ATL: GERT - Post-Tropical - Discussion

[chaser1]

As a point of interest, I've been warily keeping an eye on this wave in the Bahamas preceding 99L and it's steady WNW motion. Unlikely to suddenly spin up, i believe this shallow to mid level feature has been able to primarily slide further west in part becsuse it is not a deeper vertically stacked system and given its latitude might then justify a more NW motion as the EURO had been suggesting 99L might soon take. Point is, if 99L continues on a more 275-285 heading in the near term and continue to pulsate but not quite sustain deep convection for at least 48 hours or more, then I could see an increased threat of mid term genesis occurring further west than the EURO is projecting and a risk of a closer in spin up that might then be oriented to far south and west to necessarily swing east of the CONUS. I definitely believe it's one to keep a close eye on.

[chaser1]

Weaker could mean "no developmrnt" but it could also mean a near term primarily low level feature that moves further west with shallow low level trades. Downstream implications range from zero, to the potential of a further west and south forming tropical cyclone that may then pose a greater threat to the Bahamas and points along the US Coastline then present models suggest

[northjaxpro]

I agree. The southern vorticity is in the process I believe of taking over as the primary one. The system I believe could be re-initialized as far as 400-500 miles to the south and west . This could have potential major implications down the pike for sure.

[Hammy]

I agree. The southern vorticity is in the process I believe of taking over as the primary one. The system I believe could be re-initialized as far as 400-500 miles to the south and west . This could have potential major implications down the pike for sure.

Could this be the cause of the Euro run being weaker (and the GFS not developing), essentially initializing the wrong end of the wave?

[Digital-TC-Chaser]

[quote="Kingarabian"]00z Euro coming in weaker compared to the past two runs. 72hrs:

72hrs is is a good forecast time the way the models are atm.

weaker storm also off SE.
http://www.pivotalweather.com/model.php ... watl&dpdt=

[northjaxpro]

I agree. The southern vorticity is in the process I believe of taking over as the primary one. The system I believe could be re-initialized as far as 400-500 miles to the south and west . This could have potential major implications down the pike for sure.

Could this be the cause of the Euro run being weaker (and the GFS not developing), essentially initializing the wrong end of the wave?

I really think this has been a real possibility all along. We should get a better idea hopefully about this within the next 24 hours or so.

[chaser1]

Okay, this is weird?? We've all probably heard the expression "a sucker hole", with regards to one incorrectly attributing a certain (cloud or other) feature as being the center of a tropical cyclone, right? So check this one out.....

http://www.ssd.noaa.gov/PS/TROP/floater ... 0-lalo.gif

I found this rather odd and it shows up now (As of the time of this post) for 99L on both the Vid. & RGB satellite resolution. Oddly, I expected this feature to be some reflection of water vapor but it doesn't show up on that resolution. I hope someone else is up and watching so that this might be recorded as a loop.

[chaser1]

I'm not sure if my last post above was entirely clear. Look at the large "eye feature" that appears at first light just south of the more northern area of convection associated with 99L.
http://www.ssd.noaa.gov/PS/TROP/floater ... 0-lalo.gif

[Aric Dunn]

I think they might want to up the chances from zero.. to at least 50 percent for that southern area of convection.

[chaser1]

I think they might want to up the chances from zero.. to at least 50 percent for that southern area of convection.

Yep, I was thinking the very same thing. Even if they'd prefer to err on the side of caution, I'd certainly up it to 20% within 48 hours (and in a hurry). I'd probably go with 30% within 48 hr's, and 50% within 5 days but I'd even consider that as rather conservative

[Aric Dunn]

I think they might want to up the chances from zero.. to at least 50 percent for that southern area of convection.

Yep, I was thinking the very same thing. Even if they'd prefer to err on the side of caution, I'd certainly up it to 20% within 48 hours (and in a hurry). I'd probably go with 30% within 48 hr's, and 50% within 5 days but I'd even consider that as rather conservative

Yeah there was clearly a circualtion yesterday before sunset just limited convection.. the convection is still not all too organized but has been persistant arounf that circ for about 12 hours now. There is some wswwinds at least looking at early visible.

[TheStormExpert]

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.

[Aric Dunn]

interesting..



Pretty clear there is a small closed circ..

[Nimbus]

I only saw the southern vort last night, and the convection this morning will probably keep that alive.
Not sure if its a good thing or not, although it would tend to limit development further north it might become the primary center and change the models.

[chaser1]

I'm just wondering if it's more of a transient feature; such as being one of multiple competing areas of vorticity? Overall though, my guess is that this is the more dominant cyclonic feature but perhaps a tighter reflection of about the mid to 850mb levels, and maybe only now just getting closer to working its way down to the surface?

[chaser1]

I only saw the southern vort last night, and the convection this morning will probably keep that alive.
Not sure if its a good thing or not, although it would tend to limit development further north it might become the primary center and change the models.

One thing to consider..... if in fact this were to become the dominant feature, it's apparent small & tight COC would certainly NOT be good news for the Leeward & Virgin islands given these two factors:
1) increased oceanic water temps
2) the potential for faster deepening given its small size

[Kingarabian]

00z EPS less bullish.

[SFLcane]

Some 06z models turning this abruptly wnw-nw rather quickly now away from the SE.

[Kingarabian]

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.

[chaser1]

There it is! I'm hearing it in my head again
Someone key up that song, Bad Moon Rising!!