Major Hurricane Isaias

[NJwx85]

4 minutes ago, NavarreDon said:

Northern eyewall is upon us!




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That’s not the northern eyeball. The eyewall is still well offshore.

[vortex95]

1 hour ago, RU848789 said:

While he didn't predict this storm, per se, about a week ago, Greg Postel on TWC had a great discussion about how the huge frontal system that was progged to sweep through the SE US last weekend would stall over the very warm GOM and that pressures and low shear looked favorable for tropical development this week.  

Stalled fronts in the Gulf sometimes lead to sig HU development.  One of most notable ones was Alicia in Aug 1983 that struck HOU as a Cat 3.

[lee59]

Navarre Beach Marina has a Davis station on weatherlink, Reporting sustained 35 and gusts to 52

[mob1]

Some hurricane force gusts starting to show on personal weather stations along the immediate beaches east of Pensacola. 

[lee59]

1 minute ago, mob1 said:

Some hurricane force gusts starting to show on personal weather stations along the immediate beaches east of Pensacola. 

Yea, many reporting sustained close to 40 now with higher gusts.

[OHweather]

43 minutes ago, vortex95 said:

For a few hours now, the core has been "halved" on radar in terms of an eyewall.  I realize there is some attenuation, but if the eyewall ring was complete and intense, we'd easily be seeing a closed ring starting a few hours ago.

Ever seem intense TC at extreme range of radars?  The eye and a solid eyewall show up very well even 200 nm away!

So dry air and shear are have impacted the inner core, however, this has not impacted the central pressure or winds much at all!

This shows that the relationship between sig shear and dry air and a HU is complex and it is definitely not one-size-fits-all!  As discussed earlier, why did Lili, Opal, and Dennis weaken so much after a solid RI period in and environment not as strongly baroclinic overall than Isaias?  Actually, think about Katrina!  It went from 150 kt to 110 kt from peak onshore to landfall in ~24 hr with a ton of dry air ingested into the core and quite ragged convective structure compared to Isaias right now.  And Katrina was way larger than Isaias, so you would think it could resist dry air intrusions better.  Also, Katrina was in Aug.  The mean atmosphere as to being conducive for a strong TC that time of year is significantly better than Oct!  You don't have troughs of this magnitude cutting across the nrn Gulf in Aug!

That being said, the upper level outflow plume for Isaias is outstanding.  That unquestionably is a factor here as to keeping it from weakening.

Agree that radar has suggested a partially open eyewall since late morning…perhaps my phrasing that the inner core has “held up” wasn’t the best way to put it as it hasn’t been able to close off an eyewall for several hours, but overall it’s been a pretty steady robust half eyewall on the northern side. I do think we are starting to see signs on radar of further degradation of the core, but the northern eyewall remains nasty and the most recent dropsonde suggested a ~957mb pressure…so the pressure isn’t rising yet and that eyewall is only 2 or so hours from affecting the coast. 

As the hurricane’s motion continues bending slightly left and a bit more into the increasing shear and as core starts interacting with the rather chilly/stable air getting pulled into the storm off of land I’m guessing the eyewall slowly degrades through landfall and rapidly falls apart as it pushes inland, though for practical purposes that won’t be enough to significantly change the impacts as landfall occurs. 

These interactions between shear and storms approaching landfall is fascinating and not the same from storm to storm as you said. I thought the hurricane and global models did a pretty good job of showing the pressure holding steady or falling until some point between 18-0z, before rising rapidly beginning near landfall later this evening.  So the guidance seemed to resolve the more positive interaction we’ve seen through most of today before the negative factors finally overwhelm the storm tonight, though the timing of things changing even a few hours makes a difference so close to landfall. The HAFS models were too drastic with last minute weakening, but the HWRF and even Euro were more accurate in showing just some modest last minute weakening before landfall. 

I think that with Isaias, the storm motion paralleling the shear vector until very recently may have helped stave off its impacts by making it easier for convection to wrap around the up shear side of the storm. The very impressive upper-level divergence/outflow over very warm waters supported robust convection and deepening as well, so long as shear and dry air largely stayed out of the inner core. We’ve probably been near an equilibrium between the increasing shear and favorable thermodynamics/strong eyewall convection since late morning, with the scales gradually tipping towards weakening this evening but not fast enough to help anyone on the coast. 

