ATL: FLORENCE - Post-Tropical - Discussion

[Aric Dunn]

looking at the low level cloud pattern.. appears a wsw to sw motion has started.

[Hurricane Andrew]

From NHC's 11 PM Disco:

Some further weakening is anticipated since the shear isn't forecast
to change much in the short term. However, all of the global models
show a significant reduction of shear during the next several days,
especially later this weekend. In combination with waters warming
to near 29C, these conditions should promote strengthening into a
hurricane again in a day or two and a major hurricane by early next
week. The intensity guidance is higher than the last cycle at long
range, which is hard to argue with considering the large upper-level
anticyclone forecast in the vicinity of Florence. The NHC intensity
forecast follows the trend of the previous prediction, a bit
elevated from the previous forecast at days 4 and 5, although still
below the intensity guidance.

[LarryWx]

Is it my imagination or is Florence already beginning to restrengthen??

IR loop:
https://www.tropicaltidbits.com/sat/sat ... product=ir

Edit: And if so, has she possibly jumped further north?

[HurricaneIrma]

Is it my imagination or is Florence already beginning to restrengthen??

IR loop:
https://www.tropicaltidbits.com/sat/sat ... product=ir

Edit: And if so, has she possibly jumped further north?

I don't think so not imho

[1900hurricane]

The center still looks on the SW side of the convection when overlying band 13 onto band 7 using SLIDER. This appears consistent with recent microwave data.

[Hurricane Andrew]

I wonder how long it will take the MLC and LLC to re-align.

[GCANE]

Still hanging in there with convection firing nearly at the CoC.
Rain rate increasing to strong levels.
Will be hitting water with more available heat in about 48hrs.
GFS has it moving into a more conducive shear environment then.
Keeping an eye on how 355K PV evolves from that.

[Hurricane Andrew]

Yeah, she's fighting GCANE, but that center is still displaced to the SE of the heavier convection. I wouldn't be surprised (and this is an unprofessional opinion) to see her weaken a little further to a mid-range tropical storm as she cycles through. How fast she can reintensify during the D2-D5 lead time will be critical.

[cycloneye]

Tropical Storm Florence Discussion Number 32
NWS National Hurricane Center Miami FL AL062018
500 AM AST Fri Sep 07 2018

Florence's structure continues to be negatively affected by strong
southwesterly shear. Cloud tops have generally warmed over the
past 6 hours, and recent microwave data show that the low-level
circulation center of Florence is displaced nearly 20 nmi to the
southwest of the mid-level center. Satellite intensity estimates
have decreased since last night, and now support an initial
intensity of 55 kt.

Based on GFS and ECMWF SHIPS diagnostic output, the southwesterly
shear is near its peak now, and should gradually decrease over the
next 24 to 36 h. All of the intensity guidance shows little change
in intensity through that time. From 48 h onward, a low shear/warm
SST environment should allow the tropical storm to re-strengthen.
However, the extent and timing of the strengthening varies greatly
from model to model, with the dynamical models generally showing
more intensification, and sooner, than the statistical models. As
has been the case for most of Florence's existence thus far,
confidence in the intensity forecast, especially beyond 36 h, is
low. The new official forecast is a little lower than the previous
advisory for the first 48 h, but close to it after that, and lies
between the more aggressive HCCA and less aggressive IVCN consensus
aids.

Nighttime Proxy-Vis and earlier microwave imagery indicate that
Florence has turned westward, with an estimated initial motion of
275/6 kt. Most of the track guidance has shifted slightly toward the
southwest, so the NHC track forecast has also been nudged in that
direction. Over the next 3 days of the forecast, Florence should be
steered generally westward, and then west-northwestward, by a
mid-level ridge to its north. By days 4 and 5, a developing
mid-latitude trough could create a weakness in this ridge and allow
Florence to move more toward the northwest, but there is still
considerable uncertainty in the global models and their ensembles
regarding the strength of the ridge and if the aforementioned trough
will have any notable impact on the track of Florence. The NHC
forecast follows HCCA very closely, and is also near the middle of
the large combined envelope of the GFS, UKMET, and ECMWF ensembles.

Key Messages:

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

2. There is still very large uncertainty in Florence's track
beyond day 5, and it is too soon to determine what, if any, other
impacts Florence could have on the U.S. East Coast next week.

3. Since we are near the peak of hurricane season, this is a good
time for everyone who lives in a hurricane-prone area to ensure they
have their hurricane plan in place.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 25.1N 50.7W 55 KT 65 MPH
12H 07/1800Z 25.1N 51.8W 55 KT 65 MPH
24H 08/0600Z 25.0N 53.2W 55 KT 65 MPH
36H 08/1800Z 25.0N 54.3W 60 KT 70 MPH
48H 09/0600Z 25.1N 55.4W 70 KT 80 MPH
72H 10/0600Z 26.2N 58.3W 95 KT 110 MPH
96H 11/0600Z 27.5N 63.5W 110 KT 125 MPH
120H 12/0600Z 30.0N 70.0W 110 KT 125 MPH

$$
Forecaster Zelinsky

[GCANE]

Yeah, she's fighting GCANE, but that center is still displaced to the SE of the heavier convection. I wouldn't be surprised (and this is an unprofessional opinion) to see her weaken a little further to a mid-range tropical storm as she cycles through. How fast she can reintensify during the D2-D5 lead time will be critical.

