Major Hurricane Irma

[OUGrad05]

1 minute ago, KPITSnow said:

Perhaps this is anecdotal, but it seems that in situations where a storm maxes at high end cat 4 or 5, if it loses its inner core structure it rarely ever recovers no matter how favorable conditions are?

 

If I am wrong, maybe one of the mets can correct me, but I think it is something to watch?

 

That's a fair point, there are some storms that suffered structural issues and recovered but in many cases they don't.  Although I'm not sure what will totally disrupt this core?  Seems to me with the forecast environment it may be weakening at FL landfall but I'm not seeing something that could disrupt the core to the point that it isn't a cat4 or 5 at landfall.

[Wow]

12z hurricane models

[jpeters3]

1 minute ago, Drz1111 said:

This isn't worth noting.  The HMON is performing horribly and isn't even being referred to in NHC discussions.

Please don't make pretentious posts like this.  Any model guidance is useful (or at least relevant) to this discussion.

[lwg8tr0514]

6 minutes ago, NJwx85 said:

It's worth noting that the 06z HMON shows Irma temporarily struggling a bit over the next day or so before ramping back up to Category 5 tomorrow night. Peaks back out with 175mph winds near the FL straights before coming very close to landfall near Palm Beach as a cat 5.

That's a very bad scenario, could be the most people impacted by a major hurricane in history, wresting that title from New Orleans and Katrina or Houston and Harvey.  Could be damage in 10's of billions as 5-6 million people are affected on the SE Florida coast.  My mother lives in Hollywood Florida on a 5th floor of a condo with old windows and no shutters and my daughter in a wood frame house 3 miles from the beach in Northern Palm Beach county. Very worried.

[KPITSnow]

5 minutes ago, jpeters3 said:

 

Hurricane Ivan (and Allen for that matter) went back and forth from Cat 4 to Cat 5 3 times:

https://en.wikipedia.org/wiki/Hurricane_Ivan#/media/File:Ivan_2004_track.png

Well was thinking more along the lines of where for whatever reason...dry air intrusion, land interaction, the eye degrades or fills in. I know we have seen  before where we have a healthy looking cat 4 or 5, and all of a sudden the core degrades. 

 

Ivan, at least, from what I remember, never had a degradation like that till near landfall. 

 

We we will see what happens, though as has been noted by many on here there really aren't any factors that would cause this.

[Buddy1987]

4 minutes ago, Wow said:

12z hurricane models

Wow very tight clustering now in showing a track literally scraping along the MIA coast or just off shore and then landfall in between Hilton Head and CHS. 

[Windspeed]

 

 

Again, I don't necessarily think a decrease in wind is guaranteed.  There have been many large storms (Katrina) a similar latitudes that achieved very strong sustained winds.  The main players are going to be internal processes (eyewall replacement cycles), and vertical shear (I suspect there is a bit of Wly or NWly shear right now due to outflow restriction on that side of the storm).

 

A decrease in pressure gradient is expected due to a decrease in background pressures as the weakness expands and steering ridge erodes. Therefore wind speeds would come down if Irma maintains around 915 to 920 mb central pressure. If the eyewall remains intense or reintensifies after a structural change, it would still be capable of producing Cat 5 sustained winds, 180+ mph just seems unlikely unless it were to have an vigorously low pressure drop to sub 900 mb readings. A potentially larger hurricane might be difficult to pull that off, but not impossible given SSTs, low shear and excellent outflow.

 

[jpeters3]

2 minutes ago, KPITSnow said:

Well was thinking more along the lines of where for whatever reason...dry air intrusion, land interaction, the eye degrades or fills in. I know we have seen  before where we have a healthy looking cat 4 or 5, and all of a sudden the core degrades. 

 

Ivan, at least, from what I remember, never had a degradation like that till near landfall. 

 

We we will see what happens, though as has been noted by many on here there really aren't any factors that would cause this.

It seems like there may be a few of those (at least shear) over the next few days.  I suspect that the reason is a combination of ERCs and the low likelihood that a given storm will remain in an environment that supports cat 5 intensity for an extended period of time.

[NJwx85]

9 minutes ago, Wow said:

12z hurricane models

Yikes, they almost all have at least the Western eyewall coming onshore near MIA/FLL.

[lwg8tr0514]

1 minute ago, Buddy1987 said:

Wow very tight clustering now in showing a track literally scraping along the MIA coast or just off shore and then landfall in between Hilton Head and CHS. 

