ATL: IDA - Models

[aspen]

The HWRF really has trouble keeping focus on these invests. The 06z run gets stuck over South America, but if you look on the simulated IR view, the system consolidates are moved into the NW Caribbean while the HWRF’s focus remains stuck.

[BobHarlem]

0z UKMET


6z HMON looks like it does not develop 99L at all.

Models are still very much in flux right now, I wouldn't use any of them as a guide.

[Blown Away]

EURO 00z...

[Kohlecane]

Quite the E movement over the past 3 runs from the GFS

[tailgater]

The 06 Gfs run today would be close to worst case senecio for my area thankfully we are 5 days out. But a strong storm moving slowly to my west not a good thing for anyone I guess.
Hopefully conditions won’t be as favorable as they are thinking at the moment.

[skyline385]

EURO 00z...

EURO has it as a weak Cat1 at landfall though. The storm is moving fast in the models so it is a possibility...

[skyline385]

Anyone else notice how the 6Z GFS has the system stalling inland before dissipating? The precipitation plots look bad...

[tailgater]

Vorticity showing up night vis loop near 13N 75.3 W on the SW edge of the heaviest convection.

[kevin]

Anyone else notice how the 6Z GFS has the system stalling inland before dissipating? The precipitation plots look bad...

Yeah, I know the value of an individual run is very low at the moment since it's still so far out, but it does show the potential for a very bad rain event. The run has a max. of 572 mm (23 inches) of rain with large 300+ mm (12+ inches) regions such as New Orleans.

[Kohlecane]

This makes me wonder a bit, as mentioned earlier about the Vort and wave axis and determining where a COC truly forms, this sort of depicts that either way S or N it will find it's way into the W/C GOM. Healthy environment ahead and ridging seems to decouple on most consensus models as of now, so speed I would think will play the biggest factor IMO. Look at Grace when she was she entered the the CAB moving at 20+MPH, good environment(although sst's were nothing compared to the GOM ATM) but its forward speed decoupled/relocated that LLC/MLC a few times tracking that at 7 days out had it from SE Coast to SFL and eventually a low rider to the GA's and into MX.

[IcyTundra]

06Z GEFS the operational GFS is still on the far eastern edge of the ensemble spread.

[BobHarlem]

6z HWRF and HMON do not develop 99L (or at least latch on to the wrong thing)

[IcyTundra]

6z HWRF and HMON do not develop 99L (or at least latch on to the wrong thing)

HWRF and HMON aren't going to be very helpful until we get a closed circulation.

[NDG]

The trend by the GFS is for ridging to be not as strong across the SE US as earlier forecasted thus a higher risk for a more northerly track across the GOM by 99L.

[IcyTundra]

[kevin]

https://www.weathernerds.org/tc_guidance/images/AL99_2021082500_ECENS_large.png?1629893291

Wow, looks like the euro is pretty much 100% into Texas or Louisiana (post-Yucatan).

[Kohlecane]

https://www.weathernerds.org/tc_guidance/images/AL99_2021082506_GEFS_large.png?1629891507

06Z GEFS the operational GFS is still on the far eastern edge of the ensemble spread.

I've never quite understood what determines this, does the operational have a algo that it decides more favorable based on set up. Never really understood why the OP is not a consensus or the most mean ensemble.

[ronjon]

https://www.weathernerds.org/tc_guidance/images/AL99_2021082500_ECENS_large.png?1629893291

Wow, looks like the euro is pretty much 100% into Texas or Louisiana (post-Yucatan).

Unfortunately the odds of a major hurricane landfalling in the US are now getting more likely.

[kevin]

https://www.weathernerds.org/tc_guidance/images/AL99_2021082506_GEFS_large.png?1629891507

06Z GEFS the operational GFS is still on the far eastern edge of the ensemble spread.

I've never quite understood what determines this, does the operational have a algo that it decides more favorable based on set up. Never really understood why the OP is not a consensus or the most mean ensemble.

As far as I understand the OP uses the most accurate data or at least that is deemed 'closest to reality'. Furthermore, depending on the model, the OP uses a significantly better resolution than the other members. The other members have some perturbations with respect to these 'most accurate values' due to the uncertainties. In typical chaos theory fashion these tiny changes result in significant changes of the weather forecast. However, a Gaussian uncertainty bound in the input doesn't necessarily lead to a nicely centered uncertainty envelope (if they even use a Gaussian uncertainty bound, they probably use something way more complicated). In other words, using a -5 to +5 range for the input doesn't have to lead to a -5 and +5 range in the output, it could be -1 to + 14. I guess what's going on here is that apparently any perturbations with respect to the input data mostly seem to prefer more western tracks. This is only based on my understanding and also extremely simplified, but I hope this gives an idea of what's going on.

Sidenote: some models also have a control or para run such as HWRF, which has HWRF-P. Actually I think most models have them (including GFS and the euro), they're just not readily available for some of them. These runs use the exact same input as the OP, but with a lower resolution. If the OP & para differ significantly this is an indicator that the difference in resolution leads to a very different outcome and as such the other low-res ensemble members are not worth that much. However, if the OP & para are very similar (which is usually the case), it shows that even a slightly worse res can still run the simulation quite well and this thus gives more confidence towards the other ensemble members.

[PTrackerLA]

The crazy thing is we are only about 5 days out from landfall but maybe 2 even 3 days away from this being at least a TD/TS. Makes me wonder if PTC advisories may start sooner than we normally expect.