ATL: FLORENCE - Post-Tropical - Discussion

[txwatcher91]

Most recent morning visibles indicate a turn may have begun to the WNW. If this indeed isn't a wobble then that would be well ahead of the GFS schedule and more in agreement with the models that threaten the East Coast. Furthermore the GFS doesn't weaken the system as much as other models and the structure of Florence has deteriorated rapidly overnight and this morning. She's likely a cat 1 right now and could weaken to a tropical storm today if the heavy shear persists. FWIW the 06z GEFS also shifted west a bit.

[ava_ati]

still looks NW to me, will need a few more frames to know for sure

[txwatcher91]

still looks NW to me, will need a few more frames to know for sure

Check out the microwave on this loop, you can see the most recent frames it appears to be shifting to a more wnw heading here.

http://tropic.ssec.wisc.edu/real-time/m ... hr_07.html

[TheStormExpert]

Wind shear is finally affecting Florence this morning, the westward track begin as advertised by the models later today or tomorrow

Rather similar to the UkMET which has been stuck on a weaker Florence

It might initially have a weaker Florence, but it re-strengthens it on approach to the Bahamas.

[GCANE]

Latest Archer Map

X marks forecasted locations.
Circles are estimated satellite fixes.

[SFLcane]

Wind shear is finally affecting Florence this morning, the westward track begin as advertised by the models later today or tomorrow

Rather similar to the UkMET which has been stuck on a weaker Florence

It might initially have a weaker Florence, but it re-strengthens it on approach to the Bahamas.

Yep just posted some UKMET maps in florence models page.

[TheStormExpert]

Latest saved satellite loop.

[Kazmit]

Wow, the shear really messed it up. It will interesting to see how it reorganizes once the shear abates.

[SconnieCane]

Yeah Florence looks like one sick puppy* this morning, but before long water will be plenty warm to fix her right up if the shear abates.

Is it me or has motion stopped, maybe a slight almost due northward drift? Seems to be related to the core trying to keep rotating against the shear. Short term slow/erratic movement could also portend an upcoming change in direction.

*Definitely not a 100kt Cat 3, and hasn't been since probably before the 5AM AST advisory went out.

[tolakram]

Latest Archer Map

X marks forecasted locations.
Circles are estimated satellite fixes.

Where can I find this map?

[Blown Away]

WNW turn has begun.

[GCANE]

Latest Archer Map

X marks forecasted locations.
Circles are estimated satellite fixes.

Where can I find this map?

http://tropic.ssec.wisc.edu/real-time/a ... ndex.shtml

[SFLcane]

Have a feeling we might be tracking a naked swirl later today..

[RL3AO]

I'm curious to see the weakening trend when it starts. Sometimes these storms come down as quick as the go up.

And 18 hours later...

[PavelGaborik10]

Yikes that is one seriously pitiful looking Hurricane.

[PavelGaborik10]

I'm curious to see the weakening trend when it starts. Sometimes these storms come down as quick as the go up.

And 18 hours later...

Do you think it'll bounce back quickly? It looks like an absolute Trainwreck right now and shear doesn't seem to be letting up.

[cycloneye]

Hurricane Florence Discussion Number 29
NWS National Hurricane Center Miami FL AL062018
1100 AM AST Thu Sep 06 2018

Vertical shear has increased since yesterday, which has caused a
degradation of Florence's structure and a decrease in its maximum
winds. The cloud-filled eye has been eroded over the past hour or
so, and the deep convection is no longer symmetric, with the
low-level circulation peeking out from under the higher clouds.
Dvorak CI numbers from TAFB and SAB have fallen to T5.0-5.5 (90-100
kt), while the objective numbers from UW-CIMSS support 70-90 kt.
The initial intensity is set at 90 kt, near the middle of this wide
range of estimates.

The intensity forecast has been somewhat of a self-defeating
prophecy due to the nuances of the environmental shear. Even though
Florence was able to rapidly intensify yesterday in an area just
south of a zone of strong shear, the hurricane's stronger-than-
expected intensity caused it to move more poleward, into that
stronger shear. Right now, shear analyses range anywhere from
25-30 kt, and the latest available guidance suggests that this
level of shear should continue for another 12-24 hours. As a
result, continued weakening is forecast over the next day or so.
After 36 hours, Florence is likely to encounter an upper-level
environment that is more conducive for reintensification. The NHC
forecast is adjusted downward toward the newest consensus aids,
especially during the first 48 hours, but it still shows Florence
reaching major hurricane strength again by days 4 and 5.

Florence's forward motion has slowed just a little to 9 kt toward
the northwest (315 degrees). A mid-level ridge is building to the
north, which is likely to cause the hurricane to turn westward by
36 hours, with that motion continuing through about day 3. After
that time, there is still considerable uncertainty in the evolution
of the steering pattern over the western Atlantic, especially on day
4. On one hand, the GFS and HWRF dig a strong shortwave trough over
Atlantic Canada by Monday, creating a break in the ridge which would
allow Florence to turn northwestward. On the other hand, the ECMWF
and UKMET both have weaker troughs and maintain stronger ridging
over the northwestern Atlantic, allowing Florence to maintain a
westward or west-northwestward course. All the models show a
mid-level high over the western Atlantic by Tuesday. Due to typical
biases among these models in the part of the Atlantic, we prefer to
be between the GFS and ECMWF solutions at this time, which places
the official NHC track forecast close to the TVCN multi-model
consensus and just north of HCCA.

There is still considerable model ensemble spread for Florence's
track beyond day 5. Given the large uncertainty at these time
ranges, it is far too soon to speculate what, if any, impacts
Florence may have on the U.S. East Coast next week. Regardless of
Florence's eventual track, large swells emanating from the hurricane
will reach Bermuda beginning on Friday and portions of the U.S. East
Coast this weekend, resulting in life-threatening surf and rip
currents.

FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 24.6N 48.6W 90 KT 105 MPH
12H 07/0000Z 25.2N 49.8W 80 KT 90 MPH
24H 07/1200Z 25.6N 51.3W 75 KT 85 MPH
36H 08/0000Z 25.6N 52.6W 75 KT 85 MPH
48H 08/1200Z 25.7N 54.0W 80 KT 90 MPH
72H 09/1200Z 26.3N 56.4W 90 KT 105 MPH
96H 10/1200Z 28.0N 59.5W 100 KT 115 MPH
120H 11/1200Z 29.5N 65.0W 105 KT 120 MPH

$$
Forecaster Berg

[Kazmit]

How long until the shear is supposed to drop?

[plasticup]

I'm curious to see the weakening trend when it starts. Sometimes these storms come down as quick as the go up.

And 18 hours later...

NHC says it will spin up again when it moves out of the shear in 36 hours. Should be over warm SST again. Do you think it will spin up as quickly as last time, or more modestly like the NHC predicts?

[Bocadude85]

Florence is really taking a beating this morning, it appears that half of Florence’s coc is exposed...she also seems to be on a more wnw heading.