ATL: IRMA - Post-Tropical - Discussion

[Blinhart]

Did I just hear correctly some idiots were staying on a houseboat in Key West???? If so, I'm pretty sure we can count those as casualties of this massive storm, unfortunately.

[PandaCitrus]

The very broad wind field is increasing the storm surge risk. Water is piling up.

[jasons2k]

Even thought the eye has been offshore for several hours, it's only just now that the entire core is offshore, unimpeded by land friction, and has all that warm water for fuel. I really don't see any reason why Irma cannot further deepen until she hits the shear, which is still a ways off. Plenty of time to get back to a Cat 4. The surge will be beyond imagination.

[LAwxrgal]

I think the double wind maxima is causing Irma's winds not to have caught up to her pressure.

[Ptarmigan]

I'm getting Charley flashbacks with the NHC having to put out an emergency advisory with Charley bombing to Cat 4 and going to Punta Gorda.

Irma bombing to Cat 4 and moving west of track west of Tampa Bay and piling much greater than expected 15-20 feet of surge is a nightmare scenario.

A major hurricane hitting Tampa Bay would be worse than hurricane hitting Miami.

Tampa Bay area rated nation's most vulnerable to hurricane storm surge
http://www.tampabay.com/news/weather/hu ... ge/2249075

[WxGuy1]

I can almost guarantee you that this storm, regardless of up to date observations and forecasts, will intensify and at least be of category 4 intensity off the SW Fl coast. IMO

Other than the warm SSTs, why do you think that? When is the last time recon sampled legit Cat 4 winds? Irma should only have ~12 hours left over water, and the storm has weakened and/or held steady now for the past ~24 hours. Of course, anything is *possible*, but the NHC isn't tasked with making forecasts for all of the different possibilities. They assess what they think is the most likely outcome, and it seems that time is running out for the storm o reintensify to the level previously forecast. Again, it's possible RI may begin, but that doesn't seem to be the most likely evolution. As others have noted, it seems likely that, if the track is actually just west of Naples and/or Tampa, surge will be a bigger story than extremely high winds. If Irma makes landfall in the Everglades (probably the best case scenario, honestly), the surge in the Tampa area will probably be less since the strongest winds will be from the northeast, north, and, eventually, northwest. At least at closest approach, this would mean the winds would be offshore or along-shore. If the path is ever just a hair west of those areas, the surge may be very destructive. Follow the local NWS and NHC forecasts, though!

Dewpoints in the Florida panhandle are currently in the *50s*, and that dry air (precipitable water < 1.50") is into the central Gulf. By the time Irma gets to the latitude of Tampa, it looks like it will begin to wrap some of the dry air into the circulation.


From the Key West radar, it looks like there are still two eyewalls, with the inner eyewall still partly there. I haven't looked at recon much lately other than to notice that FL and SFMR winds are way lower than they have been in Irma for several days, so I'm not sure if recon shows evidence of double wind maxima.

[MrJames]

Latest shear map

[Alyono]

I don't think there will be significant shear until this is north of Ft. Myers. First, the shear enhances the outflow. Them, the storm gets sheared. However, given how large this is, I don't see a rapid weakening due to the shear. Don't think this will be sheared as bad as Charley was after landfall, or Lili before landfall

[Frank P]

Not model thread but worth noting gfs shifted tad east from 18z

but at 18 hours it shifted equally a tad west..

[Zarniwoop]

Even thought the eye has been offshore for several hours, it's only just now that the entire core is offshore, unimpeded by land friction, and has all that warm water for fuel. I really don't see any reason why Irma cannot further deepen until she hits the shear, which is still a ways off. Plenty of time to get back to a Cat 4. The surge will be beyond imagination.

Double windfield maxima.

Last one took 24+ hours to resolve.

[1900hurricane]

Here's a couple of my recent Twitter posts concerning Irma. Basically just me thinking aloud and speculating.

 https://twitter.com/1900hurricane/status/906719033730498562



 https://twitter.com/1900hurricane/status/906720516425347074



 https://twitter.com/1900hurricane/status/906721845403152384



 https://twitter.com/1900hurricane/status/906725265358905344

[supercane4867]

 https://twitter.com/NWSAtlanta/status/906716024136982528

Well, here in Atlanta suburbs many gas stations are running out of gas start from yesterday. There're also lots of cars on the streets with Floridian plates. We are worried about possible power outages and unfortunately it's quite likely at this point. But at least there no trees around my house since they're already brought down by past thunderstorms.

And when is the last time a TS/hurricane watch issued for Atlanta metro? Opal 95?

[p1nheadlarry]

If Irma goes west of Key West, going to be bad up here.

[Bamagirl2408]

Slightly west of Key West or direct hit? Thoughts?

[LAwxrgal]

Even thought the eye has been offshore for several hours, it's only just now that the entire core is offshore, unimpeded by land friction, and has all that warm water for fuel. I really don't see any reason why Irma cannot further deepen until she hits the shear, which is still a ways off. Plenty of time to get back to a Cat 4. The surge will be beyond imagination.

Double windfield maxima.

Last one took 24+ hours to resolve.

And I'm not sure she has 24 hours until landfall.

[bjackrian]

I think the Marathon AWOS may have gone out. Don't know if it's mechanical, communication, or power issues, but no update in >1 hour. Had been updating quite frequently with wind, vis, ceiling changes.

https://www.aviationweather.gov/metar/data?ids=KMTH&format=raw&date=0&hours=36

Edit: and of course, as soon as I post, it updates. Peak gust of 54 kt in last hour.

[MrStormX]

Harvey, and now Irma have all but proved to me that the Saffir Simpson Hurricane Scale is a broken way of categorizing storms. Categorizing an event on wind speed alone is patently dangerous, and creates a skewed perception of reality by the layperson. Irma might not be a category 4 or 5 storm any longer, but it certainly has an expansive hurricane force wind field that is atypical of you average land-falling cat 2/3 and a storm surge threat that might be catastrophic under the right conditions. It is time to do away with this scale as the sole way of categorizing an operational tropical cyclone, and institute a new system that will better relay the specific threats of a storm to the public.

[1900hurricane]

GOES-16 has warm medium grey in the eye once again, the first time since prior to the Cuba encounter.

[got ants?]

Just now getting another feeder band. Unlike the previous ones, its lacking wing. BUT, its making it up with rain. Its a white out and I cannot see the neighbors house across the street, about 100' .

[skillz]

What's making the GFS predict a NE shift after making landfall somehwere near Fort Meyers??? ...