ATL: FLORENCE - Post-Tropical - Discussion

[KyleEverett]

Reminder, if you quote someone who posted a picture, please delete the tags so you don't fill up the thread with duplicate images and increasing bandwidth usage.

Florence will struggle to develop for the next 2 days, once the ridge builds overhead and she gets moving, then she'll likely ramp up quickly.

Models will likely start correcting their tracks as well. We forget that she's barely been moving over the past 2 days.

She won't struggle. Forecast has steady strengthening over the next 2 days as she heads westward. Will be a 90 mph storm by 48H.

[NC George]

Officially 'In The Cone.'

[otowntiger]

So is this the end of south and west model runs based on the 12Z?

Way to far out to determine that model shifts are done. NHC specifically mentions NORTH FL through NC as the region that should be preparing NOW. That's a pretty big spread. More changes to come for sure. Within that scope.

I’m pretty sure that major shifts are done. I believe that the cone is pretty much what it will be. NHC is really good with track 5 days and less. Carolina hit- north or south or both.

[Bocadude85]

It’s interesting that the NHC specifically mentions the 12Z HWRF run..obviously it has some weight given to it...a lot of people on here seemed to be discrediting it earlier.

[toad strangler]

So is this the end of south and west model runs based on the 12Z?

Way to far out to determine that model shifts are done. NHC specifically mentions NORTH FL through NC as the region that should be preparing NOW. That's a pretty big spread. More changes to come for sure. Within that scope.

I’m pretty sure that major shifts are done. I believe that the cone is pretty much what it will be. NHC is really good with track 5 days and less. Carolina hit- north or south or both.

That's fair, BUT, the NHC specifically mentioned N FL through NC. Not me.

[Spacecoast]

floridasun: "what site this from?"
NOAA HFIP (Hurricane Forecast Improvement Program)

Way to far out to determine that model shifts are done. NHC specifically mentions NORTH FL through NC as the region that should be preparing NOW. That's a pretty big spread. More changes to come for sure. Within that scope.

I’m pretty sure that major shifts are done. I believe that the cone is pretty much what it will be. NHC is really good with track 5 days and less. Carolina hit- north or south or both.

That's fair, BUT, the NHC specifically mentioned N FL trough NC. Not me.

The 5-day end of the cone is a little misleading. Until the 2pm Thur M dot is actually at land fall, it could still encompass extreme NE Fl, right? Accuracy does not improve toward the big end of the cone, it is just the 5th day 'circle'.

[cycloneye]

Tropical Storm Florence Discussion Number 38
NWS National Hurricane Center Miami FL AL062018
500 PM AST Sat Sep 08 2018

A NOAA P3 aircraft conducted a research mission several hours ago
in Florence and measured SFMR surface winds of around 60 kt and
winds up to 65 kt at a flight level of 8000 feet. Velocities of
65-70 kt at 500 meters were also measured by the Doppler radar on
the plane. Based on these data, the initial wind speed is raised to
60 kt. Dropsonde data also showed that the central pressure was
down to 989 mb.

Florence is slowly recovering from the dry air its circulation
ingested while it was under the influence of strong shear.
Convection in the outer bands is relatively thin but is deeper and
more persistent near the center. Now that the shear has decreased
and the warm waters ahead of Florence reach deeper into the ocean,
continued strengthening is anticipated. In fact, the official
forecast continues to show a period of rapid intensification, now
beginning 12-24 hours, with Florence reaching major hurricane
intensity between 36-48 hours. One fly in the ointment is that the
SHIPS diagnostics are keeping mid-level relative humidities around
the cyclone around 50 percent, which isn't particularly moist, but
I'm going to assume that Florence will be able to scour out the dry
air within its circulation in the coming days. The HCCA model and
the ICON intensity consensus support maintaining a forecast peak
intensity of 125 kt in 4 days or so, so no significant changes were
made from the previous forecast. Regardless of the specifics of
the other models--some of which are higher and some of which are
lower--Florence is expected to be a powerful major hurricane on
days 3 through 5 as it moves across the southwestern Atlantic Ocean.

Florence is creeping westward (270 degrees) at 4 kt, trapped
between high pressure to its northeast and southwest. A different
blocking ridge is expected to develop north and northeast of
Bermuda over the next few days, causing Florence to accelerate
toward the west-northwest and northwest between days 3-5. There
have been some notable shifts in the model guidance on this cycle,
with the ECMWF model swinging to the northeast closer to the GFS,
and the HWRF model swinging farther south along the southern edge
of the guidance envelope. Despite this change in the deterministic
ECMWF run, its individual ensemble members are still showing a
significant spread of solutions from just north of the Bahamas to
offshore the coast of North Carolina by day 5. Because of this
spread, the updated NHC track forecast largely maintains
continuity and remains close to the TVCN multi-model consensus.
And despite the ECMWF's shift, this track prediction remains north
of the HCCA and FSSE solutions.

