99L Invest E of Windwards,Comments,Sat Pics,Models Thread #2

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Evil Jeremy
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#201 Postby Evil Jeremy » Sat Jul 29, 2006 7:28 am

I expect some type/kind of convection flare-up in the next 12-18 hours now.
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#202 Postby Emmett_Brown » Sat Jul 29, 2006 7:30 am

I don't see it either. I mean, you can see the swirl, but it is so feable looking... barely sustaining a popcorn cluster of storms... the only convergence is way out in front of this thing. This is another false alarm IMO... but i think we are getting close... maybe the next one develops...
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#203 Postby canetracker » Sat Jul 29, 2006 7:37 am

ThunderMate wrote:Are there any maps with model plots?


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#204 Postby storms in NC » Sat Jul 29, 2006 7:47 am

Well I will grant you that is is not the best I have seen. But now there is some to go on. It looked like it was try to pull some moister back in from the west when I was look at it about a hour ago
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#205 Postby knotimpaired » Sat Jul 29, 2006 7:52 am

Here on Vieques we have a steady rain but mid level....Not hard but not soft. You can go to our site http://www.playacofi.com, we have the only weather station on the island. It is a Weatherhawk 916.
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#206 Postby bvigal » Sat Jul 29, 2006 7:52 am

It looks to me like it's slowly organizing. The convection buildup can happen relatively quickly, and it is moving fast, hampering that process. NHC and TAFB both now agree on a low, it's on the surface mapsm both current and out to 72hrs.
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#207 Postby storms in NC » Sat Jul 29, 2006 7:56 am

what happen to the 18 MPH from last night? I know it is back up to 20 was there something it had to look at for a sec LOL
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#208 Postby Air Force Met » Sat Jul 29, 2006 7:57 am

Derek Ortt wrote:maybe I'm not seeing something (which could be as I'm about to head back to sleep for a few hours), but I am not seeing much organization at all with this feature. Atmosphere appears a little too stable based upon the inability to fire up convection


This is one time where the mets agree. I am not real impressed right now.

The BIG problem for this wave is the fact it has a convergent streamline to the southwest of it which is robbing it of a lot of energy....and will continue to do so. Plus...it looks like, because of the forward speed, it has some divergence out ahead of it.

It has great vorticity but until those two things change...it gonna be hard for the convection to sustain itself.
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#209 Postby Aquawind » Sat Jul 29, 2006 8:04 am

What is the convergent streamline going to do as the system progresses? Will it weaken, slowdown, continue out ahead of the system?
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#210 Postby bvigal » Sat Jul 29, 2006 8:13 am

What do these surface maps tell you? It's going to slow down, a lot!
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#211 Postby Air Force Met » Sat Jul 29, 2006 8:17 am

Aquawind wrote:What is the convergent streamline going to do as the system progresses? Will it weaken, slowdown, continue out ahead of the system?


I'm not sure, as I haven't looked at it enough. Convergent and divergent asymptotes are playing a big roll here though...and if I had my guess...it would be this...

IT should disappear in the next 36 hours or so as the southern part of the flow interacts with South America and if the wave can become more north-south oriented...instead of ENE-WSW oriented...like it is now.

See...the best vorticity is away from the greatest convergence. There is also some dry air to the south of it...with RH's in the mis-70's...which for the tropical oceans is pretty low.
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#212 Postby Aquawind » Sat Jul 29, 2006 8:20 am

Well the TAFB forecasts are a bit suspect in consistency imo. But yeah they show a low throughout this mornings set of maps. I agree with your statement above bvigal. As I do with AFM.. I am curious how the covergence streamline will interact in relation to the Low. It could weaken and the left over moisture along with less competeing convergence could enhance development.
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#213 Postby wxwatcher91 » Sat Jul 29, 2006 8:25 am

I dont think these have been posted yet... (sorry if they have been)
intensity is nothing remarkable right now but it is nice to see the locations...

DATE/TIME LAT LON CLASSIFICATION STORM
29/0545 UTC 8.5N 42.8W TOO WEAK 99L
28/2345 UTC 7.9N 40.5W TOO WEAK 99L
28/1745 UTC 8.1N 38.4W TOO WEAK 99L
28/1215 UTC 8.2N 36.6W TOO WEAK 99L
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#214 Postby Air Force Met » Sat Jul 29, 2006 8:25 am

bvigal wrote:What do these surface maps tell you? It's going to slow down, a lot!


I have to say I disagree with those maps. It is moving at 20 knots...and is all of the sudden gonna slow down to 3-4 knots?

1) Tropical waves don't move that slow...and
2) It is still under the Bermuda High...so how can it slow down?

Whoever drew those maps took the wave position off the GFS output. I went and checked the positions and matched them with the model.

The model is treating it like a stacked system...and since the 500mb flow is collapsing...it stalls it out.

However, waves don't go with the 500mb flow. They go with the lower level flow and the lower level flow is not going to change all that much over the next 3 days.

