ATL: FLORENCE - Post-Tropical - Discussion

[SconnieCane]

Ya, we think forecasting a hurricane's path is hard, just try intensity!

[Blown Away]

Does NHC have the floaters anymore? I know Tidbits does...

[AnnularCane]

Ya, we think forecasting a hurricane's path is hard, just try intensity!

Florence: "Unfavorable conditions? What unfavorable conditions?"

Obviously there is still a lot to learn about what makes these storms tick!

[txwatcher91]

:uarrow: Looks like it's cleared out too.

It’s actually looking much more ragged on the latest IR frames. West side of CDO is collapsing and convection isn’t nearly as deep either.

[EquusStorm]

Eye certainly remains impressive but seeing how close it is to the SW of the CDO now makes it clear that southwesterly shear is finally trying to wrangle it in some. Still am finding it hard to process that it managed to reach Cat 4 before feeling it, though. Going to be one of the landmark storms of the year even if it misses all land just for its utter defiance of forecast intensity and its unprecedented lat/long Cat 4 presence. That's the main reason I am enamored with the tropics, when fascinating storms like this decide to ply the basin.

[StormyWaters93]

Eye certainly remains impressive but seeing how close it is to the SW of the CDO now makes it clear that southwesterly shear is finally trying to wrangle it in some. Still am finding it hard to process that it managed to reach Cat 4 before feeling it, though. Going to be one of the landmark storms of the year even if it misses all land just for its utter defiance of forecast intensity and its unprecedented lat/long Cat 4 presence. That's the main reason I am enamored with the tropics, when fascinating storms like this decide to ply the basin.

I agree. Whether this makes landfall or not, this storm is one to study and one that will be talked about for awhile.

Sent from my SM-S727VL using Tapatalk

[gatorcane]

We may look back at this storm and say thanks for it defying the models and forecasters and intensifying much more than expected in the open Atlantic. It could be the reason why it ultimately misses the CONUS if it ends up missing.

[Hammy]

Does NHC have the floaters anymore? I know Tidbits does...

I think all the GOES-East SSD sites (including the NWS office floaters) were shut down once GOES-16 became operational

[LarryWx]

48H 05/1800Z 21.5N 48.4W 50 KT 60 MPH

This seems quite a bit off for an advisory issued only 48 hours ago. Not even half of the current intensity.

So, 48 hours ago it was projected to be at only 21.5 N while already at 48.4 W. Instead she’s already up to 23.1 N and only to 46.9 W as of 8PM today, which means she’s nearly 150 miles NE of her progged 48 hour NHC position. That’s not chickenfeed. Is this miss due mainly to the strength being way underforecasted? Does this mean that over the next couple of days these misses to the NE are liable to continue? Remember folks that 30N has been established by the models as a crucial latitude to reach before 60W to give a great chance for recurving before hitting the US.

[Bocadude85]

48H 05/1800Z 21.5N 48.4W 50 KT 60 MPH

This seems quite a bit off for an advisory issued only 48 hours ago. Not even half of the current intensity.

So, 48 hours ago it was projected to be at only 21.5 N while already at 48.4 W. Instead she’s already up to 23.1 N and only to 46.9 W as of 8PM today, which means she’s nearly 150 miles NE of her progged 48 hour NHC position. That’s not chickenfeed. Is this miss due mainly to the strength being way underforecasted? Does this mean that over the next couple of days these misses to the NE are liable to continue? Remember folks that 30N has been established by the models as a crucial latitude to reach before 60W to give a great chance for recurving before hitting the US.

The question is what if Florence starts a WSW move like some of the models are suggesting, would the loss of latitude even out the recent latitude gain?

[AutoPenalti]

It's about to lose it's core real soon...look at the SW quadrant.



Shear is at 25kts...

[JaxGator]

It's about to lose it's core real soon...look at the SW quadrant.

Ouch.. She/it has persevered all day and has put on a show. We'll see how much she weakens before restrengthening again.

[cycloneye]

Hurricane Florence Discussion Number 27
NWS National Hurricane Center Miami FL AL062018
1100 PM AST Wed Sep 05 2018

It appears that southwesterly shear is finally affecting Florence.
The cloud pattern has become asymmetric this evening, with the
northeastern quadrant growing at the expense of the southwestern
one, along with warming cloud tops noted across the central dense
overcast. Satellite intensity estimates are a bit lower than
before, so the initial wind speed is reduced to 110 kt.

