ATL: IDA - Models

[Clearcloudz]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

[South Texas Storms]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

https://i.imgur.com/yrndd8x.png

Yeah it's interesting that the 0z GFS Ensemble doesnt have an eastward shift to the mean compared to the past few runs. That tells me that additional shifts back west are probable.

[IcyTundra]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

https://i.imgur.com/yrndd8x.png

Operational runs are going to have wild swings west and east until a center consolidates which probably won't happen until Friday or early Saturday. The ensembles are good to get a good range of possibilities of where it could go.

[Shell Mound]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

https://i.imgur.com/yrndd8x.png

Operational runs are going to have wild swings west and east until a center consolidates which probably won't happen until Friday or early Saturday. The ensembles are good to get a good range of possibilities of where it could go.

At this point I think that anywhere between Port Isabel and Velasco, TX, is at greatest risk of potential impacts, given that future W corrections are likely.

[catskillfire51]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

https://i.imgur.com/yrndd8x.png

Operational runs are going to have wild swings west and east until a center consolidates which probably won't happen until Friday or early Saturday. The ensembles are good to get a good range of possibilities of where it could go.

At this point I think that anywhere between Port Isabel and Velasco, TX, is at greatest risk of potential impacts, given that future W corrections are likely.

There is no velasco, tx, I think you mean Freeport, Tx. You don't think it will get any further east then that?

[ROCK]

Mexico to Louisiana. We might start seeing shifts back west in future cycles on the operational runs.

https://i.imgur.com/yrndd8x.png

Yeah it's interesting that the 0z GFS Ensemble doesnt have an eastward shift to the mean compared to the past few runs. That tells me that additional shifts back west are probable.

Correct…I wouldn’t get too hung up on any one model run this far out lol we don’t have a COC yet.

[IcyTundra]

[CrazyC83]

One thing is for sure: the range of possibilities stretches from Veracruz City to Apalachicola. There's still a great deal of uncertainty.

They are so bullish on intensity...would a stronger storm be favored to go north more?

[Keldeo1997]

[IcyTundra]

HWRF doing typical HWRF things. I do think the HWRF develops this way too quickly as it has 99L becoming a TS by tomorrow evening. Also skeptical that it will get that far north in the Carribean as it showing it passing over the western tip of Cuba. HWRF also has a northern bias just some things to keep in mind.

[kevin]

https://www.tropicaltidbits.com/analysis/models/hwrf/2021082500/hwrf_mslp_wind_99L_43.png

HWRF is going full HWRF mode, except this time I wouldn't be too surprised if something like this actually verifies considering how aggressive the other models are as well.

[IcyTundra]

00Z Euro TX/LA border 991 MB. A shift west from the 12Z Euro which showed a Vermillion Bay landfall in Central LA.

[SoupBone]

00Z Euro TX/LA border 991 MB. A shift west from the 12Z Euro which showed a Vermillion Bay landfall in Central LA.

It's actually about 30 or so miles east of the TX/LA line, but yeah it's very close to the GFS and CMC now. And apparently the HWRF.

[CYCLONE MIKE]

Some are making this more complicated than it is. For starters the ridge is forecast by all models to be weaker than a couple of days ago with a much stronger system meaning it will move more north. Add the fact the models right now are showing this consolidating in the central Caribbean and shooting the Yucatan channel gap versus deep down by Central America and crossing the Yucatan, like the gfs was originally showing, also leads to a storm that will move into the more northern portion of the gulf. Now that being said it could form further south and cross over the Yucatan and we throw all these runs out the window and be back at square one with a Deep South texas or Mexico threat again. IMO where it forms and if it shoots the gap will be the biggest determining factor of a northern gulf coast hit. Of course the stronger it is the more north it goes as well. I’m not liking the fact the gfs is coming East though. The other gulf storms ended up more East than forecast except for Grace but that was cut and dry due to strength of the ridge.

[grapealcoholic]

Euro 0z

[Keldeo1997]

Well hello there

[USTropics]

The evolution in the short-term will have a significant impact on the eventual track and future impacts on the CONUS from 99L. We currently have two area of vorticity in the Caribbean, a topographically enhanced vortex streamer in the SE Caribbean by Columbia (circled in white—these are referenced as forced vortices, a result of the geographical curvature and mountainous topography of Columbia/Panama, which often causes erroneous ensemble trackers from the GEFS output). In addition, we have a tropical wave currently entering the central Caribbean (wave axis highlighted in pink). The result of this will be a central pivotal point, where the low-level energy associated with the tropical wave will be pivoted to the NW around the flow of the vortex circled in white (this eventual track is also highlighted in pink):


We can see this process already occurring over the past 12 hours:


As this evolution occurs, and the tropical wave axis becomes tilted from the NW-SE due to the enhanced trade flow over the Caribbean (currently slightly tilted from NE to SW as it enters the central Caribbean), the most likely area for consolidation will be in the NW Caribbean. The current 0z GFS forecast shows this, with consolidation off the NE tip of the Yucatan peninsula over the Yucatan Channel:


There is one caveat to this though. If the NW lobe does not extend far enough north or does not consolidate quickly, we could see another central pivot point that drags the southern lobe to the north. This would delay organization and initialization would be more to the south, as seen in the 18z GFS forecast:


Once we clear this hurdle, steering influence will be dictated by the pattern over the United States. There is currently a high pressure area centered over the Great Lakes that extends down to the SE CONUS and into the EGOM. In addition, there is a shortwave trough that originates over the NW CONUS and propagates eastward over the northern states. We can see these 2 players in the 4 day forecast of the 00z GFS model:


The timing and orientation of this shortwave trough will be critical to the future track of 99L once it reaches the GOM. The GFS trend over the past 6 runs have been for a more progressive trough that propagates quicker to the east. This acts to erode the western periphery of the high pressure area to its east:


A few things will happen as this shortwave trough propagates eastward: (1) the steering flow around the high pressure area will begin to breakdown, and this is the primary influence that is directing 99L westward, (2) a breakdown in the steering flow will cause a deceleration by 99L, (3) the progressive pattern of the shortwave trough over the northern United States will begin to transition from positively tilted to negatively tilted as it moves eastward, (4) a system that is more intense (which is likely if the steering pattern breaks down), will be more influenced by the northerly flow of a N-S oriented trough, which we can see occurring in the 5-day forecast of the 00z GFS run:


To summarize all of this, the short-term evolution of the two vorticity lobes in the Caribbean, and where consolidation occurs, is the first criteria to monitor for a future track into the GOM. After this, how progressive and the orientation of the shortwave trough over the northern CONUS will be significant on where a future landfall occurs. Below you can see there are still a wide range of possibilities in the GFS and ECMWF ensemble members. Anyone from Texas-Florida panhandle should continue to monitor the situation, as some of these details won't be known until 3-4 days from now.

ECMWF 00z ensemble members:


GFS 00z ensemble members:

[Kohlecane]

Great analysis USTropics Thank you! Agree that we will probably get more E and W shifts along the W/N GOM until that vortex gets figured out.

[cycloneye]

06z GFS= 939 mbs to Louisiana, New Orleans is in the crosshairs on the right side.

[N2FSU]

Moving due north or maybe slightly east of due north at landfall.


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