Key Messages:

1. Florence is forecast to be a dangerous major hurricane near the
southeast U.S. coast by late next week, and the risk of direct
impacts continues to increase. However, given the uncertainty in
track and intensity forecasts at those time ranges, it's too soon to
determine the exact timing, location, and magnitude of those
impacts.

2. Interests along the U.S. East Coast, particularly from north
Florida through North Carolina, should closely monitor the progress
of Florence, ensure they have their hurricane plan in place, and
follow any advice given by local officials.

3. Large swells affecting Bermuda and portions of the U.S. East
Coast will continue into next week. These swells will result in
life-threatening surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 24.6N 54.7W 60 KT 70 MPH
12H 09/0600Z 24.6N 55.4W 70 KT 80 MPH
24H 09/1800Z 24.7N 56.6W 80 KT 90 MPH
36H 10/0600Z 25.0N 58.3W 95 KT 110 MPH
48H 10/1800Z 25.4N 60.5W 110 KT 125 MPH
72H 11/1800Z 26.9N 66.4W 120 KT 140 MPH
96H 12/1800Z 29.5N 72.5W 125 KT 145 MPH
120H 13/1800Z 32.5N 77.0W 120 KT 140 MPH

$$
Forecaster Berg

[cycloneye]

Tropical Storm Helene Discussion Number 6
NWS National Hurricane Center Miami FL AL082018
500 PM AST Sat Sep 08 2018

During the past few hours, Helene has developed a convective band
that wraps about three-quarters of the way around the storm, and
the intensity of the inner core convection has increased. In
addition, microwave imagery shows an elliptical inner ring feature.
Satellite intensity estimates at 18Z were in the 35-50 kt range, and
given the recent increase in organization the initial intensity is
increased to 50 kt.

Helene should continue to strengthen through at least 72 h in a
light vertical shear environment over sea surface temperatures near
27C. This part of the intensity forecast has been increased over
the previous forecast and lies near the intensity consensus.
However, there remain a couple of alternate forecast scenarios. The
first is that Helene could rapidly intensify and become stronger
than currently forecast, and the rapid intensification index of the
SHIPS model has about a 35 percent chance of 25 kt of strengthening
in the next 24 h. The second is that a large plume of African dust
and associated dry air that has spread over the Cabo Verde Islands
starts entraining into the cyclone and inhibits intensification.
The former alternative is more likely than the latter at this time.
After 72 h, Helene is expected to encounter increasing southwesterly
shear associated with a mid- to upper-level trough over the central
Atlantic, which should cause the system to weaken significantly.

The initial motion is 275/11. There again is little change in the
forecast guidance or the forecast track, with Helene expected to
move westward to west-northwestward for the next 3 days or so on the
south side of the subtropical ridge, then turn northwestward in
response to the aforementioned trough.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 13.6N 21.7W 50 KT 60 MPH
12H 09/0600Z 13.7N 23.5W 55 KT 65 MPH
24H 09/1800Z 14.1N 26.2W 65 KT 75 MPH
36H 10/0600Z 14.7N 29.1W 75 KT 85 MPH
48H 10/1800Z 15.5N 32.0W 85 KT 100 MPH
72H 11/1800Z 17.5N 37.0W 85 KT 100 MPH
96H 12/1800Z 19.5N 40.5W 65 KT 75 MPH
120H 13/1800Z 23.0N 42.5W 55 KT 65 MPH

$$
Forecaster Beven

[Hurricane Andrew]

Tropical Storm Helene Discussion Number 6
NWS National Hurricane Center Miami FL AL082018
500 PM AST Sat Sep 08 2018

During the past few hours, Helene has developed a convective band
that wraps about three-quarters of the way around the storm, and
the intensity of the inner core convection has increased. In
addition, microwave imagery shows an elliptical inner ring feature.
Satellite intensity estimates at 18Z were in the 35-50 kt range, and
given the recent increase in organization the initial intensity is
increased to 50 kt.

Helene should continue to strengthen through at least 72 h in a
light vertical shear environment over sea surface temperatures near
27C. This part of the intensity forecast has been increased over
the previous forecast and lies near the intensity consensus.
However, there remain a couple of alternate forecast scenarios. The
first is that Helene could rapidly intensify and become stronger
than currently forecast, and the rapid intensification index of the
SHIPS model has about a 35 percent chance of 25 kt of strengthening
in the next 24 h. The second is that a large plume of African dust
and associated dry air that has spread over the Cabo Verde Islands
starts entraining into the cyclone and inhibits intensification.
The former alternative is more likely than the latter at this time.
After 72 h, Helene is expected to encounter increasing southwesterly
shear associated with a mid- to upper-level trough over the central
Atlantic, which should cause the system to weaken significantly.

