ATL: SALLY - Post-Tropical - Discussion

[edu2703]

 https://twitter.com/NHC_Atlantic/status/1304442908498513921

[sma10]

I think this should be designated as a potential tropical cyclone at 5pm. It’s looking pretty decent and will be impacting land very soon.

It's already impacting land

[jlauderdal]

https://twitter.com/NHC_Atlantic/status/1304442908498513921

already an overperformer..we had one of these over labor a few years ago...wasnt supposed to do much and came through on labor day and was vigorous

[chaser1]

I think this should be designated as a potential tropical cyclone at 5pm. It’s looking pretty decent and will be impacting land very soon.

If trending convective activity and overall consolidation were to continue throughout the day, then a PTC seems entirely realistic - even likely. One reason is that we are at the cusp of the weekend and waiting until 11:00pm would somewhat defeat the purpose. Perhaps NHC might go as late as issuing a special advisory around 8:00-9:00pm? I guess it really comes down to what the maximum threat potential to S. Florida or offshore waters would be. If 96L were to begin to deepen and have a bit of a delayed approach to S. Fla or Keys, TD winds could pose a greater risk to boaters. Not sure if TD winds would have much of a threat to land areas but bands of moderate squalls with heavy rainfall could pose an increased risk of localized flooding throughout S. Florida. Then, there's always the risk of weak tornadic spin-ups as well.

[chaser1]

Just saw the Special advisory by NHC. Boy, this escalated a bit during the past 12 hours. Keep watching for dropping pressures.

[p1nheadlarry]

May also strengthen if tracks over everglades - ala Katrina

People always say this, but Katrina weakened over Florida. From the NHC report:

Code: Select all

Surface observations and velocity estimates from the Miami and Key West Doppler radars indicated that Katrina weakened over mainland Monroe County to a tropical storm with maximum sustained winds of 60 knots.

The thing about Katrina is that it only spent 6 hours over land because it moved WSW, so it never got much of a chance to weaken. But it didn't strengthen over land.

People seem to overestimate the brown ocean effect; there is increased friction over land and will not have the same enthalpy exchanges you see in the air-ocean pbl. Only storm I know that reached its maximum intensity over land in SFL was Andrew but it also weakened over land. The OK storm (Erin?) in 2007 probably had large-scale forcing to aide in its revival, but I'm not 100% on that.

[chaser1]

It’s got another 15-18hrs before FL. We shall see

See? That's what I had originally thought (and still do). Seemed as if NHC and the local NWS have been talking about 96L moving over S. Florida today and into this evening? I don't see this moving quite that fast. Looking at it now, i'd also guess somewhere closer to 15-24 hr.s. That would offer ample time for a T.D. (or even a weak T.S.) to develop right over the Florida Keys or extreme S. Florida on it's approach.

[Frank P]

Looking like quite a healthy tropical wave on the latest vis sat image

https://imgur.com/a/MD72uoo

[NDG]

I am going with there being a meso vort under that deep convection SSE of Nassau that will eventually become the LLC throughout the day.. under the MLC as well. the radar site is on nassau and we are not looking very far up.

Chances are quickly increasing..

https://i.ibb.co/4Y2kPXn/9999.gif

I also noticed the weak surface circulation/vorticity near Andros Island has not moved at all this morning, will definitely realign with the MLC as the day goes by.

[aspen]

I think this should be designated as a potential tropical cyclone at 5pm. It’s looking pretty decent and will be impacting land very soon.

It's already impacting land

I should’ve specified it’ll be impacting the CONUS very soon.

[Frank P]

Special tropical system update for s fl just posted by NHC
Updated:
Shower and thunderstorm activity located over the
northwestern and central Bahamas and the adjacent waters continues
to shows signs of organization. In addition, surface observations
indicate that pressures have fallen over the area since yesterday
and, along with wind data, suggest that a broad area of low pressure
could be forming between the northwestern Bahamas and South Florida.
This system is forecast to move westward at about 10 mph, crossing
the Bahamas and Florida today and tonight and moving into the
eastern Gulf of Mexico on Saturday. The disturbance could become a
tropical depression while it is near South Florida tonight, but it
is more likely to become a tropical depression while it moves slowly
west-northwestward over the eastern Gulf of Mexico this weekend and
early next week. Regardless of development, this system is expected
to produce locally heavy rainfall over portions of the Bahamas,
South Florida, and the Florida Keys during the next couple of days,
and interests there, as well as along the northern and eastern Gulf
coast, should monitor its progress.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 5 days...high...70 percent.

[Hypercane_Kyle]

JMO, 60/70% might be a tad low. I think this could become Sally before FL landfall.

[tropicwatch]

If it keeps this up, I am thinking PTC sometime today.

[TheStormExpert]

I smell the models failing once again with this.

[TallahasseeMan]

Is it safe to assume that NHC won't send recon into this thing until it gets into the gulf?

[Stormcenter]

It’s not a good smell either.

I smell the models failing once again with this.

[NDG]

I smell the models failing once again with this.

Especially the ICON considering how aggressive it usually is, it continues with no development at all on its latest 12z run.

[NDG]

Is it safe to assume that NHC won't send recon into this thing until it gets into the gulf?

Not scheduled until early afternoon tomorrow in the GOM.

[SFLcane]

Plenty of time to tighten up I could see a 50 mph ts before FL. What better place like the Gulf Stream in the Bahamas

[NDG]

I'm beginning to see SW winds starting to flow into 96L over central FL, little by little a larger surface circulation is starting to get going.