ATL: FLORENCE - Post-Tropical - Discussion

[plasticup]

Convection has completely covered the center of circulation. She's ready for takeoff.

[Hurricane Andrew]

So a question for the pro-mets here: the "pulsing" convection seen for the last 2-3 hours over the general area of the center, that will help to "push out" the dry air from the circulation, correct?

[WAcyclone]

Another very interesting graphic by Sam Lillo:

 https://twitter.com/splillo/status/1038521486867398662

[supercane4867]

Another very interesting graphic by Sam Lillo:

https://twitter.com/splillo/status/1038521486867398662

And 6 of those 7 storm did peak as 125kt or stronger. Isidore was the only one because it unexpectedly went into Yucatan.

[GCANE]

Three overshooting tops firing in the last 45 minutes

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

[Hurricane Andrew]

And 6 of those 7 storm did peak as 125kt or stronger. Isidore was the only one because it unexpectedly went into Yucatan.

NHC are very, very good at their job...if they say 125kt, I'm inclined to listen.

[NotoSans]

Up to 60kt as per latest advisory.

[TheDreamTraveler]

Three overshooting tops firing in the last 45 minutes

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

Yeah, Florence is going to really get going very soon. Once it gets out of the shear the chance of rapid intensification is very high.

[pgoss11]

State of Emergency just declared in South Carolina.

[sunnyday]

What would more ridging cause to happen to Florence’s path?

[TheDreamTraveler]

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

[lando]

Pretty interesting that SHIPS is now predicting Florence will struggle more with dry air, perhaps inhibiting it’s northernly component. Nhc disregards it at moment but mentions it still

[Hurricane Andrew]

Pretty interesting that SHIPS is now predicting Florence will struggle more with dry air, perhaps inhibiting it’s northernly component. Nhc disregards it at moment but mentions it still

Eh...I compared to 06z SHIPS, and it's about the same. Plus, if you scroll down to where each factor effects the intensity output, it seems to merely serve as a "limiter" (maxes out at +3, min at 0) than a "weakener". SHIPS still progs this to go major.

[Spacecoast]

Big picture. I would say more active season than I was anticipating, this is just the Atlantic.

[Ken711]

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

[bg1]

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

The NAM (yeah, I know) showed stronger ridging and a more westward path on 18z.

[toad strangler]

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

Way too 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.

[floridasun78]

Big picture. I would say more active season than I was anticipating, this is just the Atlantic.
https://image.ibb.co/gx6bZp/9812speg.jpg

what site this from?

[hurricaneCW]

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.

[psyclone]

Such a scary endpoint on that 5 day forecast.... a major hurricane quickly running out of ocean...