The initial motion is 275/11. There again is little change in the
forecast guidance or the forecast track, with Helene expected to
move westward to west-northwestward for the next 3 days or so on the
south side of the subtropical ridge, then turn northwestward in
response to the aforementioned trough.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 13.6N 21.7W 50 KT 60 MPH
12H 09/0600Z 13.7N 23.5W 55 KT 65 MPH
24H 09/1800Z 14.1N 26.2W 65 KT 75 MPH
36H 10/0600Z 14.7N 29.1W 75 KT 85 MPH
48H 10/1800Z 15.5N 32.0W 85 KT 100 MPH
72H 11/1800Z 17.5N 37.0W 85 KT 100 MPH
96H 12/1800Z 19.5N 40.5W 65 KT 75 MPH
120H 13/1800Z 23.0N 42.5W 55 KT 65 MPH

$$
Forecaster Beven

Wrong thread, bud

[TheDreamTraveler]

If you go look here at this satellite near the end you can see a very top part of Florences clouds getting sucked up by the trough. It's very slight. I still can't believe how close this was to getting sent out to sea. I don't think it's actually impacting her movement. It's near the end of the loop.

http://weather.cod.edu/satrad/exper/?pa ... =undefined

[ScottNAtlanta]

If you goes look here at this satellite near the end you can see a very top part of Florences clouds getting sucked up by the trough. It's very slight. I still can't believe how close this was to getting sent out to sea. I don't think it's actually impacting her movement. It's near the end of the loop.

http://weather.cod.edu/satrad/exper/?pa ... =undefined

What you are seeing is the outflow becoming established. The clouds going into the weakness were the ones blown off while the storm was sheared. They really are not related to anything going on now. 96 frames is a long time, plus there is a southward component going on the entire loop.

[Three Blind Mice]

Wrightsville Beach High Tide for Thursday night is 11:13pm 4.6' feet, next high tide is Friday at 11;46am 5.1' feet

[cheezyWXguy]

I know we are a long ways out, and discussing an actual landfall location at this point is nothing more than speculation, but one thing that concerns me is Florence's storm surge potential, given not only its potential increase in strength, but size as well.

Are the Carolinas fairly vulnerable to storm surge, or is it more like the east cost of Florida with a sharp continental shelf that tends to mitigate surge effects?

[jdjaguar]

If I lived in the Atlantic Beach/Morehead City/Ocracoke area, I would be boarding up
And bugging out.

[ScottNAtlanta]

I know we are a long ways out, and discussing an actual landfall location at this point is nothing more than speculation, but one thing that concerns me is Florence's storm surge potential, given not only its potential increase in strength, but size as well.

Are the Carolinas fairly vulnerable to storm surge, or is it more like the east cost of Florida with a sharp continental shelf that tends to mitigate surge effects?

The surge is going to be dependent to a degree by angle of impact. If it goes in perpendicular to the coast you will have higher surge than if it sideswipes it. I would think the outer banks are susceptible to surge, but I dont live there.

[gatorcane]

So is this the end of south and west model runs based on the 12Z?

Way to far out to determine that model shifts are done. NHC specifically mentions NORTH FL through NC as the region that should be preparing NOW. That's a pretty big spread. More changes to come for sure. Within that scope.

I’m pretty sure that major shifts are done. I believe that the cone is pretty much what it will be. NHC is really good with track 5 days and less. Carolina hit- north or south or both.

Agreed looks like a Carolina hit or just offshore. FLORIDA particularly central and south look to be in the clear. Still not all clear for north Florida yet.

[HurricaneBelle]

If either the latest GFS or Euro verifies, rainfall is going to be measured on a scale from Harvey to Noah's Ark.

[TheDreamTraveler]

 https://twitter.com/TropicalTidbits/status/1038501180580798464

[LCfromFL]

First, let me say that you should ALWAYS listen to local officials when it comes to evacuating. Now having said that, this surge map may be helpful in visualizing the impact of surge in your area. I live nearly 25 miles - yes miles -inland and we could be affected by storm surge. Worst case scenario for a Cat 5 would have more than 9 FEET of surge. Hide from the wind. Run from the water. Be safe.

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

[chaser1]

Wrightsville Beach High Tide for Thursday night is 11:13pm 4.6' feet, next high tide is Friday at 11;46am 5.1' feet

Question: Do you recall which was the last storm to fairly directly strike Wrightsville Beach?