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Isaias is on the cusp of becoming a major hurricane this morning, and as you all know by now it is explicitly forecast to become a major shortly. Although not a pristine satellite appearance, Isaias from both satellite and recon is clearly an intensifying hurricane at this hour with an eye, deep convection continuing to wrap upshear in bursts, and rapidly falling pressure in between center fixes as a result. While the season has been defined by futility overall, with both Fay and Edouard we had systems that were able to maximize their limited geographic environment to pop, and Isaias is the best example of a system taking advantage of the narrowest of windows for development and intensification this season. If Isaias were moving in any other heading, it would be getting annihilated right now. Isaias is the beneficiary of excellent divergence and a relative heading that precludes shear so far from disrupting the increasingly strong inner core. This has also allowed the hurricane to avoid disruption from dry air entrainment. A few days ago, that was a key question for me as the core was establishing itself. Normally a northern Gulf landfall, especially this time of year, features last minute continental air disrupting things, and while that may eventually erode part of the system, that's not happening right now. The resilience of Isaias will be tested in the coming hours, and if you're still reading here's the real thrust of the post: the NHC is right to be concerned about a delay in weakening. I do still think that shear will eventually disrupt Isaias, but it may not happen until landfall is occurring. Operationally, that may mean it's difficult for the NHC to confirm weakening as the center is moving onshore. More importantly, in an expanding wind field, it could be the case that we see the intensification plateau later followed by pressure rises and then winds weakening. For folks along the coast, any lag between the impact of shear and weakening may lead to a C3 landfall. This is a razor's edge forecast. It seems clear that unlike many of the recent Gulf examples there will not be intensification up to landfall, but weakening may be blunted or delayed. The latest HAFS A & B both show more intensification before some weakening--right at landfall. Both essentially have a major landfall in the next 12 hours. Perhaps more significantly, the GDM, which I've been raving about for two years now and with good reason--it's by far the best hurricane ensemble--shows very little change in intensity until landfall is effectively occurring. Pay less attention to intensity and more to whether there's weakening evident and when. At this point, I think folks in the landfall zone should be prepared for a C3 impact. It likely won't be at its peak, which is important from an impacts standpoint (the storms intensifying at landfall tend to "feel" worse than ones weakening at the same intensity), but between surge, rainfall, and a likely significant severe weather threat, this is likely to be a highly impactful hurricane. I'm not there for this one, but stay safe to everyone down there.

It's a tough call because like they said in the statement, a 6-hour delay in the onset of shear could mean 20mph in LF intensity....so they are making the right call hedging more intense. They have to balance the need to disseminate as precise a forecast as possible to the public with the need to convey a sense of urgency commensurate with the worst possible outcome that can be reasonably expected.

Looks like recon quit transmitting data?

This pass will decide if it gets the upgrade. I would be shocked if it didn’t find cat 3-worthy winds

Andrew intensified rapidly before landfall in south florida from the east. Stick to making bad sports takes.

Yes they will Don. I wouldn't be surprised to see a Special Statement within the hour.

Yea, I’m not feeling good about this at all. Surprising mix of opinions locally. Some are just saying as “long as it isn’t Helene” but this is still a lot of rain and we haven’t been tested much since. I’m worried, especially along the escarpment.

HAFS-B has gone from a decapitated, essentially nor Easter, landfall to a cat 3 with eyewall intact as it crosses the coast. Buckle up coastal residents

With better upper air conditions than this one has. Shear and dry air are making a beeline right into this one. Will it have enough time to weaken a lot is one question but it’s almost certain this one weakens coming in.

If recon verifies a major before the 10:00AM update will NHC issue a special statement? .

True, but WB 3K NAM is slower than EURO...more to come at hr 60.

Like I said to you a few days ago, always hedge east when a poleward moving tropical entity is interacting with a mid latitude system....going with the bots was a tremendously easy call. That said, there are no absolutes, so I get the conflicting thoughts by some.

Models keep trending up with rain for us as the storm is slightly east of forecast track each cycle.

Recency bias.

What a win for GDM weathernextv3. It’s getting scary how good it is.

Yes, this is what I was getting at....I understand that the baseline warming elevates that critical threshold for convection, but the warming across the eastern Pacific was lagging the west Pacific, so these recent potent El Nino events are part of a concerted effort to neutralize that...especially this latter, record surge. It's a battle, so the expression of warm ENSO has been masked to an extent, which is what @ensonerd1233e343was driving at. The antecedent warm west/cool east stratification and the record warm ENSO push are two competing forces, the latter attempting to restore a prior baseline in the midst of rapid GW. You're right...no one knows for sure how this will all work out, and I appreciate the different perspectives.

Now show the nam3k lol

if you want to play that game then harvey andrew michael and a bunch of other storms did intensify

Euro caved and came north with the heavy rain Sunday night

Think they are awaiting recon but that is almost undeniably a major at the moment. I’d venture to guess recon emphatically concludes the same

You better be prepared to suit up tomorrow night!

Opal in 1995, Dennis in 2005, and the list goes on.

WB 6Z EURO and AI

Remains Cat 2 at the 8am intermediate advisory. A bit surprising to be honest. Pressure down to 958mb