ATL GUSTAV: Tropical Depression - Discussion

[HURAKAN]

Looks like it's in its way to TD 7. Convection developing during DMIN and the rotation is impossible to miss.

[jlauderdal]

To me it looks like its already gaining appreciable lattitude and that turn to the NW-WNW may be commencing soon enough.

what direction do you have it going now?

I see WNW right now. I'm using this loop:

http://www.ssd.noaa.gov/goes/flt/t2/loop-vis.html

ok so you think it will head more NW in the future

[Ivanhater]

[ericinmia]

I know this is IR, and I am really not trying to track a Mid or Low level circulation... because at this point there isn't much to track and I don't want to get dizzy/headache. But it appears the majority of the convection has moved NW today... Many times with a weak system like this, especially since it is still a wave axis, there is a higher probability that the center will reform/move with the large amounts of sustained convection.

It's sort of a nuclear 'Home improvement" sunday, so i'm not really in the mood for any sort of dedicated analysis... so my ideas could be way off base here but those last few frames of IR really do appear that the main convection has moved NW today. Maybe PR is in for some rain/storms?
-Eric

http://www.meteo.psu.edu/~gadomski/SAT_ ... im8ir.html

[ConvergenceZone]

This should be a player in the gulf of mexico eventually, in my opinion....I don't think the shear will be near as bad as folks think, probably enough though to prevent rapid intensification....

[tpr1967]

Hey guys check out the bouy report just n of possible center.2 mb pressure drops in 24 hrs and increasing winds in thunderstorms.

http://www.ndbc.noaa.gov/station_page.php?station=42059

[KWT]

Yeah I agree wxman57 I've been seeing about a 285 motion over a longer term though the last 2hrs does seem to be a good bit further north, may well be close to 290-295 now. Still very tough to call whether this hits hispaniola, looks like its going to come very close indeed!

Also does indeed look like its developing into a tropical system, though the NHC may wait till recon unless it become perfectly obvious this is a TD...

[Tropicswatcher]

Look at that solid line of thunderstorms heading northward :

[Clipper96]

The center is southwest of the sundown blow-up; which should circle southwest as it orbits around and eventually becomes co-located with the LLC. - This may fake people out into thinking movement is left of WNW.

[Sanibel]

Don't dismiss a crazy center jump into that round convection burst up near 15.5N

If that happens we are talking huge jump N of NW.

[Clipper96]

The center is southwest of the sundown blow-up; which should circle southwest as it orbits around and eventually becomes co-located with the LLC. - This may fake people out into thinking movement is left of WNW.

...just as some are now being faked out into thinking it's right of WNW.

[wxman57]

Was just taking a good look at the lower level winds across the southern and central Caribbean and I think that most of the models may be steering us the wrong way as far as where this system may go. First of all, it's definitely zipping along at about 16-18 kts over the past 6-12 hours. I looked at the latest analysis of 850mb winds across the Caribbean and I see 15-25 kt winds out of the east all the way to Honduras. At the rate 94L is moving, it'll be passing Haiti tomorrow afternoon (longitude-wise) at a time when both GFS and Canadian (that turn the system north) still show easterly winds at 15-20 kts from about 18N south to South America.

Now, to move to where the European has it at 168 hrs (over central Cuba) it would have to average only 4.6 kts forward speed from now until then. And the Euro doesn't have it near Haiti for 4 DAYS! At the speed it's moving now, that would be closer to 24 hrs, not 4 days.

Global models definitely see a weakness in the ridge developing by late Monday or Tuesday near the DR and eastern Cuba. But by that time, 94L may be well west of that weakness and heading toward Honduras/Nicaragua.

So my thinking is that it bypasses any developing weakness over eastern Cuba/DR because it's moving too fast now and won't be at that longitude when the weakness develops. With a ridge over the NE Gulf and southeast U.S., steering currents should take it into Central America, perhaps the southern Yucatan in about 60-72 hours. That's allowing for some slowing.

Oh, and the last good position I got (2215Z) was about 13.8N/68.5W. Not a lot of surface obs nearby, but what few there are don't indicate any LLC yet.

[KWT]

That far west wxman57?
I'd have placed it around 67.5W closer to that SW blow up of convection but who knows. What I do agree with you is the models are getting this one wrong at the moment, its moving a good deal faster then the models prog, I clocked about 19mph over 12hrs a few hours ago based on a rough estimate so even if thats off its still pretty much hurtling along, probably 290 would be my guess at the current motion.

wman57, what about the weakness left by Fay could that not indcue a more northerly track in the western Caribbean...got to agree though this looks Yucatan bound I rekcon, then who knows from there...

[ROCK]

Was just taking a good look at the lower level winds across the southern and central Caribbean and I think that most of the models may be steering us the wrong way as far as where this system may go. First of all, it's definitely zipping along at about 16-18 kts over the past 6-12 hours. I looked at the latest analysis of 850mb winds across the Caribbean and I see 15-25 kt winds out of the east all the way to Honduras. At the rate 94L is moving, it'll be passing Haiti tomorrow afternoon (longitude-wise) at a time when both GFS and Canadian (that turn the system north) still show easterly winds at 15-20 kts from about 18N south to South America.

