ATL: GONZALO - Remnants - Discussion

[EquusStorm]

Some really beefy bands getting going in those last few frames. Pretty impressive.

[Aric Dunn]

This is about to explode..

[Shell Mound]

The NHC is probably conservative because the system is clearly tilted due to easterly shear and the convective pattern has been generally “bursting” rather than consolidating. The latest IR isn’t terribly impressive, though the system is clearly holding its own through the diurnal minimum. Personally, I think some people tend to presume a system is more organised than it actually is. As of now this is a borderline TD, not a clear-cut case. One can make a 50/50 case for either an upgrade or retention. Perhaps the NHC is awaiting one more diurnal maximum before “pulling the trigger.” Honestly, I don’t have a problem with the NHC’s meteorological reasoning at this time.

[cainjamin]

Structure has definitely improved with more and more spiral banding. Convection isn't very deep at this point though. It will be really interesting to see what happens with DMAX overnight - if 99L can build a CDO tonight then the HWRF forecast becomes a little more reasonable. I think the best bet intensity-wise is still a moderate TS when it reaches the islands.

[Shell Mound]

Structure has definitely improved with more and more spiral banding. Convection isn't very deep at this point though. It will be really interesting to see what happens with DMAX overnight - if 99L can build a CDO tonight then the HWRF forecast becomes a little more reasonable. I think the best bet intensity-wise is still a moderate TS when it reaches the islands.

Personally, I think the HWRF is far too aggressive. In most of these cases the ECMWF and/or the GFS tend to be more accurate, as they were with Erika ‘15. The HWRF, if I recall correctly, was consistently bullish with Erika while the EC/GFS correctly expected dissipation earlier than the NHC’s consensus-weighted forecast(s) anticipated. While the system could exceed expectations in the short term, increasing shear and SAL will overtake the system before it reaches the islands, so rapid degeneration by then is probable. One can already see that the HWRF is busting, since it presupposed faster organisation by now than is actually taking place. The convective scheme likely exaggerates vertical lift and convective processes.

 https://twitter.com/webberweather/status/1285626421763874817

[GCANE]

A fast rising tower is popping up.
The updraft should create some good helicity and get the LL vort spinning up.

[TheProfessor]

Structure has definitely improved with more and more spiral banding. Convection isn't very deep at this point though. It will be really interesting to see what happens with DMAX overnight - if 99L can build a CDO tonight then the HWRF forecast becomes a little more reasonable. I think the best bet intensity-wise is still a moderate TS when it reaches the islands.

Personally, I think the HWRF is far too aggressive. In most of these cases the ECMWF and/or the GFS tend to be more accurate, as they were with Erika ‘15. The HWRF, if I recall correctly, was consistently bullish with Erika while the EC/GFS correctly expected dissipation earlier than the NHC’s consensus-weighted forecast(s) anticipated. While the system could exceed expectations in the short term, increasing shear and SAL will overtake the system before it reaches the islands, so rapid degeneration by then is probable. One can already see that the HWRF is busting, since it presupposed faster organisation by now than is actually taking place. The convective scheme likely exaggerates vertical lift and convective processes.

The HWRF is typically over aggressive, however it does do well with these small storms like Danny 2015. If dry air were the only obstacle with 99L I'd be more inclined to believe a hurricane could be possible, however with the current background state of the atmosphere being somewhat unfavorable in general I do think it's less likely the HWRF is right with this one. However if 99L can continue to produce convection and stay in a moisture pocket there's no reason why it can't become a hurricane while shear is low.

[Aric Dunn]

Big ole hot tower developing on the east side of the center wraping around.. these pulsing hot towers are incredibly normal and are increasing the mid level vorticity..

this latest one looks to set off some pretty explosive convection.

[northjaxpro]

Structure has definitely improved with more and more spiral banding. Convection isn't very deep at this point though. It will be really interesting to see what happens with DMAX overnight - if 99L can build a CDO tonight then the HWRF forecast becomes a little more reasonable. I think the best bet intensity-wise is still a moderate TS when it reaches the islands.

