Discussion: HWRF indicates Fiona may intensify to a 938-939 MH intense hurricane Thursday night (Fig. 1). If so, Fiona should reach the category-4 intense hurricane level. The old Saffir-Simpson Scale indicated <945 MB qualifies as a category-4 storm. Given the warm water (Fig. 2) and the convective tail into the tropics (Fig. 3), this system should have no problem getting close to this level of intensity. The time of 938-939 MB occurs as Fiona begins a northeastward turn on Thursday.
Fig. 1: HWRF model projects 938.9 MB surface pressure for Fiona at 5AM EDT on Friday which should produce a category-4 intensity major hurricane.
Fig. 2: Fiona is forecast to drift through 85-86F water which easily provides enough fuel for Fiona to become a major hurricane.
Fig. 3: The tropical convection “tail” extending to the deep tropics is a classic intensification signature for Fiona once moving away from land.