This is an excerpt from the 4AM EST-Saturday Advisory. It may answer some or all of the above question.~danielw

THE GLOBAL MODELS DISSIPATE GAMMA OR KEEP IT TRAPPED IN THE WESTERN CARIBBEAN SEA DURING THE NEXT 5 DAYS... WHICH SEEMS UNREASONABLE GIVEN THE VERTICALLY DEEP CIRCULATION NOTED IN THE 00Z UPPER-AIR DATA.

AS SUCH...THE OFFICIAL FORECAST TRACK LEANS MORE TOWARD THE GFDL SOLUTION SINCE THAT MODEL MAINTAINS A DEEP TROPICAL CYCLONE THROUGH 120 HOURS.

SINCE SIGNIFICANT VERTICAL SHEAR IS FORECAST TO REMAIN ACROSS GAMMA THROUGHOUT THE PERIOD... ONLY SLIGHT INTENSIFICATION IS EXPECTED.
THE OFFICIAL FORECAST IS A BLEND OF THE GFDL AND SHIPS MODELS.

http://www.nhc.noaa.gov/text/refresh/MIATCDAT2+shtml/190833.shtml