These regions could receive localised totals of up to 15cm of rain, according to the NHC.
The agency’s deputy director, Jamie Rhome, warned Americans not to assume the hurricane won’t impact them simply because its track keeps it offshore.
“Nothing could be further from the truth for portions of the Mid-Atlantic, especially the Outer Banks of North Carolina,” he said. On Wednesday and Thursday, waves of up to 6m, coastal flooding and storm surge “could overwash dunes and flood homes, flood roads and make some communities impassable”, he said.
Evacuations have been ordered for two North Carolina islands, Ocracoke and Hatteras.
From Tuesday, much of the East Coast will face a high risk of life-threatening surf and rip currents, which occur when channels of water surge away from the shore.
In Puerto Rico, a US territory of more than three million people, weekend flooding swamped homes and roads in the island’s east, and widespread power outages left residents in the dark, though nearly all service has since been restored.
Climate link
“Erin is one of the fastest, most intensifying storms in the modern record,” Daniel Gilford, a climate scientist at the nonprofit Climate Central, told AFP.
“We see that it has intensified over these warm surface temperatures – and this makes a lot of sense, because we know that hurricanes act like heat engines taking up energy from the ocean surface, converting that energy into winds.”
According to Climate Central, Erin travelled over waters whose extreme warmth was made up to 100 times more likely through climate change.
The Atlantic hurricane season, which runs from June 1 to November 30, has now entered its historical peak.
Despite a relatively quiet start with just four named storms so far, the National Oceanic and Atmospheric Administration (NOAA) continues to forecast an “above-normal” season.
A typical season produces 14 named storms, of which seven become hurricanes and three strengthen into major hurricanes.
This year, tropical activity is expected to be elevated by a combination of warmer-than-average sea-surface temperatures in the tropical Atlantic and Caribbean, with an active West African monsoon, NOAA said.
Scientists broadly agree that climate change is supercharging tropical cyclones: warmer oceans fuel stronger winds, a warmer atmosphere intensifies rainfall, and higher sea levels magnify storm surge.
Climate change may also be making hurricanes more frequent.
– Agence France-Presse