Ex Invest 93L in Central Atlantic

[bvigal]

So what happened? The GFS especially was quite bullish on what is now 93L and it looked for a few runs there like we might not hear from Luis again until Xmas with the likes of the hurricane it had near P.R. Now, it looks doubtful that either of these two will develop- at least not yet. So that begs the question- why? We can throw out "because it is the model NCEP" as I remember other models showing robust development out of this system too. So a suite of models was on and now they are somewhat off, but not totally. What happened? What new information are the models "seeing" that has "changed their minds"? I know that tropical cyclogenesis is hard to predict but this is interesting and I, among others I am sure, would like to understand better why the model guidance acts like this sometimes. Who knows- perhaps we will see something like Felix last season where by there is a strong hurricane in the real world but a hump on the isobars on the GFS. Thoughts?

I don't know... the stuff we were looking at on GFS a couple days ago aren't these invests, at least not 92. Here, I'll post pic again:

This is GFS for 8amEDT 19th of August. The storm in the Carib, just past Puerto Rico over Hispaniola could possibly be 93L. 92L, today already near 50W, will be in that area by 15th/16th. The second storm in the model, nearing the Windwards in the picture, could be 93L. Or, knowing how models are that far out, the left-most storm could have referred to what is now 93L, and the next one we don't see off Africa yet!

[Derek Ortt]

"Splain me this please. What do you see that makes you give it a low percentage chance of developing when the NHC is saying it could become a TD within a few days? I am talking synoptics, etc. here as opposed to what the NHC generally has to say due to the parameters put on them.

I posted this while the others above it were asking the question quicker. Can you go into more detail?

what I am seeing is a lack of inflow into the center. The convergence is going into the band away from the center (not uncommon for systems embedded within the ITCZ) This should keep the vorticity from rising near the center, not allowing for the formation of a closed surface circulation. I am also not seeing the greatest of model support for development

[Ed Mahmoud]

Derek's home made semi-close-up visible loop.

No idea if it is surface or not, but it sure looks like a closed circulation at some level.


Looks like it has convection ahead of it, and some convection wrapping in from the East.

I think difference between Derek and NHC outlooks, NHC's job is public protection, so they have to mention development as long as there is any reasonable chance, and Derek is more of a pure academic/science guy.

[bvigal]

Well it's certainly true the GFS has done an about-face from 3 days ago, now keeping everything sort of contained in the ITZ!

[Category 5]

Derek is more of a pure academic/science guy.

Couldn't resist.

[cycloneye]

I am also not seeing the greatest of model support for development

Derek,HWRF and GFDL makes 93L a cat 2 hurricane.

[curtadams]

So what happened? The GFS especially was quite bullish on what is now 93L and it looked for a few runs there like we might not hear from Luis again until Xmas with the likes of the hurricane it had near P.R. Now, it looks doubtful that either of these two will develop- at least not yet.

Broken record alert - all the models are poor with cyclogenesis. We don't understand the process *and* the grids are probably too coarse *and* our upper-air oceanic data is poor. All they can do is mark certain areas as favorable. They are particularly bad in complicated areas like the ITCZ.

[BigA]

Tonight may be crucial in terms of any future development. If it can get a bit of deep "red" convection to the northeast of the southern band, near the assumed center, it would likely have a good shot.

[KWT]

I can see what Derek says about the convection focusing on the convection infront thats very obvious on the various loops I've seen. The key is will convection also fire over the center as well like it had down earlier. I've seen those blobs in front of developing systems really put the brakes on development at least for a little while.

[Derek Ortt]

Derek's home made semi-close-up visible loop.

No idea if it is surface or not, but it sure looks like a closed circulation at some level.


Looks like it has convection ahead of it, and some convection wrapping in from the East.

I think difference between Derek and NHC outlooks, NHC's job is public protection, so they have to mention development as long as there is any reasonable chance, and Derek is more of a pure academic/science guy.

I do try and stick strictly with the data.

I know I blew the update this morning (need to stop doing the 8 a.m. outlook immediately upon waking up, lol. Have to get up at 7)

[Ed Mahmoud]

Derek's home made semi-close-up visible loop.

