ATL: FLORENCE - Post-Tropical - Discussion

[SSL]

So I had a thought earlier that I posted on the Wunderground blog... I wanted to throw it out here to you guys about Florence...

I wonder if the eyewall issues we've seen haven't been because of this dry air the whole time... Think about it.. If dry air has been closing off the southwest quadrant and pinching the eyewall in.. All that energy is converging in that northwest through southeast eyewall. Well what happens once it's through that? You enter an area of divergence as the eyewall energy is allowed to spread out, which might be why we've seen it hard for the northeastern eyewall to close off.... So by that definition, if that's what the issue that has been plaguing florence is.. Then I would expect to see a couple things as she closes out that dry air.. 1. The western eyewall will spread out and appear weaker. 2. The pressure may go up as the inner core stabilizes... But then 3, you'll see a much more circular and filled eyewall start to build and the pressure will then start dropping like a rock...

So what do you guys think?

[Audrey2Katrina]

MAX FL WIND 130 KT 052 / 20 NM 03:42:00Z

From vortex message over in recon thread. 150 mph flight level, or close to it.

True; but the SFMR estimated surface winds are about 123 mph inbound, and around 108 outbound... Granted that's SFMR estimates... and right now is no time to underplay the dangers involved.

[Bunkertor]

Stay safe, everybody !

[beoumont]

Can anyone recall any Atlantic hurricane BECOMING a category 5 north of latitude 28??

[Hammy]

Can anyone recall any Atlantic hurricane BECOMING a category 5 north of latitude 28??

I can't think of one that's existed at all at that latitude outside the Gulf. Doesn't look like it'll happen with Florence either if it keeps through ERCs so close together.

[Hurrilurker]

In the last few sat frames, Florence is still showing an ovular shaped eye, but it's really smoothed out now, not like the ragged edged eye of a few hours ago. Also looks like she's pushing back and filling out some of that compression in the SW quad. I would guess pressure will drop some in the next 12 hours.

[aperson]

I've been interested in the 2 hours of intense outer rainband lightning going up:



This (not open access ) paper indicates that this may be a leading indicator of RI in the 12-18 hour range: https://agupubs.onlinelibrary.wiley.com ... 17JD027072

Inner Core (Outer Rainband) flash density decreases (increases) 12–18 h preceding the onset of RI, while Inner Core (Outer Rainband) flash density increases (decreases) 6–12 h prior to TC weakening.

[MaineWeatherNut]

My 2am update on Hurricane Florence... A little late being posted here but better late then never. Tropical Storm conditions will start to spread on shore on Thursday so you guys have today to finish your preparations before conditions start going down hill.

https://www.youtube.com/watch?v=JsXk3MbwKJg

[TheDreamTraveler]

Kinda sucks that recon is leaving the storm as soon as it starts looking better.

[Blown Away]

The 00z GFS/Euro going to make the NHC 5am disco even more crazy... The track was such a sure thing even out at 60W... Wow, incredible model runs and uncertainty... Those Euro ensembles have trended S from 12z to 00z...

[caneman]

The 00z GFS/Euro going to make the NHC 5am disco even more crazy... The track was such a sure thing even out at 60W... Wow, incredible model runs and uncertainty... Those Euro ensembles have trended S from 12z to 00z...

Any chance of this dipping down to Georgia or even North Florida? The trend throughout has been south

[tarheelprogrammer]

So, this is trending away from Wilmington?

[Blown Away]

The 00z GFS/Euro going to make the NHC 5am disco even more crazy... The track was such a sure thing even out at 60W... Wow, incredible model runs and uncertainty... Those Euro ensembles have trended S from 12z to 00z...

Any chance of this dipping down to Georgia or even North Florida? The trend throughout has been south

Model runs so wild, I think anything may be on table, remember the points off SC/GA are 120 hrs away, 5 days lots of potential uncertainty.

[Hammy]

So, this is trending away from Wilmington?

Yes and no depending on what metric you're looking at--some of the models are trending away from coming onshore and stalling out inland, and towards the eyewall sitting over the southern NC coast for days.

[southerngale]

564
WTNT41 KNHC 120853
TCDAT1

Hurricane Florence Discussion Number 52
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Wed Sep 12 2018

The eye of Florence remains very distinct in infrared satellite
imagery this morning. There has been little change to the cloud top
temperatures surrounding the eye overnight, however, the overall
cloud shield and central dense overcast has become slightly more
symmetric. An Air Force Reserve Hurricane Hunter aircraft that was
in the hurricane until just after midnight measured a peak 700-mb
flight-level wind of 130 kt, and a SFMR wind of 107 kt in the
northeast eyewall. A blend of these data and recent subjective and
objective satellite intensity estimates supports an initial wind
speed of 115 kt. Florence will be moving over sea surface
temperatures of around 29C and through an area of low vertical wind
shear during the next day or so. These conditions favor some
strengthening, but eyewall replacement cycles could cause some
fluctuations in intensity during that time. After that time, an
increase in southwesterly shear, upwelling, and interaction with
land is likely to lead to some weakening, however, Florence is
expected to remain a dangerous major hurricane as it approaches the
coastline. The new NHC intensity forecast is near the higher
statistical guidance through 48 hours, then follows the trend of
the decay SHIPS model after that time.

