ATL: KARL - Post-Tropical - Discussion

[CYCLONE MIKE]

First significant early season cold front sweeps south to the gulf coast and off the east coast this weekend. Karl will have nowhere to go but up and out. Gfs depicts it pretty well. Stalls out like running into a brick wall then shunted ene.

[stormreader]

Anybody notice the ECMWF seems to be spinning off a secondary weak vorticity to the south of the main vorticity in today's run? I also noticed the GFS was doing something similar in yesterday's runs but thought it was some kind of glitch or something. What exactly would cause this I wonder?

You mean that shaded area which heads into the Bahamas? Makes you wonder if the model is trying to make sense of a possibly weaker Karl (maybe even at wave/invest strength taking a more southerly route through the Bahamas (such as Hermine did). Just a thought.

[cycloneye]

TROPICAL STORM KARL DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016
1100 PM AST SUN SEP 18 2016

Karl is a poorly organized tropical storm. Satellite data indicate
that the low-level center is exposed to the southwest of a few
patches of deep convection. The initial intensity is again held at
35 kt, in agreement with the earlier scatterometer data and a Dvorak
classification from TAFB. The cyclone continues to struggle in an
environment of southwesterly shear and dry air. In fact, total
precipitable water imagery shows dry air wrapping around the west
and south sides of the circulation. The models indicate that the
shear should lower on Monday, and remain relatively light during the
next several days. Since Karl is expected to track over
progressively warmer waters, between 28-30 deg C, and move into a
more conducive atmospheric environment, strengthening seems likely.
The NHC intensity forecast is largely an update of the previous one,
but it is a touch lower at the 12-h point given the current poor
initial structure of Karl. This forecast is in best agreement with
the SHIPS model.

The system is moving westward at 13 kt, and that general motion
should continue for the next 12-24 hours as Karl remains on the
south side of a subtropical ridge over the central Atlantic. A
west-northwestward motion is expected to begin by Monday night,
followed by a turn to the northwest by mid-week when the cyclone
moves toward a weakness in the ridge. Although the models
agree on the overall scenario, there is a fair amount of spread by
the end of the forecast period. The NHC track forecast is slightly
faster than the model consensus, giving a little more weight to the
GFS and ECMWF models.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0300Z 18.3N 46.3W 35 KT 40 MPH
12H 19/1200Z 18.5N 48.3W 35 KT 40 MPH
24H 20/0000Z 19.1N 50.9W 40 KT 45 MPH
36H 20/1200Z 19.8N 53.4W 45 KT 50 MPH
48H 21/0000Z 20.7N 55.9W 50 KT 60 MPH
72H 22/0000Z 23.1N 60.9W 60 KT 70 MPH
96H 23/0000Z 26.5N 65.0W 70 KT 80 MPH
120H 24/0000Z 28.8N 66.9W 80 KT 90 MPH

$$
Forecaster Cangialosi

[AutoPenalti]

First significant early season cold front sweeps south to the gulf coast and off the east coast this weekend. Karl will have nowhere to go but up and out. Gfs depicts it pretty well. Stalls out like running into a brick wall then shunted ene.

Yay for cold fronts. If it even shows up.

[sunnyday]

Is there any chance Karl doesn't go up and out after the stall?

[gatorcane]

I think I see the LLC on the left side of the convection popping on the south side...

http://rammb.cira.colostate.edu/ramsdis ... display=12

[Hurricaneman]

This may need to be watched in Bermuda and maybe farther west depending on the trough ridge situation but as modeled Bermuda is at most risk at the moment

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the National Hurricane Center and National Weather Service.

[SeGaBob]

Is there any chance Karl doesn't go up and out after the stall?

No

[Hurricaneman]

Is there any chance Karl doesn't go up and out after the stall?

No

But Bermuda may be under the gun for the first time since Gonzalo in 2014

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the National Hurricane Center and National Weather Service.

[JaxGator]

Karl may have regained a circulation, but it had better improve its convective activity if it expects to keep it.

Seems like the MU scenario of this reverting between a depression and a wave is verifying nicely

What are your thoughts of the GFS showing a stronger storm south of Bermuda at 12z? Don't know if it's showing it now though.

I want to make sure this clears the Caribbean first. This could reform to the south based upon the WINDSAT

Thank you for the reply. That'll be interesting seeing what he does regarding the Caribbean. Will be watching closely.

[AutoPenalti]

Is there any chance Karl doesn't go up and out after the stall?

No

Are you basing that on the models that are currently out of sorts? Or..?

