ATL: FLORENCE - Post-Tropical - Discussion

[tolakram]

Reminder, we do have a new shiny Discord chat room, S2K Chat Room Invite. Let me know your S2K name and if you're a pro met or an orange name so I can get you in the right groups.

[Aric Dunn]

Until Florence makes a definitive turn to the WSW/SW and the data from the Gulfstream comes in, I'm just going to remind everyone not to become complacent as major hurricanes have hit the Northeast also during this time period, aka, the Long Island Express:

the WSW motion is very real and definitive no need to wait on that and that is just DVORK which has been a little to far north

[SSL]

Flo continues WSW at a decent clip... 00z models should be faster than 18z...

Interestingly, I think the models that have been going farther south have been going slower (UKMET, I'm looking at you)

[SFLcane]

Aric it’s been dipping most of today hopefully this does not have implications later

[Aric Dunn]

Aric it’s been dipping most of today hopefully this does not have implications later

If it makes it to 24N or below you can probably count on it.

[Kazmit]

It seems like the path of this storm is going to keep on shifting further and further south. Will probably plow into South America if this keeps up.

[SFLcane]

Aric were exactly do you have it I’ve got around 24.5

[Blown Away]

Aric it’s been dipping most of today hopefully this does not have implications later

If it makes it to 24N or below you can probably count on it.

In addition Flo has been moving faster than NHC... I think the 00z models may trend farther S due to these initial SW adjustments and Flo moving faster than expected...

[johngaltfla]

I'm going to wait until Kermit reports so Sunday will be the "ruh-roh" day. That's why I'm going to be patient until the recon gets there.

[Hurricaneman]

Aric were exactly do you have it I’ve got around 24.5

I have it at 24.25 but not much difference really

[Aric Dunn]

Aric were exactly do you have it I’ve got around 24.5

it is difficult to see since it has been covered again by high clouds. but if you look closely you can see it clearly just before the high clouds cover it. looks like 24.4N maybe less.

[Blinhart]

So is there a possibility of this crossing over the peninsula of Florida and entering the GoM?

[hurricaneCW]

I'm not seeing any substantial sw dive. She's moving quite slowly and I think any short term dips will have negligible effects in the long run.

It'll really come down to how strong the ridge becomes early next week.

[Blinhart]

I'm not seeing any substantial sw dive. She's moving quite slowly and I think any short term dips will have negligible effects in the long run.

It'll really come down to how strong the ridge becomes early next week.

I don't understand what you are seeing, everyone else (including me) see the SW dive at a good clip.

[Hurricaneman]

So is there a possibility of this crossing over the peninsula of Florida and entering the GoM?

A small one like 10% as of now from 2% earlier in the day but we here in Florida also need to keep monitoring this, I have a feeling the upper air missions will hold the key

[Hurricaneman]

I'm not seeing any substantial sw dive. She's moving quite slowly and I think any short term dips will have negligible effects in the long run.

It'll really come down to how strong the ridge becomes early next week.

I don't understand what you are seeing, everyone else (including me) see the SW dive at a good clip.

What you may be seeing is the MLC moving SW towards the LLC but there is still some south of west movement of the LLC but that is slowly flattening out to a more west movement

[Nimbus]

If you look at 60 frames of the water vapor loop zoomed out, it looks like just a very slow WWSW drift.
Still a long way from the CONUS and plenty of time for a weakness in the ridge to show up, but it is concerning that so many models are currently forecasting a landfall.

[cycloneye]

Tropical Storm Florence Discussion Number 35
NWS National Hurricane Center Miami FL AL062018
1100 PM AST Fri Sep 07 2018

Florence remains a sheared tropical cyclone. Satellite images
indicate that the low-level center is partially exposed on the
southwesterly edge of a large convective mass, with the overall
circulation somewhat elongated from southwest to northeast.
A blend of the latest Dvorak wind speed estimates from TAFB/SAB and
the CIMSS SATCON gives a value of 50 kt for this advisory.

While the winds at 200 mb are already from an easterly direction
near the center of Florence, there is significant shear from
northwesterly winds from 300-500 mb, undercutting the outflow layer.
This shear is forecast to relax by the global models over the next
36 hours as an anticyclone builds to the north of the storm, which
should promote some strengthening by Sunday. After 48 hours, the
deep-layer flow becomes easterly near the cyclone, with very little
shear while the system is over very warm waters. This pattern
favors significant intensification, and most of the guidance brings
Florence back to a category 4 hurricane in 4 or 5 days. The
intensity forecast is very similar to the last one, and is raised
slightly at days 3 and 4 to come into better agreement with the
guidance. It is interesting to note that even with a lower initial
intensity, the guidance is higher than the last cycle, which speaks
to the strength of the signal for intensification in the long range.

The initial motion estimate is 265 degrees at 6 kt. Florence is
expected to continue moving slowly westward for the next 48 hours
under the influence of a weak mid-level ridge over the western
Atlantic. By days 4 and 5, an exceptionally strong blocking ridge
is forecast to develop between Bermuda and the Northeast U.S. and
build westward, keeping Florence on a west-northwestward trajectory
with a notable increase in forward speed by the end of the forecast
period. It feels like a broken record to mention that the overall
guidance envelope keeps shifting southwestward, and the official
forecast is moved in that direction. Unfortunately with such a
large well-defined steering current from the ridge becoming likely,
the extended-range risk to the United States keeps rising, which is
confirmed by the majority of the latest ensemble guidance.

Key Messages:

1. Regardless of Florence's eventual track, large swells are
affecting Bermuda and will begin to affect portions of the U.S.
East Coast this weekend, resulting in life-threatening surf and rip
currents.

2. The risk of other direct impacts associated with Florence along
the U.S. East Coast next week has increased. However, there is
still very large uncertainty in model forecasts of Florence's track
beyond day 5, making it too soon to determine the exact location,
magnitude, and timing of these impacts. Interests near and along
the U.S. East Coast should monitor the progress of Florence through
the weekend and ensure they have their hurricane plans in place.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0300Z 24.8N 53.2W 50 KT 60 MPH
12H 08/1200Z 24.7N 54.1W 50 KT 60 MPH
24H 09/0000Z 24.7N 55.2W 55 KT 65 MPH
36H 09/1200Z 24.7N 56.3W 60 KT 70 MPH
48H 10/0000Z 25.0N 57.8W 70 KT 80 MPH
72H 11/0000Z 25.8N 62.3W 95 KT 110 MPH
96H 12/0000Z 27.5N 68.5W 115 KT 130 MPH
120H 13/0000Z 30.5N 74.5W 115 KT 130 MPH

$$
Forecaster Blake

[HurricaneEric]

Tweet from @CraigSetzer:

“Little quick thought.... wouldn't be surprised to see some SOUTH of WEST motion next 24 hours as Florence gets through the ridge extension. Unknown what downstream track impacts that would create. Little southward model shift near US? Hard to tell.”




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[Blown Away]

11pm Disco: Still very large track uncertainty after day 5...