Windspeed

Wow, NHC is not holding back at all, I see. Yes, intensity guidence modeling is out the roof with a very high potential that Lee reaches at least Category 4 intensity. But it's the rarest of rare to see the first official TD forecast to become a Category 4. I'm not sure it's ever happened. I certainly do not recall a previous scenario out of memory. Not even going to dig, I really do not think this has ever occurred in my lifetime.

^ The UKMET tracks would be more favorable for long-term TC intensity, as it traverses much higher OHC versus the upwelled wake of Franklin and Idalia. I don't know if that will be any kind of precursor to a swing west in the other globals on Tuesday, however.

Yes. Obviously, we're in the grey area of mid-range modeling still. We have a signal and pattern for recurve in place. But this is still far enough out that a major steering feature might not yet be correctly simulated. Hence, why, though there is some confidence, it's not chiseled out yet. We've got a pretty strong ECONUS high right now that might stick around longer than forecast and make the trough not be as strong. A mid-level trough could also cut off. Mid-level heights in the western Atlantic could model differently in a few days versus present, even if that chance will decrease if we don't see a swing by then.

Recent ASCAT. Definitely a broad center, but looks closed. Needs continued bubbling convection to tighten low-level vorticity. We'll have a TC on Tuesday.

I'm watching this region for some diurnal action tonight. It's been moistening and bubbling with low-level showers. But this is roughly the center of the broader circulation. The deeper convection to the north is increasing banding. Easterly shear appears to be easing up as well.

Yes, at one point they did. Though they did initially and correctly suggest a south of west track through the MDR due to ridge placement, that ridge was initially modeled to break down in the west with an advancing ECONUS trough. But that trough was overmodeled and lifted out while the WAR kept building west. Even after Irma was driven into the Leewards, there were more Carolina solutions in the ensembles than S. Florida. The majority did finally come west when the ECONUS trough was handled better. Irma eventually steamrolled the northern coastline of Cuba, and the rest is history. It's just good to keep in mind that though we're used to surprises with the global OPs swinging back and forth, ensembles do swing as well when out far enough in range.

At any rate, it would be easy to get comfortable on the higher probability of OTS with ensembles screaming it. But as is reiterated, we're still well beyond 5 days. Modeling has improved since 2017, but even ensembles swing and miss on MDR systems outside of that window. Just keep in mind that the evolution of the WAR and an ECONUS trough is still not in stone, even if swing back to a rebuilding ridge or cutoff in the eastern interior is trending unlikely. This ensemble from Irma is a reminder that even a strong hurricane may not go polar as fast as initially modeled. We don't even have a TC yet.

12z GFS is wasting no time. A hurricane by 54 hrs would be impressive for a global.

You know there are plenty of folks who are fascinated with TCs that do not want the destruction they can bring. Not everyone is a storm chaser. There are plenty of meteorological professionals and enthusiasts here. But obviously, the threat drives overwhelming interest if something does target land. Which makes perfect sense. A lot do not care unless a TC threatens their neck of the woods.

lol.. *shaking head* In all seriousness, It would be awesome if potential Lee becomes a classic long-tracking intense CV hurricane, but hits nothing. The ACE off this storm alone could push us into above normal territory for the remainder of the season, which would be phenomenal during a moderate-to-strong El Niño year.

This mid-to-upper flow across the MDR is certainly not El Niño'ee at present. The shear that's there is due to moderate trades and positioning Azores ridge. There is definitely westward low-level motion south of the wave axis. Some banding features evolving on the northern periphery as it looks like folding is occurring. Still some dry air in the mid-levels, but nothing that should prevent slow and steady development. It is worth noting that both globals have a TS to minimal hurricane in 48-72 hours. So we would expect to see a low-level vort get going relatively soon.

That's the thing, at 200+ hrs out, even 150+ hrs, really, trough vs ridge evolution is fluid and can change over a mere day of runs. If a pattern locks in place, fine. See if it holds. But it's just way too early. I only brought up the 18z because of that cutoff ULL placement. But it may not even be there by tomorrow's 12z. Overall, climatology says, yes, northern motion in the region north if the PR is usually OTS. But not if ridging builds back. We've got nothing else to do but explain why an OP solution is doing what it's doing. It's why we have a thread a week out from reality. It doesn't mean that will play out at all this early out.

Actually, the 18z is more of a Hugo hook, just displaced further east vs a comparable Floyd track. Floyd just drove west and turned north around ridge into weakness; no ULL influence. That mid-to-upper ULL over Florida that the GFS is now developing has to be focused upon in the coming week of runs. If potential Lee gets into the northern Leewards, near or north of PR, and drives NW, depending on timing, oh boy. That ULL develops with a New England ridge, it opens up the door for capture and landfall. This could evolve more west depending on how much ridging develops and how well-positioned the steering column plays out. Also that 300-200 hPa upper flow would be dangerous for intensity. But to caution, this is 200+ hrs out. So grain of salt.

12z GFS op missing the Leewards, however, there was a notable swing in the CONUS setup in 240-260 range vs previous runs. ULL over Florida and with increased heights over New England. The hurricane would potentially get driven near the Mid-Atlantic region. Might get interesting on this run... But, of course, this is late in the medium range. Main takeaway here is the WAR rebuilds into CONUS where previous runs it does not. See if this turns into a trend with this evening's runs.

Set of different data sets loaded. One also will use raw GFS for the UFS, while the other will simultaneously be used with sampled atmospheric data from reconnaissance. Obviously, that is only when recon is flying. Mainly to see the differences in output. That's really all I know; someone else may also want to chime in... Dr. Sundararaman (Gopal) Gopalakrishnan discussed this is a recent Weather Geeks podcast if you want to listen to him speak. It's a more evolved simulation platform with multi-outputs versus the older HWRF, which will likely be retired in a few years.

Both initial runs of the HAFS A and B have an intensifying hurricane by 100-126.

I don't think so. This is one heck of a healthy wave with evident broad turning in the low levels with an MLC already associated with the concentrated convection. With all of struggles over the MDR this season, regardless of the few systems that formed early, this one looks a go. Should be a long-tracking major hurricane. The big question isn't necessarily going to be if this can become a strong hurricane, but if it will end up a threat for the Lesser and Greater Antilles. Not mentioning the CONUS yet because it's just too early to know how/if the WAR will be there or break down.

To add to the previous post above about inland wind potential, I am curious how the core and southern semicircle of the cyclone will evolve as it increases forward motion across N.Florida and SE Georgia. The system will be interacting with the eastern trough. The potential for large swaths of downed old growth along major routes and interstates is there.

Wind interacts differently inland for a TC versus over the water or right at the coast. You get gusting bursts due to friction and turbulence. 100+ mph gusts are definitely possible if that is where the core traverses.

They still have time to leave, even if that time is short.

That doesn't seem unreasonable with this presentation... Things can change quickly for a TC when the mid-to-upper atmospheric environment cooperates. Idalia was still tilted and struggling a little over 24 hours ago.

It's no doubt an organizing outer concentric band. But the eyewall is ripping right now. By far the best it has looked. Idalia has a lot of banding features spiraling into even the outer concentric band. It very well may lead to a full on ERC, but it may still strengthen quite a bit before that can starve the current eyewall. We may see this level off intensification prior to landfall, but it could still deepen quite significantly tonight before that leveling occurs. Will be interesting to watch.

We're also at nearly 15k ft beam from Tampa. The mesos are going to stand out more. We can't see the lower vort precip in the LLC of the eyewall. It may be circular given closer range.