irma category head towards leeward islands caribbean expect move near northern part region tuesday night wednesday u.s. national hurricane center say hurricane irma 320 miles 515 km east leeward islands pack maximum sustain wind 150 mph 240 km/h miami-based weather forecaster say swell generate irma affect northern leeward islands puerto rico u.s. british virgin islands next several days nhc say dangerous hurricane irma move towards caribbean islands nhc