I am keeping an eye on a possible ULL evolving just to the north today.
GFS forecasts it to move to the east which should help ventilation.
In the long run, it may merge with a deeper ULL and possibly set up a strong outflow channel.
Mid-level moisture and TPW entrainment looks marginally conducive until Flo gets near the Gulf Stream.
At that point, everything seems to kick in, including in an anti-cyclone over head and nearly ideal 355K PV ring structure.
All this according to GFS.

[lando]

Yesterday, Global model consensus (minus uk) was NC brush/ landfall
today it is SC landfall
Tomorrow....? NFL, GA? Who knows

[Hurricane Andrew]

Yeah, she's fighting GCANE, but that center is still displaced to the SE of the heavier convection. I wouldn't be surprised (and this is an unprofessional opinion) to see her weaken a little further to a mid-range tropical storm as she cycles through. How fast she can reintensify during the D2-D5 lead time will be critical.

I am keeping an eye on a possible ULL evolving just to the north today.
GFS forecasts it to move to the east which should help ventilation.
In the long run, it may merge with a deeper ULL and possibly set up a strong outflow channel.
Mid-level moisture and TPW entrainment looks marginally conducive until Flo gets near the Gulf Stream.
At that point, everything seems to kick in, including in an anti-cyclone over head and nearly ideal 355K PV ring structure.
All this according to GFS.

Indeed. My personal thoughts (again, I am not a meteorological professional) are that we see moderate restrengthening from D2-D4, with the bulk of any deep intensification (say, to a major hurricane) occurring on D5, and perhaps D6. The Gulf Stream is 28.5-29.5º right now. That reminds me, does anyone have a link to those maps that measure OHC/SSTs and prog how strong a storm the ocean conditions could potentially support?

[JtSmarts]

GFS and Euro both have potential US coast impacts next Thursday (6 days away). Won't be long til that cone starts to kiss the CONUS.

[NDG]

Like I mentioned last night the stout ridging pattern over the NW Atlantic into the NE US/SE Canada is no joke, it has been on place more often than not during the past month, after the shortwave trough passes by this weekend to the north of Florence the stout ridge pattern will immediately go back in place.
Florence will have no option but to keep tracking closer to the eastern US.

[GCANE]

Yeah, she's fighting GCANE, but that center is still displaced to the SE of the heavier convection. I wouldn't be surprised (and this is an unprofessional opinion) to see her weaken a little further to a mid-range tropical storm as she cycles through. How fast she can reintensify during the D2-D5 lead time will be critical.

I am keeping an eye on a possible ULL evolving just to the north today.
GFS forecasts it to move to the east which should help ventilation.
In the long run, it may merge with a deeper ULL and possibly set up a strong outflow channel.
Mid-level moisture and TPW entrainment looks marginally conducive until Flo gets near the Gulf Stream.
At that point, everything seems to kick in, including in an anti-cyclone over head and nearly ideal 355K PV ring structure.
All this according to GFS.

Indeed. My personal thoughts (again, I am not a meteorological professional) are that we see moderate restrengthening from D2-D4, with the bulk of any deep intensification (say, to a major hurricane) occurring on D5, and perhaps D6. The Gulf Stream is 28.5-29.5º right now. That reminds me, does anyone have a link to those maps that measure OHC/SSTs and prog how strong a storm the ocean conditions could potentially support?

Maybe this one:
http://wxmaps.org/pix/hurpot

[Hurricane Andrew]

Maybe this one:
http://wxmaps.org/pix/hurpot

Yes! Thank you!

[JtSmarts]

Overnight/Morning Summary:

0z Euro: Landfall Near Myrtle Beach (Was 962MB a few hours prior to landfall) - Afternoon 9/13
6Z GFS: Landfall OBX (939mb) then up towards VA - Morning 9/13
0z CMC: Landfall near Morehouse City, NC (986mb) - Early Morn 9/14

[Hurricane Andrew]

Am I crazy, or does this suddenly look not-so-bad on Visible?

Definitely rocking a new CDO, although I think it might be displaced a bit from the LLC.

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

[northjaxpro]

Like I mentioned last night the stout ridging pattern over the NW Atlantic into the NE US/SE Canada is no joke, it has been on place more often than not during the past month, after the shortwave trough passes by this weekend to the north of Florence the stout ridge pattern will immediately go back in place.
Florence will have no option but to keep tracking closer to the eastern U.S.
]

Yes indeed NDG. Very strong, anomalous ridging in place across the Northwest Atlantic. A very ominous situation unfolding potentially for the entire U.S. East Coast next 5-7 days. I am getting more uncomfortable by the day for sure!

[Blown Away]

Over the next 3 days of the forecast, Florence should be
steered generally westward, and then west-northwestward, by a
mid-level ridge to its north. By days 4 and 5, a developing
mid-latitude trough could create a weakness in this ridge and allow
Florence to move more toward the northwest, but there is still
considerable uncertainty in the global models and their ensembles
regarding the strength of the ridge and if the aforementioned trough
will have any notable impact on the track of Florence. The NHC
forecast follows HCCA very closely, and is also near the middle of
the large combined envelope of the GFS, UKMET, and ECMWF ensembles.

That keeps Florida - Maine still in play IMO.