The National Hurricane Centre said that its planes had found Jose is now a Category 4 hurricane, with speeds of up to 150 miles per hour. Hurricane categories go up to 5, but it is possible that Jose will be further upgraded before it makes landfall.
The new hurricane's path passes over many of the islands that took the biggest beating from Irma, including Barbuda and St Martin.
Countries including France and the UK have sent resources and people to the islands in an attempt to get them resilient before Saturday, when the huge new storm is set to arrive.
Two Dutch navy ships were in St. Martin with vital supplies. And two Dutch military aircraft were being sent the island of Curacao and on to St. Martin to deliver food and water intended to last the population of 40,000 five days. The aircraft were carrying 100 extra troops to deliver aid, repair infrastructure and restore order.
Britain was sending hundreds of troops and the Royal Navy flagship HMS Ocean to Anguilla, Montserrat and the British Virgin Islands.
In Anguilla, officials reported extensive damage to the airport, hospitals, shelters and schools and said 90 percent of roads were impassable.
On Barbuda, nearly every building was damaged when the hurricane's core crossed almost directly over the island early Wednesday. About 60 percent of its roughly 1,400 residents were left homeless, Antigua and Barbuda Prime Minister Gaston Browne said.
He said roads and telecommunications systems were wrecked and recovery will take months, if not years.
"It is just really a horrendous situation," Browne said.
Additional reporting by Associated Press