The NHC intensity estimates DO include forward motion factored into them. It is inherent to recon measurements and for recurving storms they will take it into account when determining storm intensity. The other posts are incorrect in assuming that the forward speed needs to be added or subtracted into the NHC intensity.

The clearest example comes from the last discussion on Wilma:
"THE INITIAL INTENSITY OF 75 KT IS BASED ON A SATELLITE INTENSITY FROM TAFB AND RESPECT FOR THE RAPID MOTION." (http://www.nhc.noaa.gov/archive/2005/dis/al242005.discus.043.shtml?)

Most storms where forward motion needs to be accounted for are storms that are rapidly weakening in an extratropical environment and undergoing extratropical transition, for which storm asymmetry is a very important consideration. The NHC knows this and takes this into account in their estimates.