ATL: DORIAN - Models

[Blown Away]

18z NAM... Likes Miami also...

[Kingarabian]

Early GFS coming in, looks a bit faster but not much change north or south. Trending back west with the models now?

A bit more W on this run compared to the 12z:

[FLpanhandle91]

GFS slight south with stronger ridging to its north through 36 hours. This is a shift back west I believe.

[Blown Away]

18z GFS trend.. A bit faster and SW...

[Kingarabian]

18z GFS hours 24-54:

[Blown Away]

OMG these models making me crazy...

[HurricaneFrances04]

Heading west and starting to slow down. Possibly closer in line to the Euro solution?

[tarheelprogrammer]

Trough is coming at hour 60

[TheProfessor]

The NAM is NOT a tropical model, but it may be sniffing out some things at the synoptic and mesoscale level that some of the global models aren't. One of the main features that hasn't been talked about that is greatly influencing the track of Dorian on the NAM is the upper level high at 200mb. First will look at the steering currents at the center of the storm at 84 hours on the NAM and 90 hours on the CMC and GFS.





One thing that's obvious is how weak the steering currents are for the GFS, especially for a stronger storm. The Canadian is pretty interesting because the steering over the center isn't as weak and would suggests a more westward movement(instead of the more pole-ward one on its run.) However, north and east of the storm does support a more northerly motion. It's pretty obvious on the NAM why the storm is getting steered towards the south and west. The question is, Why does the NAM do this and does it make sense? Well let me show you what's happening on the 200mb level.

We'll talk about the GFS and Canadian first.

It's pretty obvious that the storm on the GFS is being influenced by the western periphery of the 200mb ridge in the Atlantic with very little influence coming from the low to the southeast and high to the west.


The Canadian is far more interesting. Earlier when just looking at the wind profiles it would seem like the Canadian would be sending the storm west and not more northwestward. The 200mb flow reveals the answer why the storm has a more northerly motion that's also not very fast. The storm on the CMC is being influenced by the same 200mb high pressure on the GFS. But, the storm is also being influenced by the Gulf high pressure so there are conflicting currents, causing a slower motion. The Atlantic high pressure is likely stronger than the Gulf one so Dorian still mover northward, but at a much slower pace.


Now on to the NAM. I made to gif of the last run to show you what exactly is happening that sends Dorian dive bombing to the southwest. One thing to notice is the the 200mb high is further east on the 18z run so it's not giving a northerly influence to Dorian. Initially Dorian gets caught up in the southerly motion of the 200mb high in the Gulf, which speeds Dorian up a bit and moving him southwestward. The high pressure begins to move westward reducing its influence on Dorian, however, Dorian moves so far south that Dorian is now feeling an influence from the 200mb low to its southeast. This causes Dorian to keep a southwestward motion until at least hour 84.

In my opinion there's still a lot of uncertainty with Dorian and his future track could very well depend on his exact strength and whether or not he taps into the 300 and 200mb steering flows. Where these lows and highs set up will be critical, both intensity and track wise.

[Kingarabian]

12z GFS 500mb heights trend of the past 4 runs:

[Kingarabian]

18z GFS hour 48-72:

[MrJames]

Legacy GFS slightly south and slowing down as it nears WPB.

[PavelGaborik10]

Looks like it's going to miss Florida. Wow.

Edit : the 18z GFS run that is.

[Craters]

https://i.imgur.com/a9SfVT2.gif
18z ICON... Likes Miami...

...or doesn't.

[La Sirena]

https://i.imgur.com/Ey32gWc.gif
18z NAM... Likes Miami also...

That’s showing a definitive WSW dip!

[Siker]

Yeah less ridging and a stronger shortwave out west than the Euro on this run. Would be surprised if hits Florida on this specific run.

[jfk08c]

Looks like it's going to miss Florida. Wow.

Edit : the 18z GFS run that is.

If you look at the previous run, it had the same slowdown but eventually continued NNW into the state. Don't write it off just yet

[beachman80]

There’s the jump north on the 18z gfs.
Here comes the turn.

Edit: and then straightens out.

[Kingarabian]

18z GFS still moving west between hours 72-78.

[BobHarlem]

South jog at 84 on the GFS.