Being a native to Fort Lauderdale, that's a worst case scenario, I would say 70% of the population lives within 25 miles of the coast down there, the storm entering Port of Miami going inland 10-20 miles and scuttling up through Broward, Dade, Palm Beach and Martin counties as a 4-5 and then exiting, we would see catastrophic damage, making Andrew look tame. Andrew hit southern Dade county and missed the heavily populated parts. This is like a direct hit on Houston, Philadelphia or Phoenix.  No good way to spin this, at this point. Arguing about ERCs and if the winds will be 155 or 165 at landfall is a side issue.

[bluewave]

Remarkable Euro performance so far with only about a 60 mile track error with the 72 hr forecast.

 

 

 

[jpeters3]

6 minutes ago, Windspeed said:

34 minutes ago, jpeters3 said:

 

Again, I don't necessarily think a decrease in wind is guaranteed.  There have been many large storms (Katrina) a similar latitudes that achieved very strong sustained winds.  The main players are going to be internal processes (eyewall replacement cycles), and vertical shear (I suspect there is a bit of Wly or NWly shear right now due to outflow restriction on that side of the storm).
 

A decrease in pressure gradient is expected due to a decrease in background pressures as the weakness expands and steering ridge erodes. Therefore wind speeds would come down if Irma maintains around 915 to 920 mb pressure. If the eyewall remains intense or reintensifies after a structural change, it would still be capable of producing Cat 5 winds, 180+ just seems unlikely unless it were to have an vigorously low pressure drop to sub 900 mb readings. A potentially larger hurricane might be difficult to pull that off, but not impossible given SSTs, low shear and excellent outflow.

Remember though that the part of the pressure gradient in a hurricane that is responsible for the fastest winds is confined to the region right around the core, which may be less sensitive than you think to changes in the pressure of the far environment.  My point is that processes like shear or internal restructuring (ERC) are going to be the first order regulators of intensity - not necessarily ambient pressure or storm size (this is just my view).

Also, simple hydrostatic arguments can show that the latent heat release (and eye subsidence) is related to the change in pressure between a TC core and its surrounding environment - not the surface pressure value.  This means that if the TC maintains the same core temperature when moved to a region of lower ambient pressures, the TC's central pressure should go down accordingly.

[Buddy1987]

Just now, lwg8tr0514 said:

Being a native to Fort Lauderdale, that's a worst case scenario, I would say 70% of the population lives within 25 miles of the coast down there, the storm entering Port of Miami going inland 10-20 miles and scuttling up through Broward, Dade, Palm Beach and Martin counties as a 4-5 and then exiting, we would see catastrophic damage, making Andrew look tame. Andrew hit southern Dade county and missed the heavily populated parts. This is like a direct hit on Houston, Philadelphia or Phoenix.  No good way to spin this, at this point. Arguing about ERCs and if the winds will be 155 or 165 at landfall is a side issue.

I couldn't agree more, especially with any portion of the eyewall making it onshore in any fashion is catastrophic. My aunt lived in Miami when Andrew hit and she said it was the scariest thing to date she has ever been through. She is now 87 y/o, so goes to show you the raw power of these animals.

[NavarreDon]

6 minutes ago, KPITSnow said:

Well was thinking more along the lines of where for whatever reason...dry air intrusion, land interaction, the eye degrades or fills in. I know we have seen  before where we have a healthy looking cat 4 or 5, and all of a sudden the core degrades. 

 

Ivan, at least, from what I remember, never had a degradation like that till near landfall. 

 

We we will see what happens, though as has been noted by many on here there really aren't any factors that would cause this.

Full NHC write up on Ivan: http://www.nhc.noaa.gov/data/tcr/AL092004_Ivan.pdf

 

[NJwx85]

Just about all the 12z statistical guidance keeps Irma at Cat 5 or high end Cat 4 through 84hrs. 

 

[cwc]

1 hour ago, jaxjagman said:

If this verifies, comes ashore at Ocean Reef Club, where the crappy houses start in the million $ range.  https://www.oceanreef.com/

then direct hit on Turkey Point nuclear power plant (which also took the direct hit from Andrew - $90M in damage to the plant alone from that strike)

[Quincy]

Euro ensemble spread through 84 hours:

[Ralph Wiggum]

Just about all the 12z statistical guidance keeps Irma at Cat 5 or high end Cat 4 through 84hrs. 

 

Ugh. This is not good, not that I am expressing anything we already didnt know.

So what is our best hope at this point? A track which makes LF west of Key Largo then stays inland? A track that clips Cuba barely and weakens slightly? A track that remains East of FL?

Im in the camp that there really is no good modeled solution at this point, just want to hear other thoughts. Even if it skirts FL to the East its like robbing Peter to pay Paul as it remains strong over warm water before slamming SC(?).