Personally, I think the HWRF is far too aggressive. In most of these cases the ECMWF and/or the GFS tend to be more accurate, as they were with Erika ‘15. The HWRF, if I recall correctly, was consistently bullish with Erika while the EC/GFS correctly expected dissipation earlier than the NHC’s consensus-weighted forecast(s) anticipated. While the system could exceed expectations in the short term, increasing shear and SAL will overtake the system before it reaches the islands, so rapid degeneration by then is probable. One can already see that the HWRF is busting, since it presupposed faster organisation by now than is actually taking place. The convective scheme likely exaggerates vertical lift and convective processes.

The HWRF is typically over aggressive, however it does do well with these small storms like Danny 2015. If dry air were the only obstacle with 99L I'd be more inclined to believe a hurricane could be possible, however with the current background state of the atmosphere being somewhat unfavorable in general I do think it's less likely the HWRF is right with this one. However if 99L can continue to produce convection and stay in a moisture pocket there's no reason why it can't become a hurricane while shear is low.

Precisely Professor. I always refer to Hurricane Danny in 2015 as well. I have already referred to it several times this season due to several small vorts developing this year, especially Edouard and Fay.

These small vorts like Danny in 2015 can create their own unique envionments,and are quute difficult for the reliable models to analyze them. Danny had only one model (HWRF) at the time to even develop it. It went on to become a major Cat 3 hurricane, albeit one of the smallest cyclones I can ever recall tracking and analyzing. Definitely among my all -time favorite cyclones through the years.

[TheStormExpert]

Why doesn’t the NHC issue Potential Tropical Cyclone advisories anymore? I really don’t see the point of them releasing that option back in 2017 if they’re not going to efficiently take advantage of that option anymore.

[Aric Dunn]

[Extratropical94]

Why doesn’t the NHC issue Potential Tropical Cyclone advisories anymore? I really don’t see the point of them releasing that option back in 2017 if they’re not going to efficiently take advantage of that option anymore.

Probably because the system doesn't pose a threat to any land areas in the next 48 hours.

[EquusStorm]

I think the PTC designation is mostly for storms that have land impact of some sort within 48 hours or so but they haven't used them that often lately even when that's the case

[GCANE]

Big ole hot tower developing on the east side of the center wraping around.. these pulsing hot towers are incredibly normal and are increasing the mid level vorticity..

this latest one looks to set off some pretty explosive convection.

This one is not washing out so fast.
Actually, cloud tops are getting colder.

[drezee]

https://i.ibb.co/JFPQ6sc/5555.gif

Boomer going off. TS by 03z

[Cataegis96]

 https://twitter.com/TropicalTidbits/status/1285656782191370242




New Levi video soon. Certainly some portentous wording there. We may look back to this week as the beginning of when things started to take off when the 2020 season is all said and done.

[Aric Dunn]

Big ole hot tower developing on the east side of the center wraping around.. these pulsing hot towers are incredibly normal and are increasing the mid level vorticity..

this latest one looks to set off some pretty explosive convection.

This one is not washing out so fast.
Actually, cloud tops are getting colder.

Yeah, there were a bunch of smaller towers today and a few finally were able to wrap around a few hours ago and close off the moisture loop. I knew this was coming.


and it is on the Se/E side.. very indicative..

[tarheelprogrammer]

I believe this is now a low-end TS. I think this could surprise the Leewards.

[ouragans]

Why doesn’t the NHC issue Potential Tropical Cyclone advisories anymore? I really don’t see the point of them releasing that option back in 2017 if they’re not going to efficiently take advantage of that option anymore.

PTC is when a system is 48 hrs or less from land with watches/warnings need to be issued for that territory. 99L is too far from the islands

[tiger_deF]

I've seen way more speculation about the wave behind 99L than 99L itself but tbh I think that this has a chance to be an immediate threat to the windward islands. While it will be fighting some drier air, not only will a stronger stacked system be more resilient to dry air, but SST's are running well above average ahead of it, and we could see a real threat to the Antilles and maybe even the CONUS.