ATL: SALLY - Post-Tropical - Discussion

[hurricaneCW]

Shear is rapidly dropping right now and I expect significant consolidation today. It could even become a hurricane by Sunday night.

A major hurricane is definitely possible given the forecast conditions however the very slow movement near and after landfall is most concerning. The impacts will be devastating whether it's a Cat 1 or 3.

[SohCahToa]

Woke up to weather alerts for the new advisory. Headed to Lowe’s here on the northshore as they open to grab a generator and some extra supplies. Riding out my first storm as a homeowner. I’ve had a bad feeling but didn’t want to overreact, but it’s time finalize the prep.

[GCANE]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

[eastcoastFL]

Reminds me a bit of the small inner core Gordon in 2018 developed as it was moving away from Florida. I'm hoping that the same result occurs.

https://twitter.com/pppapin/status/1305045241272164352?s=21

I was looking at the archived thread for 2018's TS Gordon, which had a very similar small core and similar track earlier in Sept with very similar E GOM SSTs near 30C. Like for this storm, there was a pretty good bit of talk about the possibility of RI and most folks expected a H hitting the Gulf coast. The NHC peak strength was projected to be 75 mph offshore before weakening some vs 85 for this one. The peak ended up being 70 mph starting 130 miles from the Gulf coast and lasting til landfall.

Gordon archived thread:
viewtopic.php?f=88&t=119828&start=600


Gordon track:
https://i.imgur.com/eTEXPAQ.png

How does Sally compare to Gordon? Any thoughts?

Do you recall what the conditions were like for Gordon? Was there any shear or dry air present in the gulf at the time?

[eastcoastFL]

[eastcoastFL]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

What do you think the potential intensity looks like? What could keep her from ramping up here?

[eastcoastFL]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

GCane- Another question I meant to ask is how much do you think she can expand? She’s rather small now but still a young system. Cloud cover appears to be expanding with increasing convection this morning. Do you foresee her staying a rather tiny system?

[USTropics]

If you live on the coast, especially in an area susceptible to storm surge, please pay attention to the latest forecast discussion wording:

1. An extremely dangerous and life-threatening storm surge is now
expected, and a Storm Surge Warning is in effect for areas outside
the southeastern Louisiana Hurricane and Storm Damage Risk Reduction
System from Port Fourchon Louisiana to the Mississippi/Alabama
border. Residents in these areas should follow any advice given by
local officials.

Here is a storm surge map for a category 1 storm:


Surge significantly increases when we reach up to a category 2 storm:


The current forecast is calling for a category 2 hurricane, but an even stronger system can't be completely ruled out. Storm surge with a category 3 storm is extremely dangerous:


Scale:


Src - http://noaa.maps.arcgis.com/apps/MapSeries/index.html?appid=d9ed7904dbec441a9c4dd7b277935fad&entry=1

[GCANE]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

What do you think the potential intensity looks like? What could keep her from ramping up here?

Once the GA-coast ULL breaks, I don't see anything to hold her back.
Enough time in the water and I would say better than 50/50, a major at landfall.

What's your thoughts?

[PavelGaborik10]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

GCane- Another question I meant to ask is how much do you think she can expand? She’s rather small now but still a young system. Cloud cover appears to be expanding with increasing convection this morning. Do you foresee her staying a rather tiny system?

https://cdn.star.nesdis.noaa.gov/GOES16/ABI/SECTOR/GM/AirMass/GOES16-GM-AirMass-1000x1000.gif?hash=2497

Her northern side has been brutally impacted by shear and is now finally beginning to fill in. I think she'll be a medium sized system but that's more of a guess than anything. Shear is clearly relaxing towards her north and she's expanding with each frame.

It'll be interesting.

[PavelGaborik10]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

GCane- Another question I meant to ask is how much do you think she can expand? She’s rather small now but still a young system. Cloud cover appears to be expanding with increasing convection this morning. Do you foresee her staying a rather tiny system?

https://cdn.star.nesdis.noaa.gov/GOES16/ABI/SECTOR/GM/AirMass/GOES16-GM-AirMass-1000x1000.gif?hash=2497

Her northern side has been brutally impacted by shear and is now finally beginning to fill in. I think she'll be a medium sized system but that's more of a guess than anything. Shear is clearly relaxing towards her north and she's expanding with each frame.

It'll be interesting.

