"he [Jonah] cried and said..."
Considering whole the story, Jonah does not seem to be a man who tries to do everything God says. His anger against Niniveh could play a role in how he presented the message. Or maybe he presented just a part of it and left out the part about possible escape.
9 Who can tell if God will turn and repent, and turn away from his fierce anger, that we perish not?
10 And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not.
God changed His mind concerning overthrowing them, instead He showed them mercy. God had every intention of overthrowing Nineveh in forty days.