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[OUGrad05]

2 minutes ago, Quincy said:

Euro ensemble spread through 84 hours:

That is a large spread and there's a lot of people that do not realize that spread exists.  There is still a tremendous amount of uncertainty on track.

[JC-CT]

Ugh. This is not good, not that I am expressing anything we already didnt know.

So what is our best hope at this point? A track which makes LF west of Key Largo then stays inland? A track that clips Cuba barely and weakens slightly? A track that remains East of FL?

Im in the camp that there really is no good modeled solution at this point, just want to hear other thoughts. Even if it skirts FL to the East its like robbing Peter to pay Paul as it remains strong over warm water before slamming SC(?).

Sent from my LG-V410 using Tapatalk

Best case is it gets shredded by Cuba

[dmillz25]

Family from Puerto Plata DR report heavy rain and tropical storm force winds so far

[NJwx85]

4 minutes ago, Ralph Wiggum said:

Ugh. This is not good, not that I am expressing anything we already didnt know.

So what is our best hope at this point? A track which makes LF west of Key Largo then stays inland? A track that clips Cuba barely and weakens slightly? A track that remains East of FL?

Im in the camp that there really is no good modeled solution at this point, just want to hear other thoughts. Even if it skirts FL to the East its like robbing Peter to pay Paul as it remains strong over warm water before slamming SC(?).

Sent from my LG-V410 using Tapatalk
 

The best case scenario right now is that the eye stays far enough East that is misses most of Florida, and then hits the Carolinas as a much weaker but still formidable cane.

[klw]

Interesting outer ring now showing up on MIMIC.  I had not noticed this before with this storm but can only find a GIF and not a still of the end.

 

[NJwx85]

1 minute ago, JC-CT said:

5 minutes ago, Ralph Wiggum said:

Ugh. This is not good, not that I am expressing anything we already didnt know.

So what is our best hope at this point? A track which makes LF west of Key Largo then stays inland? A track that clips Cuba barely and weakens slightly? A track that remains East of FL?

Im in the camp that there really is no good modeled solution at this point, just want to hear other thoughts. Even if it skirts FL to the East its like robbing Peter to pay Paul as it remains strong over warm water before slamming SC(?).

Sent from my LG-V410 using Tapatalk
 

Best case is it gets shredded by Cuba

The chances of that happening are low and decreasing by the hour.

[rolltide_130]

3 minutes ago, Ralph Wiggum said:

Ugh. This is not good, not that I am expressing anything we already didnt know.

So what is our best hope at this point? A track which makes LF west of Key Largo then stays inland? A track that clips Cuba barely and weakens slightly? A track that remains East of FL?

Im in the camp that there really is no good modeled solution at this point, just want to hear other thoughts. Even if it skirts FL to the East its like robbing Peter to pay Paul as it remains strong over warm water before slamming SC(?).

Sent from my LG-V410 using Tapatalk
 

Honestly, your best hope is a total recurve which still isn't completely impossible, but it's not looking too hopeful by now either. 

 

Beyond that, there's really not many good options. Brushing Cuba and then landfalling in the swamps of SW FL is probably the best one, but the Keys would still get demolished. 

[RichardJacks]

Here is a great illustration I found on twitter

 

[friedmators]

4 minutes ago, klw said:

Interesting outer ring now showing up on MIMIC.  Had not seen this before with this one but can only find a GIF and not a still of the end.

 

I was just going to make a post about this.  Have to assume ERC but its a good 75 km away which would imply a long process.

EDIT: ERC analysis shows brightness around 75km.

[adiabatic13]

GOES16...warming, shrinking and more symmetrical eye, no signs of weakening evident at the moment

[Casualbrain]

1 minute ago, RichardJacks said:

Here is a great illustration I found on twitter

 

And here's a good steering current animation that helps understand this pic http://tropic.ssec.wisc.edu/real-time/atlantic/movies/wg8dlm1/wg8dlm1_loop.html

 

[CoastalWx]

43 minutes ago, jpeters3 said:

 

I'll agree that an expanding wind field is likely once the system begins to interact with the baroclinic zone and starts undergoing ET.  Seems to me based on model guidance though that the forecast for decreasing intensity in models is (1) because they generally don't show maintained intensity Cat 5 for whatever dynamical or numerical reasons (they've been showing weakening for a day and a half), and (2) because they are fairly well anti-correlated with vertical shear (which should gradually increase over the next few days).  Human forecasts (NHC) have shown decreasing intensity in accordance with model guidance, and the low statistical likelihood that TCs maintain 150 kt + intensity for an extended period of time.
 

Great post. Thanks for the one stop shop graphic!