Major Developments in the Track of Hurricane Irma
Hurricane Irma continues to slowly move WSW towards St. Martin and the Virgin Islands. Tomorrow the movement is expected to shift from WSW to West and then to WNW. It is expected to pass just north of Puerto Rico, the Dominican Republic, and Haiti as a Category 4 hurricane. It is then expected to move more west than WNW and possibly make landfall on the north coast of Cuba. This is where the tracks between the GFS and Euro models begin to diverge a little.
The European model has the hurricane make a sharp 90 degree turn to the north and pass just slightly off the east coast of Florida. It then continues moving due north and makes landfall near the border of South Carolina and North Carolina as a Category 4 hurricane on Tuesday, September 12th.
The GFS model has the storm heading farther west into Cuba before making the sharp 90 degree turn to the north, so it has it passing directly over the Florida Keys and into the west coast of Florida. as a Category 4 hurricane on Monday, September 11th. It then continues to head due north, which would take it directly into the center of Florida. This would bring widespread amounts of 10 to 20 inches of rain with catastrophic wind damage. There will still be slight changes in the track since potential landfall in the United States is still 6 to 8 days away.
The following image is from the GFS model this morning, and it's showing landfall of Hurricane Irma in Florida (the wind speeds indicated are not surface-level sustained winds, but those are the wind speeds higher in the atmosphere. However, those speeds generally indicate the maximum wind gust possible at the surface. Also, the wind speeds are in knots, so multiply that by 1.15 to convert to mph.)
Image from tropicaltidbits.com
The following image shows the Euro ensembles, which takes the initial conditions from the operational run of the Euro and varies them slightly to cover a range of possible tracks if the conditions were slightly different.