▁S aff ir – Sim pson ▁h urr icane ▁wind ▁scale ; ▁the ▁storm ▁would ▁maintain ▁wind s ▁of ▁this ▁scale ▁for ▁over ▁three ▁days . ▁One ▁ship ▁observation , ▁estimated ▁to