[ScottNAtlanta]

I'm not buying the recurve yet for a couple of reasons.
I think the troff that is supposed to pick it up is over done. A front getting that far south is rare this time of year and troffs tend to lift out rather quickly. I dont see it dipping as far south as what the modeling says right now. Also, I dont think Karl will be as strong as the models are indicating thus a more westward direction and a system that wont feel the troff as much. We will see but the trend with some of the models has been westward. Its a wait and see. Timing will be everything on this one. If the troff gets that far south, there will be a short window to pick up Karl. If one or the other is too fast/slow they will miss

[SeGaBob]

Is there any chance Karl doesn't go up and out after the stall?

No

Are you basing that on the models that are currently out of sorts? Or..?

Climatology favors it.

[SapphireSea]

I'm not buying the recurve yet for a couple of reasons.
I think the troff that is supposed to pick it up is over done. A front getting that far south is rare this time of year and troffs tend to lift out rather quickly. I dont see it dipping as far south as what the modeling says right now. Also, I dont think Karl will be as strong as the models are indicating thus a more westward direction and a system that wont feel the troff as much. We will see but the trend with some of the models has been westward. Its a wait and see. Timing will be everything on this one. If the troff gets that far south, there will be a short window to pick up Karl. If one or the other is too fast/slow they will miss

A trough does not need to dig very deeply to create a weakness that will recurve this. This is now going to be late September and the deep troughs being predicted are not completely fantasy as it would be climatologically feasible for it to happen at any time now. Interesting to note that the systems are finding instability only when it finds a weakness and begins a recurve. Food for thought.

[SouthernBreeze]

looking at extended forecast for coastal SC - no significant cool weather predicted here for several weeks

[abajan]

TROPICAL STORM KARL DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016
500 AM AST MON SEP 19 2016

Karl continues to have a rather disorganized appearance in satellite
imagery. The cloud pattern consists of a relatively small mass of
convection northeast of the center, with a separate shapeless
cluster of convection farther to the northeast. The initial
intensity estimate is held at 35 kt in accordance with the Dvorak CI
number from TAFB.

Karl's current poor structure, proximity to an upper tropospheric
low near the Lesser Antilles, and large-scale subsidence/convergence
over the tropical Atlantic suggest that the storm should only slowly
strengthen during the next couple of days. The intensity forecast
has been modified downward a bit further to reflect the likelihood
of a slower intensification. After 72 hours, a notable increase in
moisture, waters of around 30 deg C, and low shear should promote
strengthening, perhaps more than indicated in this forecast. The
intensity forecast during this time has been increased over the
previous one, and is closest to the LGEM model.

The initial motion estimate is 270/13. Karl should remain on the
south and southwest side of a subtropical ridge the next couple of
days, with the flow around this feature steering the cyclone
westward and then west-northwestward. From days 3-5, Karl will
encounter a weakness in the ridge over the west-central Atlantic,
which should cause the cyclone to turn northwestward and northward
with a substantial decrease in forward speed. The new track
forecast is nudged to the south of the previous one through 48
hours, with more emphasis put on the weaker GFS solution. The track
forecast from days 3-5 has been adjusted to the east of the previous
one, and is consistent with the expectation of stronger cyclone as
depicted in the ECWMF solution.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0900Z 18.2N 47.7W 35 KT 40 MPH
12H 19/1800Z 18.6N 49.7W 35 KT 40 MPH
24H 20/0600Z 19.1N 52.1W 40 KT 45 MPH
36H 20/1800Z 19.9N 54.6W 45 KT 50 MPH
48H 21/0600Z 21.0N 57.1W 50 KT 60 MPH
72H 22/0600Z 24.0N 62.2W 60 KT 70 MPH
96H 23/0600Z 27.0N 65.2W 75 KT 85 MPH
120H 24/0600Z 29.5N 65.7W 85 KT 100 MPH

$$
Forecaster Kimberlain

[abajan]

Looks like it could be a close call for Bermuda. Also, per the 5 AM advisory, it's expected to be a Cat 2 in 5 days time.

[Kazmit]

Bermuda might get another Gonzalo from this one, that cone is rather ominous. I hope they're preparing, this could be a significant storm for them.

[Kazmit]

I know nothing is 100% definite, ever, with these things. That being said, is the recurve as close to definite as it gets, or should I still be planning on checking supplies?

Quite definite. Every models forecasts a recurve, and this pattern is more favorable for this time of year. I wouldn't stress about it.

[GCANE]

MIMIC-TPW
http://tropic.ssec.wisc.edu/real-time/m ... /main.html

The way I read it, it looks like a large dry-air mass is circulating around Karl on the west and will soon cut off its feed from the south.

Also, Karl is approaching a UL Trough to it's west.

IMHO, little chance for Karl to intensify until it gets on the SW side of the Trough and picks back up a moisture feed.