Several hundred troops from the Royal Marines and Royal Engineers from the Army will travel to the region on RAF Transporter planes and are expected to deploy in the next 24 hours.
The Ministry of Defence says it is making an assessment as to where to fly the British military task group.
The category five storm is continuing to tear a deadly trail through the Caribbean, at least 13 people have been killed, with St Martin and Barbuda particularly badly hit.
It has already left thousands homeless after destroying buildings and uprooting trees.
The supply ship RFA Mounts Bay has already been deployed to help deal with the aftermath of Hurricane Irma with 40 Royal Marines on board, as well as army engineers and equipment.
Defence Secretary Sir Michael Fallon said:
“In the face of such devastation, I have authorised the deployment of a task group to region. Over the next 24 hours troops and engineers held at high readiness in the UK will deploy with helicopters to support the relief effort. I am also sending a command headquarters to co-ordinate our efforts.”
“With the danger posed by Hurricane Jose which will hit areas already affected by the storms we are diverting a second ship to the Caribbean, our flagship HMS ocean, to bring the help that will be needed in reconstruction after the hurricanes have passes.”
Team Rubicon UK (TRUK), a group that harnesses the experience of military veterans to aid disaster relief missions, is moving to a forward position in response to the storm.
Last week, HMS Ocean departed Plymouth to spend the next few months in the Mediterranean on NATO operations before she is decommissioned next year.
She will be replaced by the far larger Queen Elizabeth aircraft carrier in 2020.