ATL GUSTAV: Tropical Depression - Discussion

[deltadog03]

Hmmm...I guess I am not seeing the motion correctly...Still looks around 285 ish..

[KWT]

I don't think its that far to the north Derek, I'd only guess 285 maybe but without a good center fix its pretty tough to call, where would you place the 'center'

To clear Hispaniola totally, it needs to go past 15N really before 69W.

[jlauderdal]

Hmmm...I guess I am not seeing the motion correctly...Still looks around 285 ish..

you guys must be using two different centers which is fine since we dont have an official center so you are both right

[jlauderdal]

Miami AFD-back 2.0+ PWATS for us, well it was nice for the last few days but that will change

TAFB ANALYZES A TROPICAL WAVE OVER THE CARIBBEAN WITH THE NORTHERN
EXTENSION UP TO HISPANIOLA. GFS SHOWS INCREASING MOISTURE ACROSS
MAINLAND SOUTH FL ON TUESDAY...OFF THE NORTHERN EXTENSION OF THIS
WAVE...WITH PWATS ON TUESDAY RANGING FROM AROUND 2 INCHES AT THE
LAKE TO 2.3 INCHES AT MIAMI. DECIDED TO BLANKET CHANCE POPS
EVERYWHERE TUE...AS THIS INCREASING MOISTURE COULD SPREAD
SHRA/TSRA JUST ABOUT ANYWHERE.

DID NOT CHANGE THE FCST FOR MID WEEK AND BEYOND. INHERITED NEAR
CLIMO POPS LOOK GOOD FOR NOW WITH TYPICAL DIURNAL CONVECTION
EXPECTED. HOWEVER...THE ONLY FLY IN THE OINTMENT WOULD BE TO SEE
WHAT...IF ANYTHING...DEVELOPS FROM THE AREA OF DISTURBED WEATHER
OVER THE SOUTHEAST CARIB BEING MONITORED FOR POSSIBLE DEVELOPMENT
BY NHC.

[dixiebreeze]

24/1745 UTC 13.0N 66.0W T1.5/1.5 94L -- Atlantic Ocean

[Aric Dunn]

decent at the mid levels

however, the farther north it goes, the greater the shear. I fail to understand why the GFS is missing the shear, as evidenced by the SHIPS analysis

one other note, about the NHC TWO. I have seen many people think here that orange means development is expected. Quick math lesson. 100%-20 to 50 yields a 50-50% chance that development will NOT occur. Orange does not indicate development is expected

its is very possible that the ships analysis is over estimating the shear..
current shear analysis has an upper ridge developing over the system with no foreseeable shear unless it reaches Hispaniola and even the the shear axis more north of there. from Jamaica extending west to the entire western carribean upper level conditions are at the least marginal to good.

[cpdaman]

it is difficult IMO to determine a exact track when the storm is still expanding/center still "maturing

i see what derek is talking about but the TWO calls for w or wnw motion so something has to give

i place this thing from eyeballing it on the nhc visible loop (thru 1945) to be around 13.6 N 66.7 W already and moving pretty swiftly (20 mph'ish)

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

not sure if this NW motion is due to the center still developing/maturing which provides the appearance of a NW motion or a more long term NW motion. on the cimss site steering on any layer (500 -850) or 200-700 shows WNW motion of about 285-290 so i would not be suprised to see this motion resume once the storm's center is a bit more mature

[deltadog03]

Right, at this point it is tough to get a really good track, but I see atleast a very nice MLC pushing around 285...We shall see...

[KWT]

cpdaman, yeah I'd put it close to there, maybe just a little to the Sw of that location but the general motion still seems to be around WNW. Stil as you say without a proper center at the surface its tough to say...

[Aric Dunn]

radar site is only about 75 to 100 miles out and there is a pretty clear circulation, as for being at the surface is still yet to be seen, but there are some signs this is taking place with the increased banding features on satellite( weak) ...
http://www.weather.an/product_images/hi ... color.html

[AJC3]

Keep in mind this system is still a SW-NE oriented wave with a low embedded along the wave axis. Hence, the low/vort center can very easily slide northward along the axis and tighten up into a primary center - in fact it appears that it may be doing just that. So even if you assume a motion more toward 280-285, the northward propagation can yield a motion closer to 295-300.

[Dean4Storms]

I'm not putting a great deal of faith in the global models yet on this sytem. They had Fay tracking north of PR and then developing over Eastern Cuba/S. Bahamas and heading North up off the east coast of FL before Fay actually developed a LLC at about the stage 94L is at now. It wasn't until Fay actually developed into a TC that the models began to get some close idea of what she ultimately would do.