In some of the storms you mentioned that weakened much more drastically before landfall, I wonder if an ERC coinciding with increasing shear led to more drastic weakening? An ERC can cause a cat 4 or 5 to weaken pretty notably even in a more favorable environment (at least temporarily)…Isaias didn’t undergo a true ERC at any point today, and I have to wonder if an ERC starting this morning or afternoon would have allowed for the storm to weaken more in the face of the increasing shear today. 

[jm1220]

115–120mph velocities not far offshore south of Pensacola. It’s elevated where the radar beam samples it but still rough impacts incoming shortly. 

[CoastalWx]

Dry air really getting at the center. Right when models had it. 
 

Interesting deep convection on the western side of the western eyewall. Wonder if dry air is causing more instability in the mid levels as it impinges in from the west and southwest. 

[VivaManchVegas]

This guy had a good gust. 

[NJwx85]

4 minutes ago, jm1220 said:

115–120mph velocities not far offshore south of Pensacola. It’s elevated where the radar beam samples it but still rough impacts incoming shortly. 

My guess is Cat 2 at landfall with numerous gusts over 100mph reported.

[NorthHillsWx]

1 hour ago, Radtechwxman said:

Temps near coast in upper 60s. That's pretty stable for hurricane. Cool and much drier air. May see quite a bit of weakening before it fully comes on shore

Doesn’t matter much now. Eyewall moving onshore 

[WxWatcher007]

5 minutes ago, CoastalWx said:

Dry air really getting at the center. Right when models had it. 
 

Interesting deep convection on the western side of the western eyewall. Wonder if dry air is causing more instability in the mid levels as it impinges in from the west and southwest. 

Yes, despite the erosion of the low level inner core, there’s still plenty of deep convection and lightning. This will still be a strong hurricane, as the NHC has said for a while now. 

[lee59]

Hard to find the eye now and most of the worst weather appears to be on the north side. Still going to be a dangerous storm

[vortex95]

34 minutes ago, Nomz said:

Significant tornado threat looks to be pretty stunted for the next few hours. Nearly zero SBCAPE is making it inland, and storms are getting choked out before they can come ashore. Already happened to a few cells coming up Apalachee Bay. 

The big tor threat is often the day after landfall, when it becomes a baroclinic system w/ low-level tropical dew points and all you needs is just breaks in the clouds for a little CAPE, and look out!

44 tors in FL from Milton on 10/9/24  This is the largest calendar day tor outbreak on record In October and among the top 5 biggest tor outbreaks in Oct in the U.S.  Milton also produced the costliest TC tor on record -- $514M from an EF3 that tracked in St Lucie and Indian River Counties.

[WxWatcher007]

60mph gusts starting to be reported along the coast. 

[dbullsfan]

About to board a flight from San Antonio to Tampa, hope they go far as hell south, want to stay far away from this cane


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[cardinalland]

140k customers without power in the region and climbing fast (was 100k 15 minutes ago)

[VivaManchVegas]

5 minutes ago, dbullsfan said:

About to board a flight from San Antonio to Tampa, hope they go far as hell south, want to stay far away from this cane


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It looks like the trailing band of storms will stay off the coast for a while and may not even get to Tampa. No delays as of now. I think you are good.

[Dunkman]

Really looks like Destin is the spot unless there’s a wobble.

[VivaManchVegas]

6 minutes ago, cardinalland said:

140k customers without power in the region and climbing fast (was 100k 15 minutes ago)

It would be interesting to know how much of that is premeditated cut outs to save the grid and make it easier to get back up and running. 

[beanskip]

Check out this nightmare. Delta flight from ATL to TLH trying to land (and not succeeding).

 

https://www.flightaware.com/live/flight/DAL1984/history/20261009/2110Z/KATL/KTLH

[NEGA_Dawg]

1 minute ago, beanskip said:

Check out this nightmare. Delta flight from ATL to TLH trying to land (and not succeeding).

 

https://www.flightaware.com/live/flight/DAL1984/history/20261009/2110Z/KATL/KTLH

That would be awful to be on that flight.