Now, to move to where the European has it at 168 hrs (over central Cuba) it would have to average only 4.6 kts forward speed from now until then. And the Euro doesn't have it near Haiti for 4 DAYS! At the speed it's moving now, that would be closer to 24 hrs, not 4 days.

Global models definitely see a weakness in the ridge developing by late Monday or Tuesday near the DR and eastern Cuba. But by that time, 94L may be well west of that weakness and heading toward Honduras/Nicaragua.

So my thinking is that it bypasses any developing weakness over eastern Cuba/DR because it's moving too fast now and won't be at that longitude when the weakness develops. With a ridge over the NE Gulf and southeast U.S., steering currents should take it into Central America, perhaps the southern Yucatan in about 60-72 hours. That's allowing for some slowing.

Oh, and the last good position I got (2215Z) was about 13.8N/68.5W. Not a lot of surface obs nearby, but what few there are don't indicate any LLC yet.

thanks for your input...that puts to rest a lot in here for the time being...


Deltadog- right on!

[Derek Ortt]

Was just taking a good look at the lower level winds across the southern and central Caribbean and I think that most of the models may be steering us the wrong way as far as where this system may go. First of all, it's definitely zipping along at about 16-18 kts over the past 6-12 hours. I looked at the latest analysis of 850mb winds across the Caribbean and I see 15-25 kt winds out of the east all the way to Honduras. At the rate 94L is moving, it'll be passing Haiti tomorrow afternoon (longitude-wise) at a time when both GFS and Canadian (that turn the system north) still show easterly winds at 15-20 kts from about 18N south to South America.

Now, to move to where the European has it at 168 hrs (over central Cuba) it would have to average only 4.6 kts forward speed from now until then. And the Euro doesn't have it near Haiti for 4 DAYS! At the speed it's moving now, that would be closer to 24 hrs, not 4 days.

Global models definitely see a weakness in the ridge developing by late Monday or Tuesday near the DR and eastern Cuba. But by that time, 94L may be well west of that weakness and heading toward Honduras/Nicaragua.

So my thinking is that it bypasses any developing weakness over eastern Cuba/DR because it's moving too fast now and won't be at that longitude when the weakness develops. With a ridge over the NE Gulf and southeast U.S., steering currents should take it into Central America, perhaps the southern Yucatan in about 60-72 hours. That's allowing for some slowing.

Oh, and the last good position I got (2215Z) was about 13.8N/68.5W. Not a lot of surface obs nearby, but what few there are don't indicate any LLC yet.

however, that's assuming that the center does not relocate farther north. If it does, it will be closer to the developing weakness (there already is a deep layer weakness present)

This should move much quicker than the EURO is suggesting. However, I can see this getting quite close to Haiti in about 36-48 hours.. I also expect to see some slowing soon once it moves to the longitude of the weakness

[Sanibel]

Watch for relocation!:

[Clipper96]

I'm skeptical of a relocation in this instance; I've seen this situation before. The big blow-up is in the maximum convergence section of the northern feeder band; this zone of best convergence will spiral inward toward the LLC provided the system remains unsheared.

....Now, to move to where the European has it at 168 hrs (over central Cuba) it would have to average only 4.6 kts forward speed from now until then. And the Euro doesn't have it near Haiti for 4 DAYS! At the speed it's moving now, that would be closer to 24 hrs, not 4 days.

The snail-crawler models are definitely out-to-lunch, but don't be surprised if proto-Gustav slows down once he's reach TS or Hurr. I've observed in the past that big storms over deep heat content just "eat" low-level steering as if it were so much extra fuel, exhibiting strange and contrary movement in the process (e.g., Katrina). What are speeds at 700mb?

Oh, and the last good position I got (2215Z) was about 13.8N/68.5W. Not a lot of surface obs nearby, but what few there are don't indicate any LLC yet.

That's quite reasonable; it's down the line from my earlier estimation of 13.5/67.5.

[KWT]

That does look pretty close, if it does relocate then on current track it clips Haiti however we shall see, I think this has a very good chance of developing though based on what its doing currently.

[Ed Mahmoud]

My gut is a Southern runner, but JB (just a very short post today, referring to the Canadian model., not certain what he was trying to say) has been implying a SE US threat for the holiday weekend.


I don't want to hazzard even an unofficial and amateur guesstimate yet since I don't think anyone knows for sure whether center develops (if it does) in area of maximum turning, or area of deepest convection.


If this is menacing the SE US next week, I'll be gone Saturday morning to Sunday afternoon. Florida Atlantic at Texas in Austin. Might be better than average out of conference season opener against small conference 'victim', as Schnellenberger has turned FAU into a winner very quickly. I hope the hotel has TWC. Poor substitute for S2K, but beggars can't be choosers.


Edit for spelling.

[KWT]

To be fair though Ed I think JB is keen for everything to head into the SE states this year from what I've seen!

Clipper96, I think we saw something similar (though a little different with pre Fay actually the MLC was with the best convergence and yet the LLC ended up doing the job.