[cheezyWXguy]

Keep in mind this system is still a SW-NE oriented wave with a low embedded along the wave axis. Hence, the low/vort center can very easily slide northward along the axis and tighten up into a primary center - in fact it appears that it may be doing just that. So even if you assume a motion more toward 280-285, the northward propagation can yield a motion closer to 295-300.

Yes but if that is the case, then the northward propogation would likely end when the center tightens up and the low becomes its own entity as a tropical cyclone, thus it would resume a 280-285motion. In this case, I still dont see a DR/Haiti threat. More likely a Jamaica or Cuba hit, eventually leading into the GOM. I just cannot see it going much further east than that. Correct me if Im wrong.

[KWT]

AJC3, yeah I can see what you mean, its pretty obvious on the images right now with convection flaring up along that wave axis, with the MLC heading WNW.

I think this will come close to Haiti but its hard to say right now, I actually think it will then bend back.

[Meso]

A storm with lots of moisture surrounding it, been a lack of those lately

[Sean in New Orleans]

I'm not putting a great deal of faith in the global models yet on this sytem. They had Fay tracking north of PR and then developing over Eastern Cuba/S. Bahamas and heading North up off the east coast of FL before Fay actually developed a LLC at about the stage 94L is at now. It wasn't until Fay actually developed into a TC that the models began to get some close idea of what she ultimately would do.

Me either, at this point. The steering patterns right now are clearly too complicated for the models to get a handle. Seems like it's time to sit down and enter some more data to get the models more reliable when things are complex.

[AJC3]

Keep in mind this system is still a SW-NE oriented wave with a low embedded along the wave axis. Hence, the low/vort center can very easily slide northward along the axis and tighten up into a primary center - in fact it appears that it may be doing just that. So even if you assume a motion more toward 280-285, the northward propagation can yield a motion closer to 295-300.

Yes but if that is the case, then the northward propogation would likely end when the center tightens up and the low becomes its own entity as a tropical cyclone, thus it would resume a 280-285motion. In this case, I still dont see a DR/Haiti threat. More likely a Jamaica or Cuba hit, eventually leading into the GOM. I just cannot see it going much further east than that. Correct me if Im wrong.

What you say is true, assuming that the steering patterns don't change - i.e. more of a weakness develops farther north near Hispanola (70-75W) over the next couple days. My point was directed more toward what has been going on today, and what may continue to happen in the short term.

[jlauderdal]

Keep in mind this system is still a SW-NE oriented wave with a low embedded along the wave axis. Hence, the low/vort center can very easily slide northward along the axis and tighten up into a primary center - in fact it appears that it may be doing just that. So even if you assume a motion more toward 280-285, the northward propagation can yield a motion closer to 295-300.

Yes but if that is the case, then the northward propogation would likely end when the center tightens up and the low becomes its own entity as a tropical cyclone, thus it would resume a 280-285motion. In this case, I still dont see a DR/Haiti threat. More likely a Jamaica or Cuba hit, eventually leading into the GOM. I just cannot see it going much further east than that. Correct me if Im wrong.

wait a second, you dont know when that low AJC3 talks about becomes a primary center and when and if it does the flow could be such that it goes 300 or 310, its all about timing, you cant assume that when and if it does get a primary center that it will go 280-285, if you can be sure and prove than NHC has a job for you...

[Tropicswatcher]

It's looking like we (Puerto Rico) are going to get some rain from this system!

[cheezyWXguy]

Keep in mind this system is still a SW-NE oriented wave with a low embedded along the wave axis. Hence, the low/vort center can very easily slide northward along the axis and tighten up into a primary center - in fact it appears that it may be doing just that. So even if you assume a motion more toward 280-285, the northward propagation can yield a motion closer to 295-300.

Yes but if that is the case, then the northward propogation would likely end when the center tightens up and the low becomes its own entity as a tropical cyclone, thus it would resume a 280-285motion. In this case, I still dont see a DR/Haiti threat. More likely a Jamaica or Cuba hit, eventually leading into the GOM. I just cannot see it going much further east than that. Correct me if Im wrong.

What you say is true, assuming that the steering patterns don't change - i.e. more of a weakness develops farther north near Hispanola (70-75W) over the next couple days. My point was directed more toward what has been going on today, and what may continue to happen in the short term.

What is creating the weakness that would take it to the DR in the first place? Is it the that trough up there? If it is, it seems like 94L is outrunning it, and the only weakness I see after that, that could pull it north is the weakness left behind by Fay in the northern gulf...which is not good if you dont want a northern gulf landfall. Nothing certain, but it must be taken into consideration.