ATL: INVEST 92L - Discussion

[nautical wheeler]

Recon data would sure be nice.

If there is indeed a LLC forming under that MLC one would expect that convection should start to fire and tighten this thing up in the next 12 hours.

[Alyono]

Watch the rgb satellite loop. Wxman57, Alyono and I have all stated in recent posts that we can see a new LLC developing around 22.0N, 90.5W. We already gave our reasons why and I backed up mine with annotated satellite images. It just so happens that the new LLC is forming under that MLC but we are not confusing the two by any means - we certainly know the difference. The rgb satellite will show you both MLC and LLC to a large degree as long as the MLC doesn't obscure the LLC below. You may very well be seeing something different, but we all have many years a lot of experience in watching these and that's what we see.

Hold on... I dont put it that far east. The LLC is still west of there.

What I said, watch the broad low. Pay no attention to any eddy that forms, whether the eddy forms to the east or the west

[ozonepete]

Watch the rgb satellite loop. Wxman57, Alyono and I have all stated in recent posts that we can see a new LLC developing around 22.0N, 90.5W. We already gave our reasons why and I backed up mine with annotated satellite images. It just so happens that the new LLC is forming under that MLC but we are not confusing the two by any means - we certainly know the difference. The rgb satellite will show you both MLC and LLC to a large degree as long as the MLC doesn't obscure the LLC below. You may very well be seeing something different, but we all have many years a lot of experience in watching these and that's what we see.

Hold on... I dont put it that far east. The LLC is still west of there.

What I said, watch the broad low. Pay no attention to any eddy that forms, whether the eddy forms to the east or the west

I understand, but I thought you agreed that any LLC that does form will be well north of the best track position. Do you think it's south of 22.0N? i.e. where do you think the most likely area for an LLC to develop is? I thought you agreed that the LLC that best track has been following is basically dissipated and that any new one would form farther north... I always talk about the most likely place for an LLC to form and the best physical evidence that it's happening. We al know you don't follow a single eddy and ignore the others. But in the end, one will get under the MLC and they'll consolidate if conditions allow. Right?

[stormhunter7]

so the "center"... of the surface low at 20.8n 91.8w.. moving to the sw, is going to fade away? And a newer center is forming well to the NE up under the ULL?

http://www.ssd.noaa.gov/PS/TROP/floater ... -long.html

[Alyono]

the broad low is still centered near 21.5N and 91.5W. It hasn't moved all day

[ozonepete]

so the "center"... of the surface low at 20.8n 91.8w.. moving to the sw, is going to fade away? And a newer center is forming well to the NE up under the ULL?

http://www.ssd.noaa.gov/PS/TROP/floater ... -long.html

That sfc low you referred to is pretty much gone already. In a tropical disturbance that has an MLC (which is all this is right now) many LLCs develop and rotate around each other and form and dissipate until one merges with the MLC dominates. In this case a new LLC will have to form to the north under the MLC or near it. Where the old LLC was there is no mid-level vorticity and it seems very unlikely the current MLC would dissipate and reform over that area. The physics for that latter case don't make sense.

[Dean4Storms]

the broad low is still centered near 21.5N and 91.5W. It hasn't moved all day

Actually it's dropped southward, now near 20.9N 91.5W and still moving southward.

[NDG]

the broad low is still centered near 21.5N and 91.5W. It hasn't moved all day

Actually it's dropped southward, now near 20.9N 91.5W and still moving southward.

Yeah, it has continued moving southward as I type this.

[ozonepete]

the broad low is still centered near 21.5N and 91.5W. It hasn't moved all day

Actually it's dropped southward, now near 20.9N 91.5W and still moving southward.

Yes it has. And that purely surface circulation will continue dropping south and then dissipate. It hasn't been involved in the regeneration that's going on to the north at all. Any new LLC that develops will be centered NE of there.

[Bailey1777]

i have to say ive been on here for years and this is the most confused ive ever been....lots of differing opinions-pro- and not in line much with the nhc.

