Hurricane Irma

[Singularity]

I am struck obviously by the extraordinary form of Irma first but then also the extensive convective activity elsewhere in the basin with 13L now in the GOM and Jose consolidating more in the MDR. Ahead of Irma lies plenty of moist and unstable conditions plus higher oceanic heat content than is currently on tap.

So... what's to limit this hurricane apart from eye wall replacement cycles and land interaction?

Speaking of the former, the latest effort seems to have become stuck in a concentric eyewalls situation;

As for the latter, maybe some interaction of the CDO with PR & later Dominica but the model tracks generally keep the eye itself from taking much of a hit, if any. So it comes down to Cuba's mountainous southern side (particularly SE corner) but here I wonder if there could be some degree of 'density forcing' whereby air piling up against the mountains on the leading side of the cyclone achieves a high enough density to force more of a northward component to the cyclone's movement than would otherwise occur. It's debatable whether this is actually physically possible, particularly with such a large cyclone, but over the past decade I've seen a few cases here and there that at least suggest the possibility exists.

At this time a consensus between ECM and GFS (wide margins though!) would avoid all that much interaction with Cuba's mountains anyway, in which case Floridians will be in desperate need of the storm turning north as far east as possible. 

As wacky as GFS seems with the movement of the storm, at least it allows for some hope that the best-case scenario of a turn before Florida is not without chance. Unfortunately this still sees the Bahamas taking a serious beating unless something highly unforeseen knocks the cyclone's core strength down a fair way.

For all we know though, a stronger than expected development from TD 13 could change the game yet again by eroding a weakness in the ridge west of Florida and opening the door to the GOM for Irma. I am disappointed to have reason enough to write that last sentence but there it is .

 

Oh and the official dropsonde reading is 920 mb which is still 6 mb lower than found during the last flight just a few hours ago - so a steady rate of deepening continues. To be honest given all that's before me at the moment, I'd be more surprised if Irma didn't reach that most horrific benchmark of 200 mph sustained winds, to this date in history not managed by any Atlantic-basin hurricane. Therefore I sincerely hope to be as surprised as possible when I catch up on things tomorrow morning!

[AderynCoch]

Theoretically is there any limit to the strength of winds a hurricane can generate? I can see Irma surpassing Allen's 190mph record but surely it can't spend days constantly deepening and generating ever-stronger winds,.The pressure will probably keep dropping (at least until the next EWRC) but I reckon the system will soon forego an increase in wind speed for a larger wind field.

Not good whichever way you look at it. In fact, a larger wind field could easily screw over places which otherwise would escape Irma's wrath.

[Gray-Wolf]

I think the only room for 'intensification' is size of area seeing hurricane force winds? The eyewall is now up to 60 miles across so that's like a 60 mile wide F4 Tornado. When NHC say 'Catastrophic' that is what they mean!!!

[summer blizzard]

43 minutes ago, AderynCoch said:

Theoretically is there any limit to the strength of winds a hurricane can generate? I can see Irma surpassing Allen's 190mph record but surely it can't spend days constantly deepening and generating ever-stronger winds,.The pressure will probably keep dropping (at least until the next EWRC) but I reckon the system will soon forego an increase in wind speed for a larger wind field.

Not good whichever way you look at it. In fact, a larger wind field could easily screw over places which otherwise would escape Irma's wrath.

I suspect it won't hit that mark this time but once the eyewall replacement cycle completes it will give it another go. Irma has a very stable core compared to most and so right there's little to stop the deepen, replace/expand, deepen cycle. 

The atmosphere ahead is even more moist and even warmer at the surface. 

[crimsone]

Latest vortex message (22:45z) gives a pressure of 917mb, and reports concentric eyewalls at 20 and 45 miles.

HDObs from 15 mins ago extrapolate a surface pressure of 913.1mb

Edited September 5, 2017 by crimsone

[summer blizzard]

Based on satellite and NHC motion at 280 degres.. the island of Barbuda will take the core.

[crimsone]

Another dropsonde just found 917mb. Flying into the eye, the hunter picked up surface winds of 160kt, with 129 on the way back out.

[weatherobsuk]

Live night-webcam from St-Barth, Hurricane-force winds expected within 4 hours, the eyewall should be over the area in the next 6-8 hours. 

[crimsone]

NOAA9 appears to have lost its mind.

 

[philglossop]

4am BST down to 916mb.

Poor Barbuda 

[Love Snow]

 

[Ice Day]

Looking at the Barbuda weather centre, it's now reporting gusts of 135kts.

Edit. It was, it's stopped reporting.

[knocker]

 

[LightningLover]

2 minutes ago, Ice Day said:

Looking at the Barbuda weather centre, it's now reporting gusts of 135kts.

Edit. It was, it's stopped reporting.

Wow...

[Ice Day]

4 minutes ago, knocker said:

 

Bullseye hit for Barbuda then. That's very bad news.

[Iceberg]

It's difficult to see much of Barbuda standing with a population of over 1500 that's incredibly sad. 

Both gfs and meto have shifted track.i am awaiting to see if the ec follows suit but any kind of prolonged Cuba interaction is looks slim again with a possible hit on Miami and the east coast of Florida and possibly a Carolina hit. 

Pressure looks to be around 910mb ATM. 

We are entering a window of very little recon for a few hours. 

Edited September 6, 2017 by Iceberg

[knocker]

1 minute ago, Ice Day said:

Bullseye hit for Barbuda then. That's very bad news.

The whole scenario has bad news written all over it I'm afraid.

[Ice Day]

1 minute ago, knocker said:

The whole scenario has bad news written all over it I'm afraid.

Very true. 

[Iceberg]

Um 

[philglossop]

Disaster for Barbuda. Unsurprisingly all webcams are down.

[Had Worse]

http://www.ndbc.noaa.gov/station_page.php?station=BARA9

Peak of 135mph.

The readings stopped at 117.9 mph, looks like the bouy was Irma'd

Edited September 6, 2017 by Had Worse

[philglossop]

Barbuda weather station still working.

 

look at that pressure drop.....

[East_England_Stormchaser91]

23 minutes ago, knocker said:

 

The definition of hurricane is 10/10 on that capture. Devastating consequences however are inevitable 

[Iceberg]

Sizeable shift away from Cuba on ec considering its at t72. 

My interpretation is that the newly initiated larger Irma than was progged is preventing less easterly movement and is pushing the ridge More. 

[cowdog]

5 minutes ago, Iceberg said:

Sizeable shift away from Cuba on ec considering its at t72. 

My interpretation is that the newly initiated larger Irma than was progged is preventing less easterly movement and is pushing the ridge More. 

Yeah its back to its, become a 200+ mph monster and hit Florida track.

 

Edit: ROFL. at 120 its literally done a 90 degree turn and headed North straight to Miami. To say this one is unpredictable is significant understatement.

Edited September 6, 2017 by cowdog