[GCANE]

The last inhibiting factor, the ULL over the GA coast, is being taken out by convection.
That'll open the door for a perfect poleward outflow channel.
Already have the ULL off the TX/M border to kick in an equatorward outflow channel.
Sunday afternoon may be even more hairy than what I was expecting.

https://i.imgur.com/zpZJ1YR.png

GCane- Another question I meant to ask is how much do you think she can expand? She’s rather small now but still a young system. Cloud cover appears to be expanding with increasing convection this morning. Do you foresee her staying a rather tiny system?

https://cdn.star.nesdis.noaa.gov/GOES16/ABI/SECTOR/GM/AirMass/GOES16-GM-AirMass-1000x1000.gif?hash=2497

Radar shows she is already big.
Very low chance she'll be a pinhole.
I expect this afternoon the outflow will look ideal.
She'll be running with a full head of steam (lots of momentum).
The infeed looks really good. Its very unusual to see such a good infeed on low-level water vapor imagery.

[Nimbus]

NHC forecast intensity was being held above model consensus closer to the Sunday afternoon stacked solutions.
This morning shear goes poof so 18Z GFS won't verify.
Everybody in the cone is preparing for a hurricane which is all we can do.

[GCANE]

Here's the chronic high-CAPE pool I always talk about that sits SE of Houston.
When Sally gets to the NE of that, she'll start drinking in all that unstable air.
That's when things should start getting really intense.

[PavelGaborik10]

Going to be an interesting one folks. We have a tropical system entertaining the GOM at the climatology peak of hurricane season.

This is the type of scenario that very well may determine whether this season ends up in the 2005 echelon in terms of impacts towards the United States. It still has a plethora of time over water, so we'll see how the condition are.

My amateur guess would be a cat 1-2 at landfall.

Leaning strong 2, 110 MPH peak.

[eastcoastFL]

Nhc bumping max intensity up to Cat 2 100mph now. With her strengthening this morning they didn’t have much of a choice. She’s got an open highway of warm water and not much in the way.


Disco

While northwesterly shear has been affecting Sally, the global
models suggest that the shear will decrease later today as it moves
under a narrow ridge. Models all respond to these changing
conditions by showing intensification, but they disagree on the rate
of change. It is an extremely tricky forecast because of how this
might happen close to landfall, but guidance is generally 5-10 kt
higher than the last cycle so the intensity forecast has been raised
by those amounts up through landfall. It is worth noting that rapid
intensification is a possibility if the system develops a more solid
inner core on Monday, and stronger solutions like the HWRF model
can't be dismissed.

[eastcoastFL]

Here's the chronic high-CAPE pool I always talk about that sits SE of Houston.
When Sally gets to the NE of that, she'll start drinking in all that unstable air.
That's when things should start getting really intense.

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

Thanks G. Always value your input!

[tronbunny]

Just putting this out there in case anyone missed it.
From NHC 5am (EDT) Advisory

KEY MESSAGES:

1. An extremely dangerous and life-threatening storm surge is now
expected, and a Storm Surge Warning is in effect for areas outside
the southeastern Louisiana Hurricane and Storm Damage Risk Reduction
System from Port Fourchon Louisiana to the Mississippi/Alabama
border. Residents in these areas should follow any advice given by
local officials.

2. Hurricane conditions are expected by early Tuesday from Grand
Isle, Louisiana to Ocean Springs, Mississippi, including
Metropolitan New Orleans, with tropical storm conditions likely by
Monday. Preparations should be rushed to completion in those areas.

3. Tropical Storm Sally is expected to produce flash flooding across
southern and central Florida and prolong existing minor river
flooding across Central Florida through Monday. Significant flash
flooding and minor to isolated major river flooding is likely across
portions of the Central Gulf Coast from Monday through the middle of
the week.

[GCANE]

That whole ridging idea about the steering is being blown away by the Rossby wave.
On approach, the RW will be flattened out West to East.
500mb shows a push south, 700mb a push west.
This actually may skirt the coast for awhile.
Very hard to tell which way she'll go.

One thing that looks for certain is that she'll be under the ARWB.
Could be a good chance she may hit maximum potential intensity.

[GCANE]

Here's the chronic high-CAPE pool I always talk about that sits SE of Houston.
When Sally gets to the NE of that, she'll start drinking in all that unstable air.
That's when things should start getting really intense.

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

Thanks G. Always value your input!

My pleasure. I hope you are not effected by this.