Simplify the following text for a Grade 11 native English-speaking person.
Original: However , when a northward motion became apparent , the government of Mexico issued a tropical storm warning from Manzanillo , Colima , to Cabo Corrientes and for the Islas Marias .
Simplified: However , when they later found out that the storm would affect land , the government of Mexico issued a tropical storm warning from Manzanillo , Colima , to Cabo Corrientes .