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Atlantic Tropical Action 2014


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I'd dismiss the GFS out of hand because its forecasts (MJO and otherwise) have been atrocious this season. I would only rely on the ECMWF in the short range for MJO forecasts and in the medium range for TC genesis probabilities. The GFS has been completely wrong in forecasting so many spurious TC genesis events this season, and its MJO forecasts have been equivalent to dog dung. I don't see any reason to change my forecast re: low expectations for a pick-up in activity over the next week (about which, I must add, I have been right thus far).

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I'd dismiss the GFS out of hand because its forecasts (MJO and otherwise) have been atrocious this season. I would only rely on the ECMWF in the short range for MJO forecasts and in the medium range for TC genesis probabilities. The GFS has been completely wrong in forecasting so many spurious TC genesis events this season, and its MJO forecasts have been equivalent to dog dung. I don't see any reason to change my forecast re: low expectations for a pick-up in activity over the next week (about which, I must add, I have been right thus far).

You obviously don't follow the tropics world wide, because then you would see the Euro is not good to lean on for tropical cyclone genesis.  Even in the Atlantic, it missed the formation of Dolly in the Bay of Campeche.  Of course, it appears the Euro has done a decent job at genesis in the Atlantic, mainly because the Atlantic has has been quiet thus not much TC genesis.  It often misses TC genesis, like several hurricanes in the Pacific.  

 

I will concede that the GFS doesn't handle the MJO very well.  But to solely rely on only one model for TC genesis, especially one that isn't too good on genesis to begin with, is crazy and really hurts your argument.     

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Sure 90L isn't the most beautiful easterly wave I've ever seen emerge from Africa, but at least it's maintaining some deep convection, which is a start.  The 12Z ECMWF ensemble is perhaps slightly more optimistic with it than the deterministic, although that's not saying much.  Let's see if it can survive the passage of that strong convectively-suppressed Kelvin wave first. 

 

post-378-0-87620700-1409864648_thumb.gif

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Getting back on topic..

 

There's an upper-level disturbance off the Florida coast that probably needs to be watched in my opinion. Once the front blows through the east coast this weekend and creates more of a temperature gradient (SE coast/Gulf Stream), this disturbance may become more convectively active. Fortunately, this has actually gained some support from the 12z ECMWF, CMC, and past runs of the UKMET. Even the NAM is starting to hint at a surface low developing off of SC. If something were to develop, proximity to land and time would probably be the huge limiting factors...

 

Still, its better than watching a moisture starved low traverse the record stability of the MDR

 

12z ECMWF 850 vort @ 72 hours (looks better on the hi-res maps in 3-hour increments) 

ScreenHunter_88Sep042030.png

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Charleston kind of backs up the last post a bit...

 

 

 

The greatest coverage should remain 
over the waters but by Sunday when the cold front drops south and 
the low becomes part of the baroclinic zone...plenty of lift should 
be present for numerous showers and thunderstorms. Because of the 
approaching cold front...NHC/wpc believe the low would probably not 
become tropical...though if the front slows down there could be some 
sort of sub-tropical hybrid off our coast late in the weekend
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Looks like the advertised area of disturbed weather has gotten it's act together in the SW Caribbean.  It appears to be slowly drifting NW.  It's in an area of lower shear currently, but it is ripping from west to east 30+ kts just north of the system from an ULL.  Models move that ULL westward and the shear abates to generally less than 20 kts.  But the newest trend in the models is to take the energy from the SW Caribbean and move it over to the East Pac and developing it over there.  Let's see if that's the case.  

 

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Looks like the advertised area of disturbed weather has gotten it's act together in the SW Caribbean.  It appears to be slowly drifting NW.  It's in an area of lower shear currently, but it is ripping from west to east 30+ kts just north of the system from an ULL.  Models move that ULL westward and the shear abates to generally less than 20 kts.  But the newest trend in the models is to take the energy from the SW Caribbean and move it over to the East Pac and developing it over there.  Let's see if that's the case.  

 

 

The main hindrance right now is lack of a low level circulation probably due to land interaction. There is some spin in the 700/500mb levels, but shear to the N of this area of disturbed weather has kept it in check. Condition may become a bit more favorable for potential development in a couple of days as it interacts with an Easterly Wave progressing W across the Central Caribbean and gets a bit closer to the Yucatan Peninsula. This area of disturbed weather is just N of the Monsoonal trough and should continue to fester for the next several days.

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No it's not sexy but quite a few ensemble members have well developed areas of low pressure in 3-4 days off the Carolina coast. Not sure if that would be classified as tropical, sub-tropical or just as an olf fashioned noreaster.

I think tropical development is very low in my opinion due to the fact it's close proximity to land and it'll get absorbed by the incoming frontal boundary.
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I think tropical development is very low in my opinion due to the fact it's close proximity to land and it'll get absorbed by the incoming frontal boundary.

 

Plenty of space out there for it to form just think Arthur,  water offshore there is plenty warm and if it organizes quick enough it could easily be a true tropical system....

