I'm a little surprised you didn't factor the longwave pattern into Irene. As early as yesterday's 06Z run; not current 06Z run mentioned the possibility of strong ridging over Alaska which would induce a deeper longwave trof over the NW to Mid US thus induce stronger ridging over the W Atlc which it appears to be what's in play, though the new run doesn't indicate as strong a trof in the mid US, iit continues to amplify the SE ridge through 120 hours. Thus far the 06Z GFS is the consensus model of choice with current features. Irene continues to move due west as of this typing and appears on satellite to be quite symmetrical and thunderstorms are firing to her SW and N with very cold tops. Whether that continues, remains to be seen, but it does appear it's becoming more organized early this morning. I think if the evolution of the longwave pattern pans out, Irene should continue on a more west and southerly track around the perphery of the ridge.