ATL: INVEST 90L - Discussion

[AEWspotter]

6Z SHIPS says that the shear will increase to above 25kts in 72 hours. So if it takes advantage of its presently favorable conditions (SST, wind shear) and develops quickly, it might be able to deal with that trailing westerly shear associated with cold low. Models are notoriously bad at dealing with cold lows, but I think it's the cold low digging near 55W that is going to be the main player with shear. Obviously, if it stays weak or unorganized, that shear will tear it apart. Of course, shear forecasts change all of the time so let's see what it says when we are 24 hours out.

http://www.ral.ucar.edu/hurricanes/realtime/plots/northatlantic/2014/al902014/stext/14090606AL9014_ships.txt

[TheStormExpert]

Not all that bad looking ATM, though that could all change in a flash like we've seen way too many times this season and last.

[gatorcane]

NHC won't bite but note underlined part

Shower activity associated with an area of low pressure located
several hundred miles west of the Cape Verde Islands shows some
signs of organization. However, this system is moving into an
unfavorable environment during the next several days, and
development is not anticipated.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...10 percent.

[floridasun78]

going dead zone for tropical wave so % may go 0 by sunday

[Alyono]

I wonder how things would be different if we had an independent agency classifying the systems, and NHC only forecast the systems

[floridasun78]

I wonder how things would be different if we had an independent agency classifying the systems, and NHC only forecast the systems

nhc doing good job with classifying the systems

[Sanibel]

Better organization for the time being.

[AEWspotter]

This is exactly the type of system that is difficult to forecast, given the position of the cold lows and the obvious dry air ahead of the system. It's hard to say how this system will look in 72 hours, and the models are bouncing around run to run. Sounds like the type of system that could hurt forecast skill statistics for NHC at the end of the season... Just sayin...

If they don't classify it now and it tuckers out, then they will almost certainly add it in the postseason analysis. Just my opinion.

[cycloneye]

2 PM TWD:

TROPICAL WAVE EXTENDS FROM 10N30W TO 20N30W MOVING W AT 15-20
KT. A 1012 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 14N THAT
REMAINS LARGELY EMBEDDED WITHIN THE MONSOON TROUGH AXIS. THE
WAVE COINCIDES WITH A HIGH AMPLITUDE 700 MB TROUGH BETWEEN 26W-
38W AND A 850 MB RELATIVE VORTICITY MAXIMUM IN THE VICINITY OF
15N30W. SCATTERED MODERATE CONVECTION IS FROM 14N-18N BETWEEN
30W-33W.

[cycloneye]

18z Best Track: Latitude position is more to the central convection.

AL, 90, 2014090618, , BEST, 0, 153N, 320W, 25, 1009, DB

[Nimbus]

With all that dry air practically any shear at all would disrupt that central circulation that we are seeing.
Looking at this system as it passes 33w it does look better organized than most of the prior invests.
The higher latitude track means it can't draw as much moist heat energy from the ITCZ like the other systems did.

Looks like it is heading more w or even wwsw now and some of the energy we are seeing could be enough to regenerate this into a storm west of 50w.

[gatorcane]

It almost looks like it may be trying to develop some banding features looking at this loop (towards the end of the loop) plus I am seeing some nice outflow starting to develop. I think one could argue this has been a tropical depression for the past several hours. Convection still holding together despite DMIN:

http://rammb.cira.colostate.edu/ramsdis ... display=12

[Siker]

It almost looks like it may be trying to develop some banding features looking at this loop (towards the end of the loop) plus I am seeing some nice outflow starting to develop. I think one could argue this has been a tropical depression for the past several hours. Convection still holding together despite DMIN:

http://rammb.cira.colostate.edu/ramsdis ... display=12

Agreed. I'm not trained in recognizing banding, it might just be a gap in convection, but I definitely agree that it's got a nice structure right now.

[AEWspotter]

Definitely a TD, and with the banding it could be more. There is no way they can't acknowledge it if it stays together through the diurnal max tonight (which I believe it will).

Of course, ASCAT keeps missing the storm, so there is no definitive loop at what the low-level winds are like. This is why we need more scatterometers looking down from the sky. It would be so worthwhile (and probably not too expensive) to employ like 10 scatterometer satellites to provide global coverage at 3-6 hour resolution. It would be amazing for global model initialization and would allow for consistent looks at low-level features. Of course, if METOP-A and METOP-B were actually staggered so that they didn't overlap passes, we'd already have pretty good coverage. Instead, B pretty much mimicks the pass of A a few hours after, for validation. To me, that's wasted resources.

[AEWspotter]

It almost looks like it may be trying to develop some banding features looking at this loop (towards the end of the loop) plus I am seeing some nice outflow starting to develop. I think one could argue this has been a tropical depression for the past several hours. Convection still holding together despite DMIN:

http://rammb.cira.colostate.edu/ramsdis ... display=12

Agreed. I'm not trained in recognizing banding, it might just be a gap in convection, but I definitely agree that it's got a nice structure right now.

Banding or not, the outflow is surprisingly symmetric at the present time!

[Alyono]

I'm not willing to say this is a TD right now as there is no definitive proof of a closed surface circulation (it may very well be, however).

However, development chances appear quite a bit higher than 10%. More like 50 at the moment. Wouldn't take much to get this to be a TD

[SFLcane]

Coming into view... Again i'am still puzzled how this has sustained convection thus far.

[Nimbus]

Looks like it has had a high sitting over it since it came off the coast of Africa.
A small relatively well stacked system can maintain in that kind of environment.
The rain from the CDO feeds back moisture.

Of course it can't be stacked unless its at least a depression so...

[sunnyday]

Isn't this one likely to go the way of the others this season? If not, please explain.
Thank you....

[Hammy]

I'm not willing to say this is a TD right now as there is no definitive proof of a closed surface circulation (it may very well be, however).

However, development chances appear quite a bit higher than 10%. More like 50 at the moment. Wouldn't take much to get this to be a TD

This is likely one of those times that an ASCAT pass will be the deciding factor, as it does look much better organized than yesterday, and there are definite signs that a circulation may in fact be forming on the SE edge of the convection, but it's not clear enough to tell whether it's closed just from cloud motion.