[wxsouth]

I agree that the low level center will continue to drop south and weaken. However, as of 00z (sunset), the only sfc center supported by satellite and surface obs was this center. There was no evidence of any westerly surface flow to the north of the low level center. Its certainly possible that a sfc center could form farther north, but unless there's a ship in the area overnight, there won't be any way to know until after sunrise. In addition, without significant convection firing overnight underneath the mid/upper low, I doubt the circulation will build down to the surface.

I suspect the global models are correct in keeping this system broad and sloppy for the next several days. Synoptically, it just doesn't look good for TC formation.

[stormhunter7]

http://www.cnn.com/video/data/2.0/video ... f.cnn.html


But it could explode as it drifts ssw?

[nautical wheeler]

Meh, I dunno. This thing just looks kind of sick. We're looking at a MLC that is lacking any deep convection and I don't see how it's going to form a prominent LLC with that being the case. Looks like it's dealing with some dry air ATM as well. Maybe this thing just kind of tumbles itself northward as a plume of moisture.


This is my very amateur take.

['CaneFreak]

I now put the chances of anything developing from this mess at 30 % and that may be generous. Let's see what tomorrow brings but I don't have my hopes up. Have a good night all.

[ozonepete]

I agree that the low level center will continue to drop south and weaken. However, as of 00z (sunset), the only sfc center supported by satellite and surface obs was this center. There was no evidence of any westerly surface flow to the north of the low level center. Its certainly possible that a sfc center could form farther north, but unless there's a ship in the area overnight, there won't be any way to know until after sunrise. In addition, without significant convection firing overnight underneath the mid/upper low, I doubt the circulation will build down to the surface.

I suspect the global models are correct in keeping this system broad and sloppy for the next several days. Synoptically, it just doesn't look good for TC formation.

A good analysis. Broad and sloppy has been its calling card. And yes there's a dearth of data down there to tell us what's going on at the surface overnight unless we get lucky with a microwave or ASCAT sat passing over it. One thing of note is that it seems that the first upper trough that dipped down into the Gulf is passing east now and will probably leave it behind. This may allow it to wallow down there for a while longer and give it time to consolidate.

[EastCoastlow]

Another thing to keep an eye on if a vertically stacked cyclone can develop would be the potential for enhancement from the upper level trough to the north. It’s in a favorable orientation for baroclinic enhancement of any surface low. This is another reason we see the models developing large MCS’s and weak surface lows to the north/northeast of the primary surface circulation. There is favorable jet dynamics for increased upper level divergence over the Western Gulf. Thinking of it very simply removal of mass in the upper levels must be replaced, thus inducing surface pressure falls and convergence. If you removed a cup full of water from a bathtub it will almost immediately be replaced by surrounding water.

[Dean4Storms]

I can see an LLC near 22.5N 90.5W in this loop drifting North, if you can't see then you just don't want to see it. It's faded just like the LLC out to the SW!
Speed it up if you need to and zoom!

http://www.ssd.noaa.gov/PS/TROP/floater ... -long.html

[Annie Oakley]

JonathanBelles: what say you?

[JonathanBelles]

JonathanBelles: what say you?

I say that I just got home from a Rays game, and i'm lucky I saw this. lol

On first inspection I would say it looks better than it did earlier today. If it gets convection going later tonight during Dmax, we may be looking at a different story tomorrow. It may get better aligned overnight, and should have time to develop a bit.

[ozonepete]

JonathanBelles: what say you?

I say that I just got home from a Rays game, and i'm lucky I saw this. lol

On first inspection I would say it looks better than it did earlier today. If it gets convection going later tonight during Dmax, we may be looking at a different story tomorrow. It may get better aligned overnight, and should have time to develop a bit.

Yeah, let's see what DMAX does. I think it inhaled a lot of drier air from over the Yucatan in the last few hours. It didn't occur to me earlier how strong the influence could be, but when the diurnal sea breeze thunderstorm blowup over the Yucatan dies out at sunset it also causes a lot of descending drying air from the dying thunderstorms to get pushed down to the surface. This drier air probably got ingested into the circulation of our disturbance and further decreased its ability to produce thunderstorms offshore around its center. All of that should change overnight.