ATL: IDA - Models

[Steve]

Nam shows pressure at 896… omg if that ever happens

I forgot to mention that it’s also good for laughter.

[IcyTundra]

0Z ICON is further west.

[AxaltaRacing24]

00z Guidance.


https://i.imgur.com/iLSVVJJ.png

My thinking is for this to be more like a low to mid end cat2 by landfall. I wouldn't be shocked if it got stronger but chances are it won't be a cat4 or 5.

Yeah, I think 4 or 5 are unlikely as well if not impossible. Earlier I guessed 70% at Cat 3. Not sure I'm that high anymore - probably more like 40-45%. But since they sample so much stuff now, they may be able to find at least an extended gust into Cat 3 territory over the Gulf. Glad to see an extreme slowdown is probably off the table too. I'm a wuss and not really ready to make a call like I have for the last 25 years on here or CFHC. But I feel like it will landfall between Slidell and Marsh Island with the zoomed in range of Cocodrie to Centerville/Patterson (just west of Morgan City).

Are we sure that a 4 is impossible? Grace nearly did it in 24 hours, and the models had higher pressure estimates at landfall than with Ida. Also, even the ICON shows 963...

[catskillfire51]

NHC adjusted their cone to the west initially as well, instead of going to the east of Grand Cayman it is now going over Grand Cayman.

[IcyTundra]

0Z ICON landfall is near the Rockefeller Wildlife Refuge east of Grand Chenier 962 MB. Lafayette would get hammered by the NE eyewall if this happened.

[Keldeo1997]

ICON coming in West and much stronger

[ThetaE]

I've seen lots of posts about the NAM today! Definitely a model you should not listen to for TCs. But I don't know if people are really aware of what causes the model to break.

Hurricanes' high winds extract energy from the oceans through evaporation/"heat fluxes," but those high winds also upwell colder waters up to the surface in a self-limiting fashion. The NAM is a regional model that's mostly just simulating weather over land, so having to also model ocean dynamics is an extra complication that in most situations doesn't make sense in terms of computational costs. So the NAM just... takes the SSTs at hour 0 and never changes them. As a result, hurricanes extract WAY more energy than should be physically possible.

Otherwise, in my experience it's a great model for severe and winter weather. And it would handle troughs/ridges well, but TC tracks are very intensity dependent so you really shouldn't trust anything about what it shows.

[skyline385]

Nam shows pressure at 896… omg if that ever happens

Burg's recent tweet is very relevant to this thread, please stop everyone

https://twitter.com/burgwx/status/1430997712380391425

[skyline385]

0Z ICON moves away from NOLA as well, and you know its going to be intense when even ICON has it deepening to 962mb before landfall.

[ThetaE]

Nam shows pressure at 896… omg if that ever happens

Burg's recent tweet is very relevant to this thread, please stop everyone

https://twitter.com/burgwx/status/1430997712380391425

Ah, I didn't know about the model allowing latent heat fluxes at high RH. That plus the fixed SST problem I mentioned spells disaster for properly modeling surface heat exchanges in TCs. Alicia Bentley is a great source for learning about the nitty-gritty of what makes weather models tick.

[psyclone]

My thinking is for this to be more like a low to mid end cat2 by landfall. I wouldn't be shocked if it got stronger but chances are it won't be a cat4 or 5.

Yeah, I think 4 or 5 are unlikely as well if not impossible. Earlier I guessed 70% at Cat 3. Not sure I'm that high anymore - probably more like 40-45%. But since they sample so much stuff now, they may be able to find at least an extended gust into Cat 3 territory over the Gulf. Glad to see an extreme slowdown is probably off the table too. I'm a wuss and not really ready to make a call like I have for the last 25 years on here or CFHC. But I feel like it will landfall between Slidell and Marsh Island with the zoomed in range of Cocodrie to Centerville/Patterson (just west of Morgan City).

Are we sure that a 4 is impossible? Grace nearly did it in 24 hours, and the models had higher pressure estimates at landfall than with Ida. Also, even the ICON shows 963...

It's probably more pragmatic to focus on a reasonable range (probabilities) instead of high end possibilities. that's how i always try to think. to that end the system is far more likely to end up a 2 or perhaps low end 3 rather than a 4 or a 5. these sorts of details are impossible to resolve at this point and a more sensible solution may not be to talk about some extreme event and instead focus on just how bad a 90-100kt cane can be. That, over one's neighborhood is an extreme event. 8-12" rain, 7-11' surge, triple digit wind gusts, far flung tornadoes... I'd bet on a 90-100kt storm at this point. and that's bad. really bad. For some historical reference, Camille crossed western Cuba as a 100kt cat 3... so it was already a major as it entered the gulf. Of course i know about Michael but for every memorable exceptional event like that there are many others that came up short of that...but were still bad and warrant respect and preparation.

[cycloneye]

0Z ICON moves away from NOLA as well, and you know its going to be intense when even ICON has it deepening to 962mb before landfall.

https://i.imgur.com/dMcjAjG.png

Lower pressure than the 18z run.

[ElectricStorm]

0z GFS 993mb over W Cuba so far

[IcyTundra]

00Z GFS looks like it is going to be further west than the 18Z run.

[CrazyC83]

At 42 hours, 00Z GFS is about 0.6 degrees south of 18Z GFS.

[PTrackerLA]

Huge shift SW from 18z to 00z on GFS at 66hrs, stronger too

[ElectricStorm]

GFS peaks at 953, landfalls at 959

[IcyTundra]

00Z GFS goes right over Houma, LA.

[ElectricStorm]

GFS has it deepening at about 1mb/hour in the gulf, and gets it to 953. Any brief period of faster intensification could get it to Cat 4 a similar scenario to this run plays out. Yeah it's not looking good

[Blinhart]

So will this be one of those storms that have West bias models at night and East bias models during the day, so got to go with the middle of the 2?