Strong Tropical Wave to emerge from West Africa today (Is Invest 95L)

[LarryWx]

The 6z run continues to show how inept the GFS is at modeling tropical waves in the eastern Atlantic. Just like with Larry’s precursor, it has this wave interact with other areas of vorticity and get spun around/ripped apart. The Euro has done a far better job sniffing out MDR genesis so far this year, quite a change from its abysmal performance in 2020.

Speaking of the Euro, that 00z run would probably lead to a 120-130 kt Cat 4 with all the 29.5-30C waters it’ll be going over.

The Euro was absolutely abysmal with the wave that came off Friday. It had a sharply recurving TS+ on run after run vs the GFS, which always kept it a non-recurving weak low which is what has verified.

[Ulster]

I’ve never seen a Korean model posted before. I wonder if it’s a standalone or if it uses a parent model.

It leans on the Unified Model from the UK Met Office.

[LarryWx]

12Z UKMET: has genesis at hour 60 but keeps it weak/moving WNW and then it dissipates:



NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 54 HOURS
FORECAST POSITION AT T+ 54 : 11.9N 20.6W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 15.09.2021 60 12.2N 22.3W 1010 29
1200UTC 15.09.2021 72 12.5N 26.3W 1010 30
0000UTC 16.09.2021 84 13.3N 30.0W 1012 29
1200UTC 16.09.2021 96 14.2N 34.1W 1013 29
0000UTC 17.09.2021 108 CEASED TRACKING

[LarryWx]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago and was frankly surprised. That is an example where knowing climo is helpful.

[aspen]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago.

Seems like the Bahamas AOI, both as a TC and a post-tropical low, open up a gap in the ridge that the hurricane takes advantage of. This is on the far eastern side of the range of tracks other models show, however.

The GFS is still garbage at modeling AEWs and splits this apart yet again. We’ll have to wait for the ensembles to see if the 12z guidance is seeing an east shift.

[gatorcane]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago and was frankly surprised.

[LarryWx]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago.

Seems like the Bahamas AOI, both as a TC and a post-tropical low, open up a gap in the ridge that the hurricane takes advantage of. This is on the far eastern side of the range of tracks other models show, however.

The GFS is still garbage at modeling AEWs and splits this apart yet again. We’ll have to wait for the ensembles to see if the 12z guidance is seeing an east shift.

But as mentioned, the GFS did very well with the wave currently in the eastern Atlantic as it always kept it weak vs the Euro, UKMET, and ICON, which all had many runs of TS+.

[gatorcane]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago.

Seems like the Bahamas AOI, both as a TC and a post-tropical low, open up a gap in the ridge that the hurricane takes advantage of. This is on the far eastern side of the range of tracks other models show, however.

The GFS is still garbage at modeling AEWs and splits this apart yet again. We’ll have to wait for the ensembles to see if the 12z guidance is seeing an east shift.

But as mentioned, the GFS did very well with the wave currently in the eastern Atlantic as it always kept it weak vs the Euro, UKMET, and ICON, which all had many runs of TS+.

Here is the 12Z GFS from 120 hour animation. Look at that trough over the Azores which looks to really slow the progress westward of this wave. Very fall-like progressive pattern on the GFS.

[gatorcane]

It is notable that the CMC has trended weaker from yesterday’s runs but not quite as weak as the GFS. Also has trended more north. Looks like

[LarryWx]

The 12Z ICON has this become a H that turns NNW by 45W up already to 20N (as a cat 2),which would have almost definitely meant never getting close to the SE US based on history even allowing for a more W movement for a period later on. I haven’t found even one storm on record back to 1851 moving NW to NNW that far east in the MDR able to come back to the US. I did that research several years ago and was frankly surprised.

https://i.postimg.cc/Rh4hw9yM/icon-mslp-pcpn-eatl-fh60-180.gif

Looking like it now per model consensus, especially if it becomes strong early but still too early imo to make a confident call as it is still over Africa. Lots can still change as a few EPS members have shown and also if it stays weak quite far west.

[LarryWx]

The 12Z GEFS once again has many geneses but it also looks very fishy.

[cycloneye]

Another tropical wave is forecast to move off the west coast of
Africa on Monday. Gradual development of this system is possible
thereafter, and a tropical depression could form by the middle of
the week while it moves westward across the eastern tropical
Atlantic Ocean.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...medium...60 percent.

[Blown Away]

The 12Z GEFS once again has many geneses but it also looks very fishy.

Huge spread from day 7-10, which should be expected, but there are a number of ensembles that shifted SW. Certainly not a slam dunk fish ATM.

[AutoPenalti]

I’ve never seen a Korean model posted before. I wonder if it’s a standalone or if it uses a parent model.

It leans on the Unified Model from the UK Met Office.

That’s pretty cool, Is there documentation on how it operates?

[LarryWx]

The 12Z GEFS once again has many geneses but it also looks very fishy.

Huge spread from day 7-10, which should be expected, but there are a number of ensembles that shifted SW. Certainly not a slam dunk fish ATM.

With it still being over Africa and with such a complex setup, it most certainly isn’t a slam dunk miss of the Conus even though that is favored. It would still be two weeks away if it were to hit.

[Category5Kaiju]

What I am trying to figure out is the reason why models want it to recurve; is it the Bahamas AOI that causes a breach in the ridge? Or is Chanthu not doing enough to enhance the Canadian ridge? Or is it something else entirely? Either way, one part of me still wants to keep an eye on this storm as it definitely does not look as OTS-definitive as Larry did in its formative stages, and I still remember that graphic Eric Webb posted in July or so about ASO having an anomalously high level of Canadian ridging.

[SFLcane]

And we’re is the tc on the 12z euro? Totally different upper air pattern also

[gatorcane]

About face on the Euro. Totally drops it through 96 hours so far. Looks like the GFS may have been right all along

[Ulster]

I’ve never seen a Korean model posted before. I wonder if it’s a standalone or if it uses a parent model.

It leans on the Unified Model from the UK Met Office.

That’s pretty cool, Is there documentation on how it operates?

I think if you google KMA and KIM you can find some papers on it. I am in the supercomputer business so I only know core dependencies but not underlying details.

[Stormybajan]

Andddd...the 12z euro has some strungout energy. Such a massive change from what it had before. It wouldnt be a good look for the euro if this doesnt become a strong system after being so consistent. Especially being completely wrong about 93L also ..lets see what happens after 96 hours in this run..not expecting much