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Plenty of space out there for it to form just think Arthur,  water offshore there is plenty warm and if it organizes quick enough it could easily be a true tropical system....

Almost half of the circulation of the broad low is inland already, it happens that convection is mostly in it's S and E quads. It's currently slowly moving WNW near the axis of a ridge to it's north. Little chance of development, IMO.

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Plenty of space out there for it to form just think Arthur,  water offshore there is plenty warm and if it organizes quick enough it could easily be a true tropical system....

Umm...the low level vorticity is half over land.  Most models, even the Euro, which WAS bullish with development, keeps it over land until it emerges it off the coast of North Carolina.  By then, it should be racing NE.  I just don't see tropical development. 

 

wg8vor.GIF

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The invest way out in the Eastern Atlantic continues to produce deep convection. I'm not exactly sure why the NHC lowered the chances of development today.

…because there's near-0% model support for even the most minor development (down from maybe 20% model support yesterday)?

 

There's absolutely zero reason for this piece of crap (which is less organized than even the most robust waves that, this season, have not even amounted to anything) to be anything other than near-0% development. A lot of the criticism of the NHC is unwarranted.

 

As Strat747 said, the fact that we are hoping for even a weak TS in peak season says a lot about this season's underperformance.

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…because there's near-0% model support for even the most minor development (down from maybe 20% model support yesterday)?

 

There's absolutely zero reason for this piece of crap to be anything other than near-0% development.

No offense but you have dismissed every single tropical threat this year. The GFS keeps the system alive until it reaches roughly 60W. You need to chill out.

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…because there's near-0% model support for even the most minor development (down from maybe 20% model support yesterday)?

 

There's absolutely zero reason for this piece of crap (which is less organized than even the most robust waves that, this season, have not even amounted to anything) to be anything other than near-0% development. A lot of the criticism of the NHC is unwarranted.

Who exactly is criticizing the NHC?  No one I see in this discussion thread is doing so.  

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…because there's near-0% model support for even the most minor development (down from maybe 20% model support yesterday)?

 

There's absolutely zero reason for this piece of crap (which is less organized than even the most robust waves that, this season, have not even amounted to anything) to be anything other than near-0% development. A lot of the criticism of the NHC is unwarranted.

 

As Strat747 said, the fact that we are hoping for even a weak TS in peak season says a lot about this season's underperformance.

This season isn't underperforming.  Sure it's quiet number wise, but everyone expected that, so if you ask me it's performing as expected.  3 out of 4 storms making hurricane status is not bad so far.  It's more hurricanes than last year had and the season isn't even at it's peak yet.  

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Asking why they lowered probabilities isn't being critical.

Well, if you've been a long-time observer of the tropics like me (since the late '90s) and have spent time on these forums, one of the most common weenie posts is a short statement asking why the NHC doesn't have higher probabilities for a system that usually never develops. If you have a good scientific reason to ask, then post it. In this case, you are talking about a model that, over the past several weeks, has consistently shown false tropical cyclogenesis events. The GFS has been terrible for even short-range cyclogenesis this season. The ECMWF, despite its cases of missing some weak TC genesis events, has been far better than the GFS, which has predicted even more TCs that never verified. As far as peak season is concerned, we're practically at the peak, so focusing on the number of days till the exact peak (September 12) is quite a reach considering the otherwise quiet season. If you look at the number of developments in the deep tropics, this season has been quite a dud, especially considering the recent string of quiet ATL seasons in the deep tropics with low ACE overall.

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Well, if you've been a long-time observer of the tropics like me (since the late '90s) and have spent time on these forums, one of the most common weenie posts is a short statement asking why the NHC doesn't have higher probabilities for a system that usually never develops. If you have a good scientific reason to ask, then post it. In this case, you are talking about a model that, over the past several weeks, has consistently shown false tropical cyclogenesis events. The GFS has been terrible for even short-range cyclogenesis this season. The ECMWF, despite its cases of missing some weak TC genesis events, has been far better than the GFS, which has predicted even more TCs that never verified. As far as peak season is concerned, we're practically at the peak, so focusing on the number of days till the exact peak (September 12) is quite a reach considering the otherwise quiet season. If you look at the number of developments in the deep tropics, this season has been quite a dud, especially considering the recent string of quiet ATL seasons in the deep tropics with low ACE overall.

 

You don't need a model when you have a perfectly good satellite loop to work with. And I'm guessing that you haven't looked at the ECMWF ensemble mean which keeps the system around almost as long as the GFS. The GFS and ECMWF both maintain a somewhat organized system for at least the next 48-72 hours and are banking on the circulation remaining weak enough that the dry air and the approaching Kelvin wave eventually finish it off. The global models are great for establishing where tropical cyclone genesis might occur and nothing more until the system actually does or doesn't develop.

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Keep an eye on the SW Caribbean over the weekend. Convection continues to fester this afternoon and the Euro Ensemble mean is suggesting below normal pressures across the Western Caribbean/Western Gulf into next Thursday across that part of the Atlantic Basin.

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