aspen wrote:Shell Mound wrote:Structurally this is still rather disorganised. While low-level turning is evident, 99L’s western hemisphere (half) is largely devoid of convection, owing to strong mid-level shear. Certainly, the mid-level circulation is well defined, and PWATs are high, but the TUTT (PVS) is clearly preventing consolidation as of now. The TUTT is weakening and retrograding, but doing so very slowly at this time. Also, while the past several runs of the GFS have adjusted themselves to account for 99L’s short-term organisation (and resultant, convectively induced ULAC), the runs have also trended toward a stronger PVS over peninsular FL and the Yucatán Channel. This effectively offsets 99L’s better-than-expected short-term, mid-level organisation and implies that 99L will likely not strengthen significantly prior to reaching western Cuba.
That bit of shear and dry air lurking to the west of 99L is probably why no model strengthens this much in the next 48 hours before crossing Cuba into the Gulf, but since they could be underestimating how far along it is, the storm could get a little stronger than forecast. Maybe a 55-60 kt TS at a Cuba landfall.
The 00Z EC operational shows 99L impacting the Isla de la Juventud as a 1000-mb, ~45-kt TS, while the 06Z GFS suggests 988 mb/~70 kt in the same area. Splitting the difference would suggest ~60 kt/~995 mb over and/or near western Cuba. Given the better-than-anticipated presentation currently, as well as the stronger-than-expected ULL over FL, I would suggest ~55 kt/~998 mb as a good compromise, closest to—but slightly stronger than—the EC’s solution. The NHC should and probably will post Hurricane Watches for western Cuba, in consultation with the Cuban government, given the potential for 99L to near hurricane intensity as it impacts Cuba.
