Hurricane Imogen intensified to a Category 4 storm overnight and is now forecast to make landfall somewhere between the Carolinas and Nova Scotia within 36 hours. Evacuation orders are in effect for coastal counties in three US states, and Environment Canada has placed all of Atlantic Canada under a tropical cyclone watch.

Forecast models still disagree sharply on the track. The American and European ensembles are roughly 400 kilometres apart on where the eye comes ashore, and officials on both sides of the border say the landfall point could shift again before Tuesday morning.

Transport operators are already feeling it: ferries across the Gulf are suspended, and two major airlines have begun pre-emptively cancelling Tuesday departures from Halifax, Boston and New York.