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Atlantic Tropical Action 2012 - Part II


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The 12Z GFS ensemble mean has two SLP minima associated with the "Senegal Screamer"TM threatening the US on 8/22: one over S FL prior to heading NW into the GOM and one over E NC. This is still way out in Lala land, but it is interesting nonetheless since it is a system the GFS wants to quickly develop just off Africa in only about three days. Regardless, it will have to fight El Nino climo as well as high latitude climoto make it that far.

1) El Nino climo for CV storms: I was able to find no more than six storms that formed east of 45 W that either hit the U.S. or went into the W. Caribbean:

-Frances and Ivan of 2004: weak Nino

-Dog of 1951: weak Nino (using the older ENSO classification)

-#1 of 1900: weak to borderline moderate Nino

-#3 of 1899: strong Nino

Per the new ENSO classification: Carol of 1953..weak Nino

So, it appears that it helps if the Nino is weak (as is the case today) as 5 of the 6 storms were during weak to borderline moderate Nino's. Also, three of these six had E ATL WSW motion.

2) Hurting its chances significantly is that it forms near 17N. Regarding the referenced six storms, five formed way down between 10N and 12N while only Carol of 1953 was up at 16N.

Since 1851, only six storms formed N of 15N/E of 45W and made it to the U.S.:

-#6 of 1893: 18.1N

-Carol of 1953: 16.0N

-Connie of 1955: 15.3N

-Diane of 1955: 17.0N

-Ione of 1955: 15.4N

-Ike of 2008: 17.2N

In summary: whereas any potential WSW motion would help its chances to make it at least pretty far west, the expectation for it to be as far north as ~17N definitely hurts the chances of it making it to the US. Also, El Nino climo hurts the chances of a US hit although it being only a weak Nino gives it a better chance than if it had been strong.

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Whats interesting is according to the loops this is not nearly as high in latitude as the models are currently suggesting, the rotation and convection is all below 15N (I'd say around 13.5N) which obviously may make a rather big difference and as superstorm's image shows, that may actually make a large difference with regards to its developmental chances early on.

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Whats interesting is according to the loops this is not nearly as high in latitude as the models are currently suggesting, the rotation and convection is all below 15N (I'd say around 13.5N) which obviously may make a rather big difference and as superstorm's image shows, that may actually make a large difference with regards to its developmental chances early on.

Once it passes Dakar and the sounding from there is incorporated we could see a model shift to the south.

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Can we have a separate banter thread for all of the 384 hr GFS and nonsense model postings?

It's not even a tropical cyclone yet, please relax. Nobody takes the ensembles seriously; and mainly posted so people don't overlook the potential of this threat. GaWx's post is very good and tells us that it's not likely something makes it across but also that it's not completely impossible.

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It's not even a tropical cyclone yet, please relax. Nobody takes the ensembles seriously; and mainly posted so people don't overlook the potential of this threat. GaWx's post is very good and tells us that it's not likely something makes it across but also that it's not completely impossible.

384 hours = 16 days. No one is going to overlook a giant hurricane in the Atlantic... it's not as if they suddenly appear.

Also you contradict yourself. If no one takes the ensembles seriously, why are you posting them so people "don't overlook the 'threat'"?

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384 hours = 16 days. No one is going to overlook a giant hurricane in the Atlantic... it's not as if they suddenly appear.

Also you contradict yourself. If no one takes the ensembles seriously, why are you posting them so people "don't overlook the 'threat'"?

I don't recall such a strong signal from the GFS ensembles for a decent African wave train this year, thought it was worth posting but I admit that I'm not aware of their accuracy; according to PSU they are not worth posting. My thinking was how could the low resolution ensembles depict a hurricane like that?

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I don't recall such a strong signal from the GFS ensembles for a decent African wave train this year, thought it was worth posting but I admit that I'm not aware of their accuracy; according to PSU they are not worth posting. My thinking was how could the low resolution ensembles depict a hurricane like that?

http://raleighwx.americanwx.com/models/gfsensemble/members/12ztropf384.html

There is every single ensemble member for 384 hours of the 12Z GFS

Notice how divergent the solutions are? It's late August at that time, so of course some of the members are going to show a TC... but put aside your weenie fantasies for a moment and also notice how many do not show anything of the sort.

(Note: Apologies to others for posting any 384 hr model output... attempting to be educational for a moment.)

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And are we really obsessing over the latitude of an MCS over Central Africa? You guys really need to relax, it's a long season.

I don't think thats such a bad thing really, if it comes off 3-4 degrees south of where the majority of the models are trying to form it, that will have a big difference to its *developmental* chances, due to SST's etc.

I'm not talking about this system and its latitude right now with regards to track, I'm talking from the point of a possible TC coming from this. The track at this stage will shift many times yet IF it develops at all.

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I don't think thats such a bad thing really, if it comes off 3-4 degrees south of where the majority of the models are trying to form it, that will have a big difference to its *developmental* chances, due to SST's etc.

I'm not talking about this system and its latitude right now with regards to track, I'm talking from the point of a possible TC coming from this. The track at this stage will shift many times yet IF it develops at all.

It's two days away from even reaching the Atlantic. It's a pointless conversation.

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It's two days away from even reaching the Atlantic. It's a pointless conversation.

How is it pointless to discuss something that may only be 2-3 days from development, plenty of models try to develop at least a weak system from this wave in the near future (IE within 96hrs)

I'm guessing even something within 96hrs is not worth pointing out ever again then...ho hum!

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How is it pointless to discuss something that may only be 2-3 days from development, plenty of models try to develop at least a weak system from this wave in the near future (IE within 96hrs)

I'm guessing even something within 96hrs is not worth pointing out ever again then...ho hum!

Talking about immediate development off the coast of Africa is ok - we can probably forecast that with some skill. Then extrapolating into its chances of becoming a hurricane or reaching the United States is pointless drivel. There was a whole lot more of the latter than the former.

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The last couple of years the GFS has been very good when it consistently predicts a strong tropical system, so this is definitely something to watch with interest. That is about all that I take away now. Does anyone remember the system 5-10 years ago that all of the models forecast to develop quickly and to be a monster but then poofed soon after it hit the water? It did reach depression or even storm status but then died out despite very favorable conditions and unanimous model support. The NHC obituary discussion said something like, "How little we understand about cyclogenesis in the deep tropics...." That captured what I find so interesting about the tropics.

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