 Marked structural improvements took place on October 17 and the NHC assessed a high probability of the system becoming a tropical cyclone within 48 hours . That evening , corroborating data from ships , satellite imagery , and scatterometer estimates indicated the formation of a tropical depression by 12 : 00 UTC . With the cyclone located over warm waters of 86 ° F ( 30 ° C ) and within a very moist region with low wind shear , intensification was a certainty as the depression approached Mexico . Uncertainties existed as to how fast the system would move . Some forecast models depicting the system as stalling just offshore for several days , though forecasters indicated that a steady northward movement would lead to dissipation within 48 hours . 