The current shear is forecast to persist by the global models during
the next day or two until an upper-level low cuts off to south of
Florence, which will likely reduce the shear. This, in combination
with much warmer waters in the path of the hurricane, should set the
stage for restrengthening. At long range, a rather large upper-level
anticyclone is forecast to form near Florence, which would provide
ample opportunity for the hurricane to regain its former strength
and grow in size. Thus, the official forecast shows slow weakening
in response to the initial shear, then levels off, with a
significant increase in strength predicted by day 5. This solution
is very close to the previous NHC advisory, but not quite as high as
the HWRF and HMON models at long range.

Florence has been moving more to the right during the past several
hours, likely due to the vortex attempting to stay vertically
aligned in the face of the southwesterly shear, but a longer-term
motion is 310 degrees at 10 kt. A mid-level ridge is forecast to
strengthen to the north and northwest of Florence, causing the
hurricane to turn west- northwestward by Friday and even westward by
the weekend. It appears that a mid-latitude trough over the
northwestern Atlantic in a few days will likely miss Florence, with
the only perceivable effects on the hurricane being a decrease in
forward speed. The net result is that the model guidance continues
to trend westward at long range, and the official forecast follows
suit, lying just north of the model consensus in deference to the
ECMWF deterministic model and ensemble mean.

It should be noted that 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,
resulting in life-threatening surf and rip currents on the island.
Swells from Florence could also reach the U.S. East Coast by early
next week.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 23.4N 47.2W 110 KT 125 MPH
12H 06/1200Z 24.2N 48.4W 105 KT 120 MPH
24H 07/0000Z 25.0N 49.9W 100 KT 115 MPH
36H 07/1200Z 25.5N 51.6W 95 KT 110 MPH
48H 08/0000Z 25.7N 53.2W 95 KT 110 MPH
72H 09/0000Z 26.1N 55.7W 100 KT 115 MPH
96H 10/0000Z 27.2N 58.1W 105 KT 120 MPH
120H 11/0000Z 29.0N 62.0W 115 KT 130 MPH

$$
Forecaster Blake

[Ptarmigan]

First major hurricane of the Atlantic 2018 season?

Almost a certainty

Well, it is now a Category 4 hurricane.

[Bocadude85]

The 11pm forecast track from the NHC has been shifted 2 degrees to the west at day 5...

[gatorcane]

Small storms like Florence can weaken just as quickly as they strengthen and now the shear appears to be taking its toll. For perspective on the size of Florence:

http://rammb.cira.colostate.edu/ramsdis ... display=24

[AutoPenalti]

Florence has been moving more to the right during the past several
hours, likely due to the vortex attempting to stay vertically
aligned in the face of the southwesterly shear, but a longer-term
motion is 310 degrees at 10 kt. A mid-level ridge is forecast to
strengthen to the north and northwest of Florence, causing the
hurricane to turn west- northwestward by Friday and even westward by
the weekend. It appears that a mid-latitude trough over the
northwestern Atlantic in a few days will likely miss Florence, with
the only perceivable effects on the hurricane being a decrease in
forward speed. The net result is that the model guidance continues
to trend westward at long range, and the official forecast follows
suit, lying just north of the model consensus in deference to the
ECMWF deterministic model and ensemble mean.

It should be noted that 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,
resulting in life-threatening surf and rip currents on the island.
Swells from Florence could also reach the U.S. East Coast by early
next week.

Bolded seems pretty interesting.

[Ken711]

Small storms like Florence can weaken just as quickly as they strengthen and now the shear appears to be taking its toll. For perspective on the size of Florence:

http://rammb.cira.colostate.edu/ramsdis ... display=24

That link is loading for me.

[AutoPenalti]

Small storms like Florence can weaken just as quickly as they strengthen and now the shear appears to be taking its toll. For perspective on the size of Florence:

http://rammb.cira.colostate.edu/ramsdis ... display=24

That link is loading for me.

[JaxGator]

Florence has been moving more to the right during the past several
hours, likely due to the vortex attempting to stay vertically
aligned in the face of the southwesterly shear, but a longer-term
motion is 310 degrees at 10 kt. A mid-level ridge is forecast to
strengthen to the north and northwest of Florence, causing the
hurricane to turn west- northwestward by Friday and even westward by
the weekend. It appears that a mid-latitude trough over the
northwestern Atlantic in a few days will likely miss Florence, with
the only perceivable effects on the hurricane being a decrease in
forward speed. The net result is that the model guidance continues
to trend westward at long range, and the official forecast follows
suit, lying just north of the model consensus in deference to the
ECMWF deterministic model and ensemble mean.

It should be noted that 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,
resulting in life-threatening surf and rip currents on the island.
Swells from Florence could also reach the U.S. East Coast by early
next week.

Bolded seems pretty interesting.

So, in a sense, the hurricane was playing catch up? At least that what it sounds like.