ATL: GERT - Post-Tropical - Discussion

[gatorcane]

The 12Z Euro is backing off even more on development (i.e. no development now at all through at least 4 days the run is out to so far). I think NHC development chances look too high.

[SFLcane]

The latest TWO is hedging away from anything short-term "early or middle of next week" - sometimes the TWO"s are too "optimistic" then have to backpedal when things don't quite go as planned...

Stewart...

[TheStormExpert]

It's really sad when you can't even trust your own model.

[RL3AO]

I have been giving the NAVGEM more weight in m forecasts than the "improved" GFS. The "improvements" have degraded the model to the point it is no longer usable, and not just for the tropics

It seems to create so many convective feedback issues. You can see the individual thunderstorm clusters that the convective scheme creates during the overnight hours. Then that small and perfectly round area of vorticity develops into a hurricane.

[weathaguyry]

So this is basically a garbage ghost storm, and this will probably end up like TD 4, if it even organizes that much?

[Kingarabian]

Probably a data issue. The models underestimate the SAL (especially the GFS) and it takes them a few runs to realize the atmosphere is too stable for development. The Euro has done it with these African waves twice this season. Just does a better job recovering.

I know I said it before, but the NASA model's dust depictions are important. Showed greater dry air content compared to the Euro and the GFS in the same time period.

[OuterBanker]

It’s amazing. Many are writing this off already. Expecting it to be developed already and since it hasn’t well that must be it for this system. Camille was a tropical wave for eight days before it developed. I don’t think we should be so hasty in writing 99L off quite just yet.

[Bocadude85]

It’s amazing. Many are writing this off already. Expecting it to be developed already and since it hasn’t well that must be it for this system. Camille was a tropical wave for eight days before it developed. I don’t think we should be so hasty in writing 99L off quite just yet.

It's August 4th..we should have had atleast 4 cat 5's by now...season cancel.

[cycloneye]

18z Best Track:

As of 18:00 UTC Aug 04, 2017:

Location: 9.9°N 28.4°W
Maximum Winds: 25 kt Gusts: N/A
Minimum Central Pressure: 1010 mb
Environmental Pressure: 1013 mb
Radius of Circulation: 180 NM
Radius of Maximum Wind: 70 NM

[jlauderdal]

This thread, like many others this season, is straying into a general discussion and comparison of the value of various global model guidance, versus discussing the model guidance for 99L.

Let's keep it on topic folks. If you want to continue a general discussion about models, you can always start a thread in TT.

Thanks.

edit: Actually, this is the general discussion thread - my bad. Still, let's keep it on topic.

Professor Tony confusing the students..

[RL3AO]

I know I said it before, but the NASA model's dust depictions are important. Showed greater dry air content compared to the Euro and the GFS in the same time period.

Remember, the NASA model isn't showing dry air. It's showing dust particles. That's not always the same thing.

[gatorcane]

Speaking of the NASA model, the 00Z run showed development, 81 hours below:

[MississippiWx]

Too broad and too much SAL for near-term development. 90L is likely to grab the F storm before 99L. It's August, yes, but that doesn't mean immediately favorable conditions. It's a gradual process to phase out the effects of SAL/shear. I think 99L has a much better chance at development as it approaches the Caribbean, similar to Bret and Don. However, conditions in the Caribbean/Western Atlantic shouldn't be as hostile to survival as it was for the former two storms.

[Kingarabian]

I know I said it before, but the NASA model's dust depictions are important. Showed greater dry air content compared to the Euro and the GFS in the same time period.

Remember, the NASA model isn't showing dry air. It's showing dust particles. That's not always the same thing.

Are dust particles less conducive for development compared to dry air?

[Kingarabian]

Speaking of the NASA model, the 00Z run showed development, 81 hours below:

Yeah it's not really good for predicting TC genesis in my opinion and I never use it for such.

[gatorcane]

12z UKMET delaying development significantly, but also further northeast:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 126 HOURS
FORECAST POSITION AT T+126 : 17.9N 56.6W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 10.08.2017 132 18.7N 57.7W 1011 35
1200UTC 10.08.2017 144 20.3N 60.6W 1009 38

Graphical output:

[gatorcane]

Garbage in Garbage out with these model runs, still a little dry East of -45W apparently.
I'm kind of bothered that the tracks are all further south since the Hispaniola destruction scenario is only a narrow possibility.
Anywhere else and a weak TS can become a strong Hurricane in 36 hours if there is a window of favorable conditions.

Looking closely at the last 12Z GFS run had it missed Hispaniola and Cuba just a little bit to the north, it would probably have developed it quite quickly with the track through the Bahamas and South Florida this time because the ridge is stronger this run than the 00Z run which had it swipe the East Coast of Florida plus the upper-level conditions looks similar on the 00Z as the 12Z.

[AutoPenalti]

It’s amazing. Many are writing this off already. Expecting it to be developed already and since it hasn’t well that must be it for this system. Camille was a tropical wave for eight days before it developed. I don’t think we should be so hasty in writing 99L off quite just yet.

It's August 4th..we should have had atleast 4 cat 5's by now...season cancel.

Post of the day.

[Alyono]

Sal outbreaks are most destructive in the caribbean due to a further acceleration of the low level winds. Conditions mat bemore hostile there

[BlowHard]

I am definitely not a professional meteorologist, nor do I pretend to be. I live in PR and do a little FB page of the local weather because I find tracking the hurricanes to be fascinating and also think there is a largely local twist that goes into that we cannot find elsewhere. So for two years, I've watched wind shear and sahara dust blow apart storms that were given high success rates to become tropical cyclones, as predicted by the NHC. Now I am looking at this one (which I do NOT want to develop, believe me) and I just don't see what other people are talking about in regards to SAL and shear. The shear is about as low as I've ever seen it and the SAL is light by local standards. (I could show you some pics that are basically all red, all over)....So I don't see the two things I usually look at first to determine if a storm will likely develop. Clearly, I am missing something. I know what part of that is, and I am wondering if someone can give me an explanation that will help me. I see people talking about ridges moving off the rockies, etc but I don't know what that results in or how it impacts the development of these storms. Is it that the ridge moves down and creates a high pressure area that alters the path of the storm? Can someone enlighten this rank amateur?