No idea if it is surface or not, but it sure looks like a closed circulation at some level.


Looks like it has convection ahead of it, and some convection wrapping in from the East.

I think difference between Derek and NHC outlooks, NHC's job is public protection, so they have to mention development as long as there is any reasonable chance, and Derek is more of a pure academic/science guy.

I do try and stick strictly with the data.

I know I blew the update this morning (need to stop doing the 8 a.m. outlook immediately upon waking up, lol. Have to get up at 7)

On model thread, you said Canadian develops wave after 93L, but looking at vorticity, looks like Canadian merged vorticity following 93L with 93L. I'm not sure Canadian is wrong, because (hard to tell with infrequent update Euro satellite images) I think I see a curvature trying to catch 93L.

[jhamps10]

Tonight may be crucial in terms of any future development. If it can get a bit of deep "red" convection to the northeast of the southern band, near the assumed center, it would likely have a good shot.

last night it was able to do just that very thing. I expect it to do so tonight as well.

[Weatherfreak14]

Well, tonight is very impotant for this storm, then it has to maintiain that convection over the center...... This is moving into better conditions for doing just that. I think it will have a better chance after it passes 40w.

As for the models doing a complete 180 on this system, i think it will continue to show a lack in the cyclongenis until they really start to develop then i think the models will start to latch on.

[KWT]

The only issue is there is a lot of mess from various ITCZ features that may compete for inflow and that tends to take time to work out, esp when the system may well stillbe attached to the ITCZ anyway.

[cycloneye]

The 18:00 UTC Best track for 93L:

AL, 93, 2008081118, , BEST, 0, 110N, 292W, 25, 1008, DB, 34, NEQ, 0, 0, 0, 0, 1011, 180, 35,

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/

[jhamps10]

The 18:00 UTC Best track for 93L:

AL, 93, 2008081118, , BEST, 0, 110N, 292W, 25, 1008, DB, 34, NEQ, 0, 0, 0, 0, 1011, 180, 35,

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/

well isn't that nice. we've got an eye..... in all seriousness though looking at the satellite image above my posting, it would sure make a lot of novice folks seriously think that was an eye instead of a break in convection. 93l looks good for development right now, it may take a bit of time, but it looks pretty good to me.

and I'm also not buying that quick turn by GFDL seems way out of wak to me.

[KWT]

Best track also has this about the same strength as 92L as well. 93L is pretty active in terms of convection, just needs to centralise that convection a little more though IMO otherwise its going to take a while for this to get going.

[Weatherfreak14]

I wonder why the NHC hasent put a floater on this yet, its whthin range now.... Anywayz it looks like convection trying to pop near the center?????

[Derek Ortt]

a floater is available here

http://www.nwhhc.com/satellite.html

it is labeled as invest_08 (I considered the one before and this one as disturbances within the same broad low; thus, the same invest)

[Steve]

>>Not sure what's going on with this season.. I mean if things can't get going now when will they? The GFS shows absolutely nothing for the rest of the month. This season is rapidly getting disappointing.

Not sure why you would even post this. This is nuts. 1) It's not the peak of hurricane season, and often August is completely without tropical activity until the end of the month. The fact that you are looking at 2 real invests rather than a giant bunch of dry air and subsidence over the entire basin should say something. 2) What do you care what the GFS shows or doesn't show? The GFS isn't God. It's not even all that great to begin with on long term, pattern stuff. They've been working on it for years and only in the last season or so has it really gotten better with not constantly putting a trough in the central or western Atlantic after a 5-7 day period (aka known bias). 3) As for the season getting "rapidly disappointing," people post that stuff every year. There are threads every year known as "Season Cancel" threads. You have to be patient and not jacked up on a caffeine overload on top of an ADHD fit. Seriously. Both major seasonal predictors (NOAA and Colorado State) just upped their seasonal totals into the mid to upper teens in number of storms. That's insane in any year, and if it verifies, will most likely put 2008 in the Top Few ALL TIME seasons. Just be patient and don't get all in a tantrum. Nature is going to take its own sweet time to do what it wants to do. You've been around here long enough to know that.

Steve