The analysist should have seen and thought of that. If this wave has only moved 4 degrees in the next 3 days...I'll shave my head and post the pics on the internet.
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#215 Postby Air Force Met » Sat Jul 29, 2006 8:28 am

Aquawind wrote:Well the TAFB forecasts are a bit suspect in consistency imo. But yeah they show a low throughout this mornings set of maps. I agree with your statement above bvigal. As I do with AFM.. I am curious how the covergence streamline will interact in relation to the Low. It could weaken and the left over moisture along with less competeing convergence could enhance development.


Well...the convergent asymptote is mostly the ITCZ/ET it is embedded in. It has to shake it. The way the streamlines are setup right now...all of the convergence is away from the low/vorticity center.

The only real way to change it is for the low to gain some latitude and for the pressure to lower a bit so that the convergence increases near it due to the pressure gradient increasing.
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#216 Postby Aquawind » Sat Jul 29, 2006 8:29 am

Convergence Analysis -- http://cimss.ssec.wisc.edu/tropic/real- ... 8conv.html

Divergence Analysis -- http://cimss.ssec.wisc.edu/tropic/real- ... g8dvg.html

Yep that's what it looks like AFM. I think is convergence streamline issue very important ATM.
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#217 Postby bvigal » Sat Jul 29, 2006 8:30 am

Aquawind wrote:.. I am curious how the covergence streamline will interact in relation to the Low. It could weaken and the left over moisture along with less competeing convergence could enhance development.

Good point. Seems to me the uncertainty is being handled by depiction of very slow development, i.e. 1mb drop each day to 1009 in 72hrs. Of course, we've all seen plenty of times where this just wasn't the case, and could drastically change in 12hrs. But this system does look like a slow developer.

Per the surface maps: They really have me scratching my head! Is it possible for a tropical wave to only move 2degrees in 24hrs? I can't remember ever seeing that.
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#218 Postby storms in NC » Sat Jul 29, 2006 8:31 am

Aquawind wrote:Well the TAFB forecasts are a bit suspect in consistency imo. But yeah they show a low throughout this mornings set of maps. I agree with your statement above bvigal. As I do with AFM.. I am curious how the covergence streamline will interact in relation to the Low. It could weaken and the left over moisture along with less competeing convergence could enhance development.


I don't know if this will help but here

http://www.asp.ucar.edu/colloquium/1998/hughw1.pdf
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#219 Postby wxman57 » Sat Jul 29, 2006 8:33 am

Air Force Met wrote:
Derek Ortt wrote:maybe I'm not seeing something (which could be as I'm about to head back to sleep for a few hours), but I am not seeing much organization at all with this feature. Atmosphere appears a little too stable based upon the inability to fire up convection


This is one time where the mets agree. I am not real impressed right now.

The BIG problem for this wave is the fact it has a convergent streamline to the southwest of it which is robbing it of a lot of energy....and will continue to do so. Plus...it looks like, because of the forward speed, it has some divergence out ahead of it.

It has great vorticity but until those two things change...it gonna be hard for the convection to sustain itself.


I'm in agreement with you two. It's a lot easier to see a lower to mid level spin when there's no convection any more. This thing is moving way too fast to develop. Heaviest convection is 300-500 miles (or more) west to west-southwest of the spin. That's not a good sign of imminent development.

The BAM models (GFS, too) have been pitiful at projecting this disturbance's movement. It hasn' tmoved any to the north in the last 2 days, and it's not showing any signs of a WNW or NW turn now. There's no reason the vorticity center won't follow the path of the convection that remains south of 10N out to 55W. I actually think either the extrapolated track or BAMD look the best for this disturbance. And there's a fair chance the spin will diminish or dissipate in the next day or so, with only an extended area of thunderstorms moving into South America.

One other thing, step back and look at the big picture of the tropics. Note the position of the ITCZ. It's like a sine wave, with a hump in the eastern Caribbean Sea associated with a wave there, and another hump around 20-25W. This disturbance is in the trough of the ITCZ. I've noticed in the past that such systems have a very difficult time developing, and they have a hard time moving northward.

Now I wouldn't completely write this system off, as it does have a pretty good vorticity center, but I think that chances of development appear to be diminishing at least over the next day or two.
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#220 Postby Stormavoider » Sat Jul 29, 2006 8:33 am

Air Force Met wrote:
bvigal wrote:What do these surface maps tell you? It's going to slow down, a lot!


I have to say I disagree with those maps. It is moving at 20 knots...and is all of the sudden gonna slow down to 3-4 knots?

1) Tropical waves don't move that slow...and
2) It is still under the Bermuda High...so how can it slow down?

Whoever drew those maps took the wave position off the GFS output. I went and checked the positions and matched them with the model.

The model is treating it like a stacked system...and since the 500mb flow is collapsing...it stalls it out.

However, waves don't go with the 500mb flow. They go with the lower level flow and the lower level flow is not going to change all that much over the next 3 days.

The analysist should have seen and thought of that. If this wave has only moved 4 degrees in the next 3 days...I'll shave my head and post the pics on the internet.


Starting with a military doo, that's a low stakes wager.
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