ATL: GERT - Post-Tropical - Discussion

[chaser1]

interesting..

[img]https://www.nrlmry.navy.mil/htdocs_dyn_apache/PUBLIC/tc_pages/thumbs/medium/tc17/ATL/99L.INVEST/amsub/89/2degreeticks/20170809.0708.noaa19.x.89.99LINVEST.25kts-1012mb-165N-545W.100pc.jpg[img]

Pretty clear there is a small closed circ..

[img]https://www.nrlmry.navy.mil/tcdat/tc17/ATL/99L.INVEST/tc_ssmis/91h/2degreeticks/20170809.0714.f16.x.91h.99LINVEST.25kts-1012mb-165N-545W.62pc.jpg[/ig]

Wonder how long it'll hold with models beginning to back off.

Certainly does look closed... although I want to point out that we had systems in the Epac with defined LLCs on microwave imagery yet the NHC would not classify them until later if ever.

"Models be damned". I'm guessing it'll hold if conditions are becoming (and remain) more favorable lol. Of course, like any other meso-scale feature this is that much more fragile and subject to more rapid changes. As for the models, if 99L persists then they'll eventually come around.

[chaser1]

00z Euro trended much weaker, probably was way overdoing the intensity on this so now it is closer to the GFS. Chances this strikes the U.S. are slim now in my opinion.

Doesn't that seem like a contradiction? I think it stands to reason that a stronger (prior EURO run) system would be more apt to move more poleward. So now, we seem to have the EURO backing off and i would think that the GFS would be carrying a far more shallow low level feature, further west??

Theoretically, then you have the other dynamic of a possibly smaller tropical cyclone that could suggest a possibility of its motion being more influenced by smaller (more localized) steering conditions as well.

[tolakram]

The lower level steering favors a recurve as well.

http://tropic.ssec.wisc.edu/real-time/dlmmain.php?&basin=atlantic&sat=wg8&prod=dlm1&zoom=&time=

[tolakram]

Even if you give the Euro a 60% share of the blend I think we're looking at a very weak tropical storm or no development.

Euro - weak
GFS - Nada
Navgem - Nada
CMC - Hypercane

The posts in this forum are NOT official forecasts 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 NHC and NWS.

[NDG]

Looking at hr vis satellite loop hard to tell a well defined surface LLC but there does appear to a closed small vorticity just above the surface, gaining some latitude this morning. Fighting some moderate to strong NW shear.

[abajan]

The TWO is late.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Wed Aug 9 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical
Storm Franklin, located over the Bay of Campeche.

Shower activity has increased a little this morning in association
with a trough of low pressure located about 400 miles east of the
Leeward Islands. Significant development of this system is not
expected during the next couple of days due to unfavorable
environmental conditions. However, conditions are forecast to
become somewhat conducive for development of this system late this
week and this weekend while it moves west-northwestward
to northwestward over the western Atlantic.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...40 percent.

$$
Forecaster Cangialosi

[abajan]

[chaser1]

The lower level steering favors a recurve as well.

http://tropic.ssec.wisc.edu/real-time/dlmmain.php?&basin=atlantic&sat=wg8&prod=dlm1&zoom=&time=

I disagree. If that's an analysis map, then I can't see how any shallow system south of 20N (and east of 65W), would have a motion north of 280º in the near term and given its potentially westward convective position. Now, if that were the forecast map for say 48-72 hours and it verified, we'll than I'd have to agree.

[Blown Away]

Still WNW.

[cycloneye]

12z Best Track:

AL, 99, 2017080912, , BEST, 0, 171N, 557W, 25, 1012, DB

[Steve]

Even if you give the Euro a 60% share of the blend I think we're looking at a very weak tropical storm or no development.

Euro - weak
GFS - Nada
Navgem - Nada
CMC - Hypercane

The posts in this forum are NOT official forecasts 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 NHC and NWS.

I don't know. This is a tough one because obviously there are factors the globals are considering. It's a high risk play to ever bet on the CMC when it's an outlier model. But I wouldn't write this off yet just based on the pattern. It definitely looks like a recurve based on the upstream weather on and coming off the continent. I'd give it a 50/50 shot at a name.

[tolakram]

The lower level steering favors a recurve as well.

http://tropic.ssec.wisc.edu/real-time/dlmmain.php?&basin=atlantic&sat=wg8&prod=dlm1&zoom=&time=

I disagree. If that's an analysis map, then I can't see how any shallow system south of 20N (and east of 65W), would have a motion north of 280º in the near term and given its potentially westward convective position. Now, if that were the forecast map for say 48-72 hours and it verified, we'll than I'd have to agree.

That's current, not a forecast. I see low levels winds rounding the high pressure so that even a tiny disturbance will tend to rotate around it. I don't know what it will look like in 3 days though

[cycloneye]

 https://twitter.com/BigJoeBastardi/status/895278528446517248

[Aric Dunn]

its looking better. still sustained convection with some new convection building north of the center. pretty easy to see the circ right at the edge of the convection partially covered.

[weathaguyry]

99L really not looking bad right now, conditions are also improving for it to strengthen, it should be making a NW jump soon like the models were showing, but it still looks to be moving WNW, so if it doesn't make that jump, the track may have to be adjusted accordingly.

[weathaguyry]

Euro has it at 21N/ 61W at 8PM tomorrow night, so we will see what happens

[Blown Away]

12z Best Track:
AL, 99, 2017080912, , BEST, 0, 171N, 557W, 25, 1012, DB

Clearly the low being tracked is in the southern lobe of the convection near 17.5N/56.5W... That circulation is powering to the WNW with no indications of making a sudden NW turn...

 https://twitter.com/BigJoeBastardi/status/895278528446517248

Seems the models are hinting at the center consolidating much farther N between the 2 convective blobs. I think that is what the models are trying to show, may just be center relocation rather than our current low suddenly moving NW.

[Steve]

I'd agree with that. Per his morning video, there's more vorticity higher up in the atmosphere with 99L. It's also entangled with an Upper Level Low to its north and dry air coming down from the NW. If the ULL pulls away, and the center consolidates a bit farther north, I think you have pattern reversal and the possibility of an anti-cyclone building overhead in a few days. It's still just something to watch and doesn't appear as if it will be a US threat, but it might still be close.

[gatorcane]

12Z GFS says nothing to look at move on - insists no development.