Florence is moving west-northwestward or 300 degrees at 15 kt.
There has been no change to the track forecast or reasoning for the
first 36-48 hours, as Florence will continue to be steered
west-northwestward to northwestward around the southwestern portion
of a mid-level ridge centered northeast of Bermuda. By late
Thursday, a mid-level ridge is forecast to begin building over the
east-central United States, which is expected to cause Florence
to slow down significantly by 48 hours. The track guidance is in
good agreement through the first couple of days of the forecast
period, and the NHC track forecast again brings the center of the
hurricane very close to the coasts of North and South Carolina
within 48 hours. Later in the period, the dynamical model spread
increases but most of the guidance has continued its southward
shift, and now take Florence southwestward near the coast of South
Carolina by day 4. The NHC track has been adjusted southward at
days 4 and 5, and is a little north of the consensus out of respect
for continuity, however, the GFS, ECMWF, and the ECMWF ensemble mean
is south of the NHC track forecast, and additional southward
adjustment may be warranted in future advisories.

It is important for users to realize that significant impacts extend
well away from the center of Florence, and serious hazards such as
a dangerous storm surge and flooding rains will cover a large area
regardless of exactly where the center moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along
portions of the coastlines of South Carolina and North Carolina, and
a Storm Surge Warning is in effect for a portion of this area. All
interests from South Carolina into the mid-Atlantic region should
complete preparations and follow any advice given by local
officials.

2. Life-threatening, catastrophic flash flooding and significant
river flooding is likely over portions of the Carolinas and
Mid-Atlantic states from late this week into early next week, as
Florence is expected to slow down as it approaches the coast and
moves inland.

3. Damaging hurricane-force winds are likely along portions of the
coasts of South Carolina and North Carolina, and a Hurricane Warning
is in effect. Strong winds could also spread inland into portions
of the Carolinas.

4. Large swells affecting Bermuda and portions of the U.S. East
Coast will continue this week, resulting in life-threatening surf
and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 29.0N 70.1W 115 KT 130 MPH
12H 12/1800Z 30.3N 72.1W 120 KT 140 MPH
24H 13/0600Z 32.0N 74.4W 125 KT 145 MPH
36H 13/1800Z 33.2N 76.1W 120 KT 140 MPH
48H 14/0600Z 33.8N 77.3W 105 KT 120 MPH...NEAR THE COAST
72H 15/0600Z 33.8N 78.2W 85 KT 100 MPH...NEAR THE COAST
96H 16/0600Z 33.6N 79.7W 45 KT 50 MPH...INLAND
120H 17/0600Z 34.2N 82.7W 25 KT 30 MPH...INLAND

$$
Forecaster Brown

[caneman]

From the 5:00 am disco:
Later in the period, the dynamical model spread
increases but most of the guidance has continued its southward
shift, and now take Florence southwestward near the coast of South
Carolina by day 4. The NHC track has been adjusted southward at
days 4 and 5, and is a little north of the consensus out of respect
for continuity, however, the GFS, ECMWF, and the ECMWF ensemble mean
is south of the NHC track forecast, and add

[southerngale]

342
WTNT31 KNHC 120852
TCPAT1

BULLETIN
Hurricane Florence Advisory Number 52
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Wed Sep 12 2018

...DANGEROUS FLORENCE HEADING TOWARD THE U.S. EAST COAST...
...EXPECTED TO BRING LIFE-THREATENING STORM SURGE AND RAINFALL TO
PORTIONS OF THE CAROLINAS AND MID-ATLANTIC STATES...


SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...29.0N 70.1W
ABOUT 575 MI...925 KM SE OF CAPE FEAR NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...946 MB...27.94 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

A Tropical Storm Warning has been issued from north of Duck North
Carolina to the North Carolina-Virginia border. The Hurricane
Watch for this area has been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds, including the Neuse and Pamlico
Rivers

A Storm Surge Watch is in effect for...
* Edisto Beach South Carolina to South Santee River South Carolina
* North of Duck North Carolina to the North Carolina/Virginia border

A Hurricane Warning is in effect for...
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds

A Hurricane Watch is in effect for...
* Edisto Beach South Carolina to South Santee River South Carolina

A Tropical Storm Warning is in effect for...
* North of Duck North Carolina to the North Carolina/Virginia border

A Tropical Storm Watch is in effect for...
* North of the North Carolina/Virginia border to Cape Charles Light
Virginia
* Chesapeake Bay south of New Point Comfort

Interests elsewhere in the southeastern and mid-Atlantic states
should monitor the progress of Florence.

A Storm Surge Warning means there is a danger of life-threatening
inundation, from rising water moving inland from the coastline,
during the next 36 hours in the indicated locations. For a
depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov. This is a life-threatening situation. Persons
located within these areas should take all necessary actions to
protect life and property from rising water and the potential for
other dangerous conditions. Promptly follow evacuation and other
instructions from local officials.

A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.

A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area. A warning is typically issued
36 hours before the anticipated first occurrence of tropical-storm-
force winds, conditions that make outside preparations difficult or
dangerous. Preparations to protect life and property should be
rushed to completion.

A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.

[caneman]

Based on that I'd say Georgia and Jax arent out of the woods. The entirety of Florence's life has indicated a southward trend and that seems like it will continue

[jdjaguar]

Based on that I'd say Georgia and Jax arent out of the woods. The entirety of Florence's life has indicated a southward trend and that seems like it will continue

Agree.

Euro actually has a 977 center right over savannah day 5

[aperson]

I'm surprised this advisory went with 115kt. Florence has consistently had windspeeds higher than cloud tops would suggest and the current appearance is T6.5 trending toward 7.0. It has improved considerably since recon. I figured they would keep it at 120kt.