2019 Tropics: Global Model Runs Discussion (Out to day 16)

[USTropics]

https://twitter.com/yconsor/status/1154725388758765568

Something to note.. for the first time this summer there is a large wave over africa that is farther north spreading rain over the southern Saharah region ( the Sahel region I believe) where most fo the SAL that affects the deeps tropics comes from. It receives rain each spring and summer, but this year up till now has been particularly dry which is why we have seen a rather large uptick in the SAL outbreaks this July in the eastern Atlantic.

Here's a great image of that (which should also help protect the AEW to the south that the ECMWF is starting to develop). Seen this a few times, where a leading wave to the north becomes a sacrificial lamb, providing a barrier from dry air entrainment in the AEW to the south (which you can see the dry air beginning to affect the waves in CATL and off Africa).

[Aric Dunn]

https://twitter.com/yconsor/status/1154725388758765568

Something to note.. for the first time this summer there is a large wave over africa that is farther north spreading rain over the southern Saharah region ( the Sahel region I believe) where most fo the SAL that affects the deeps tropics comes from. It receives rain each spring and summer, but this year up till now has been particularly dry which is why we have seen a rather large uptick in the SAL outbreaks this July in the eastern Atlantic.

Here's a great image of that (which should also help protect the AEW to the south that the ECMWF is starting to develop). Seen this a few times, where a leading wave to the north becomes a sacrificial lamb, providing a barrier from dry air entrainment in the AEW to the south (which you can see the dry air beginning to affect the waves in CATL and off Africa).

https://i.imgur.com/beKI2tN.jpg

yeah that wave essentially travelled east to west giving the Bodélé Depression ( region of the Sahel where pretty all the SAL comes from) area some rain. Will see what happens over the next couple weeks ... to see if the waves spread more moisture north now.

[Siker]

12z ICON merges the two waves out in the central Atlantic right now, spinning up a TC south of Bermuda in a week. 12z GFS keeps the waves separate and energy is thus diffuse.

[Aric Dunn]

12z GFS much more vigorous with the wave the EURO develops. lets see what happens..

[AutoPenalti]

Are we designating any of these waves into Pouches?

[USTropics]

Are we designating any of these waves into Pouches?

Manual pouch tracking was terminated after 2016, I believe there is a site that has automated this process some (not perfect, I'll see if I can find the link later).

[Aric Dunn]

Are we designating any of these waves into Pouches?

Manual pouch tracking was terminated after 2016, I believe there is a site that has automated this process some (not perfect, I'll see if I can find the link later).

you have these people tracking the waves.. lol

https://ttweathercenter.com/category/tropical-update

and no development from Euro on the 12z.

[AnnularCane]

What's the difference between a wave and a pouch anyway?

[floridasun78]

What's the difference between a wave and a pouch anyway?

pouch are area could start too show up on models runs soon wave are area of storms moving alone tropical from east to west

[USTropics]

What's the difference between a wave and a pouch anyway?

There isn't really a difference, pouch was designated because of the immediate environment that the wave axis exists in. Essentially the pouch acted as a safeguard for the seed of vorticity, protecting from negative conditions like dry air entrainment (fun fact, 'pouch' term was coined from the kangaroo pouch that holds their newborns). There's actually a scientific article that details this. It's common to also call them AEWs (African Easterly Waves) or just simply waves. You'll also see convectively stripped waves that maintain a sharp axis labeled as 'dry waves', essentially traversing most of the Atlantic before finding favorable conditions further west.

[gatorcane]

It’s interesting to note the GFS legacy shows a much more convectively active wave rolling off Africa in 96 hours than the new GFS (I say interesting because personally I think the upgraded GFS is even more conservative with predicting genesis than the old GFS which was already on the conservative side). Additionally the Euro looks more closely aligned to the legacy GFS on the 850mb vort signature as it traverses the MDR. Wouldn’t surprise me if the NHC mentions this wave in an upcoming update - possibly a brief spin-up here is possible:

[floridasun78]

It’s interesting to note the GFS legacy shows a much more convectively active wave rolling off Africa in 96 hours than the new GFS (I say interesting because personally I think the upgraded GFS is even more conservative with predicting genesis than the old GFS which was already on the conservative side). Additionally the Euro looks more closely aligned to the legacy GFS on the 850mb vort signature as it traverses the MDR. Wouldn’t surprise me if the NHC mentions this wave in an upcoming update - possibly a brief spin-up here is possible:

https://i.postimg.cc/9FKd7Fft/gfs-legacy-ir-atl-17.png

likely next week it early if do maybe by next tue or so

[Hammy]

All quiet for the next two weeks on the latest batch of models. You know things are dead when even the Canadian can't find anything to spin up.

[jlauderdal]

It’s interesting to note the GFS legacy shows a much more convectively active wave rolling off Africa in 96 hours than the new GFS (I say interesting because personally I think the upgraded GFS is even more conservative with predicting genesis than the old GFS which was already on the conservative side). Additionally the Euro looks more closely aligned to the legacy GFS on the 850mb vort signature as it traverses the MDR. Wouldn’t surprise me if the NHC mentions this wave in an upcoming update - possibly a brief spin-up here is possible:

https://i.postimg.cc/9FKd7Fft/gfs-legacy-ir-atl-17.png

The old GFS was conservative with genesis?

[NotSparta]

All quiet for the next two weeks on the latest batch of models. You know things are dead when even the Canadian can't find anything to spin up.

Didn't the Canadian get updated to not show as many ghost storms?

[crownweather]

All quiet for the next two weeks on the latest batch of models. You know things are dead when even the Canadian can't find anything to spin up.

Pssst....take a look at the 00Z ICON.

[USTropics]

00z UKMET has the same system developing from the wave currently just east of the Leeward Islands:

[crownweather]

00z UKMET has the same system developing from the wave currently just east of the Leeward Islands:

https://i.imgur.com/Kdv7uec.png

That's interesting. I'm really starting to wonder if the FV3-GFS and Euro models may have been tweaked a little too much towards not showing anything until "game time".

[USTropics]

NCEP ensembles continue to show about a 40% chance of development from this wave:

[USTropics]

00z UKMET has the same system developing from the wave currently just east of the Leeward Islands:

https://i.imgur.com/Kdv7uec.png

That's interesting. I'm really starting to wonder if the FV3-GFS and Euro models may have been tweaked a little too much towards not showing anything until "game time".

While the operational runs don't show development, there is support from some of the ensemble guidance from the GFS:


The same is true for the ECMWF ensembles: