WxWatcher007

Recon is heading in for another pass.

Sorry, here was the D3 text and categorical risk. Doesn't say tor risk but I think we know... ...Delmarva into the Carolinas... Considerable strengthening of the deep-layer wind field is forecast on Sunday in advance of the midlevel trough. However, considerable cloud cover and areas of precipitation appear likely to limit air mass destabilization within the poleward-expanding warm sector. Nonetheless, boundary-layer dewpoints in the upper 60s to mid 70s will support pockets of modest instability, especially in areas where cloud breaks may occur. And given the presence of relatively strong low-level and deep-layer shear, a conditional risk for severe storms capable of damaging winds and perhaps a few tornadoes will exist Sunday into Sunday evening. Higher severe weather probabilities may be required in later forecasts if subsequent model data indicate greater instability than that currently depicted.

Peak Season Forecast (Aug 20-Oct 20) Named Storms: 5 (6) Hurricanes: 3 (1) Major Hurricanes: 1 (1) Dolly, Edouard, Fay, Gonzalo, Hanna, Isaias (MH) Homebrew delivers again...

Yeah, very tough call. Just a few hours made the difference here, though it's incredibly impressive how well GDM has been through the entirety of this one. Like you said in another post, it was easy to hedge east for this one, and GDM never backed down on a higher end peak. Well, keep in mind that Idalia hit one of the least populated areas of the state. Idalia's eyewall was legit, but less damage=less need for retirement. That won't be the case with this one, even if it's weakening at the end, because it's hitting real population centers. Not to mention the yet to be seen inland impacts in the south. Agree with this too. There's going to be a line of discussion here tonight about why we're not seeing G125 across the landfall zone and it'll be because 1) that's not how things work lol and 2) the strongest winds in a decaying core may be concentrated in a few spots. Still bad to be clear with other impacts and with wind itself, but as I've found, eyewall dynamics and impacts are more mesoscale than people tend to realize.

7:20 AM CDT Fri Oct 09 Location: 27.0°N 87.6°W Moving: NNE at 15 mph Min pressure: 959 mb Max sustained: 120 mph

Latest recon finds 117-120kt FL winds. 959.3mb pressure extrapolated. 960mb dropsonde in the center with a 6kt wind.

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.

On the cusp of a major--the only one of the season--which would be a huge coup for my peak season forecast.

Marginal D3 SPC outlook right now but with a 5% tor risk. Good chance there's an upgrade as we get closer if the track holds.

With that deep ring of convection…

Idk…I’ve been a believer in GDM and the ensembles get bullish tonight on the peak. LF intensity is anyone’s guess but I’m probably with you on 90-95mph at landfall. Love me some tropical sunsets. Be safe down there. I’m not chasing this one (wife’s birthday lol) New one should be out there in a few hours. Perfect timing imo.

980.3mb extrapolated. Pressure falls continue. As the deep convection continues over the center we are probably on the cusp of significant intensification, even as you see some more hostile conditions on the western edge of the system. It's a race between this current intensification trend and when the conditions ultimately disrupt the center.

Waiting on one more center pass before going to bed...

You can see in this IR image that the environment isn't pristine, but there's just enough of a window to allow for the inner core to take shape. Now we're in the intensification phase and if the core can remain shielded from the shear and drier air to the west this has a chance to become a major before shear takes its toll on Friday. As for impacts beyond landfall, meaningful rain continues to look likely up and down the east coast, as the remnants of Isaias seem to get caught up in a subtle trough and get kicked eastward as it gains forward speed post landfall. It doesn't look like flooding rain, but I think we need a little more time to get a sense of the rain potential. What continues to be interesting to me is the potential for at least some favorable conditions for severe storms, especially if the timing ends up a bit slower and the mid level center passes to our west during daytime Sunday. From the SPC: For Sun/D5, the shortwave trough and remnants of the tropical cyclone will generally move northeastward toward the Appalachians and toward the Carolinas and southern Mid Atlantic. It is possible that the upper system outruns the unstable warm sector, but at least a low end chance of severe is not out of the question.

And with that, my peak season forecast grade improves. Might get two H's now that the NHC won't have to worry about postseason futility records with Fay. Peak Season Forecast (Aug 20-Oct 20) Named Storms: 5 (6) Hurricanes: 3 (1) Major Hurricanes: 1 (0) Dolly, Edouard, Fay, Gonzalo, Hanna, Isaias (H)

Was just coming to post about the dropsondes. Let's see what the next pass looks like but that was a substantial drop in pressure between center fixes.

Oh no not at all. This is probably modest impact at best. Severe risk tbd.

982mb dropsonde

On the cusp at 11pm

Remember this one? Nobody in CT does. Mass special.

Yeah, good recall. That was highly impactful.

Cyan ring there. That’s significant.

Great tweet from Andy

Yeah that’s something to watch

What a difference a few hours make. From a broad and weak low to a clearly aligning and tighter center. Winds are responding almost immediately. If it can avoid dry air entrainment as it organizes today, I would favor a peak at major status.