National Hurricane Center discussion:

The environment is favorable for Irma to maintain its category 4
status, and only unpredictable eyewall replacement cycles could
result in intensity fluctuations during the next 48 hours. The
interaction of the hurricane's circulation with Cuba will probably
not result in any relevant change in intensity. In summary, the NHC
forecast brings Irma near south Florida as a category 4 hurricane.
After landfall, interaction with land and an increase in wind shear
should induce gradual weakening.

Satellite images and radar fixes from Cuba indicate that Irma has
slowed down and is now moving toward the west or 280 degrees at
about 10 kt. The hurricane should continue on this track for the
next 12 hours to 24 hours, and this track will bring the core of
Irma very close to the north coast of Cuba. After that time, Irma
should reach the southwestern edge of the subtropical high and begin
to move toward the northwest and north-northwest toward the Florida
peninsula. The precise moment of this turn is still uncertain, and
that is why NHC emphasizes that nobody should focus on the exact
track of the center. This afternoon's NHC forecast was again
adjusted a little bit westward following the trend of the ECMWF
model and both the HFIP corrected consensus and the FSU
Superensemble. In fact, these 3 aids continued to be tightly packed.