ATL: INVEST 90L - Discussion

[Gustywind]

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 06 2014

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 28W FROM 18N SOUTHWARD.
A 1010 MB LOW PRESSURE CENTER IS ALONG THE WAVE NEAR 14N. THE
WAVE IS MOVING WESTWARD 15 KNOTS. CONVECTIVE PRECIPITATION...
NUMEROUS STRONG FROM SCATTERED TO NUMEROUS STRONG FROM 13N TO
17N BETWEEN 29W AND 31W

[ronjon]

Looks like a depression already this morning. NHC odds look a bit low at the moment.

[tropicwatch]

It does look pretty good this morning.

[USTropics]

I'm surprised by this one, considering the plume of dry air directly in front of 90L that you can see on this loop: http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?wv_east_enhanced+12

It's doing a good job of getting a bit of moisture out in front though, and it has maintained a decent vorticty maximum the past couple of days (in fact, it's not as elongated at the 850mb level this morning). Let's see if it can maintain until 45-50W, where the dry air starts to abate.

[SFLcane]

If this develops it may be a problem down the road but that's a big IF at this point with all this dry air.

[blp]

The TPW looks real good at the moment. This certainly merits higher than 10%

http://tropic.ssec.wisc.edu/real-time/mimic-tpw/natl/anim/latest72hrs.gif

[AEWspotter]

If they are analyzing a surface low with this disturbance (which there is strong evidence of on VIS), I'd be tempted to classify it as a TD. Convection has been persistent and an MCV appears to be forming within those deep clouds to the north of the estimated LLC (not sure how to tell if it's actually closed). I assume the MCV and surface low will do a little dance and line up today. The question, of course, if whether or not convection will persist. I know the environment ahead of this system is dry and stable, but that doesn't change the fact RIGHT NOW, it's embedded within a very moist environment, warm SSTs, and 8kts of shear.

I know it's annoying to start running guidance on a system that might have only a short lifetime for the time being (I still think 90L will have it's best chance near 55W), but I think NHC is being the game on this one...

[SFLcane]

If they are analyzing a surface low with this disturbance (which there is strong evidence of on VIS), I'd be tempted to classify it as a TD. Convection has been persistent and an MCV appears to be forming within those deep clouds to the north of the estimated LLC (not sure how to tell if it's actually closed). I assume the MCV and surface low will do a little dance and line up today. The question, of course, if whether or not convection will persist. I know the environment ahead of this system is dry and stable, but that doesn't change the fact RIGHT NOW, it's embedded within a very moist environment, warm SSTs, and 8kts of shear.

I know it's annoying to start running guidance on a system that might have only a short lifetime for the time being (I still think 90L will have it's best chance near 55W), but I think NHC is being the game on this one...

Could be the sleeper of the year but we shall see. Honestly iam surprised with most recent flare up with dry airmass intrained in circulation. No models ran 12z

[AEWspotter]

I just created this loop at the CIRA RAMMB web site. It is a large-scale visible image every hour on the hour since 9/5, 20Z. That, my friends, is a tropical depression:

CIRA VISIBLE LOOP

[cycloneye]

I would raise the % to 30 at 2.

[floridasun78]

I just created this loop at the CIRA RAMMB web site. It is a large-scale visible image every hour on the hour since 9/5, 20Z. That, my friends, is a tropical depression:

CIRA VISIBLE LOOP

do it look like their shear over 90l area low at expose to south of storm area i look at Visible Loop you see it here link http://www.ssd.noaa.gov/goes/east/tatl/flash-vis.html far been td

[AEWspotter]

If they are analyzing a surface low with this disturbance (which there is strong evidence of on VIS), I'd be tempted to classify it as a TD. Convection has been persistent and an MCV appears to be forming within those deep clouds to the north of the estimated LLC (not sure how to tell if it's actually closed). I assume the MCV and surface low will do a little dance and line up today. The question, of course, if whether or not convection will persist. I know the environment ahead of this system is dry and stable, but that doesn't change the fact RIGHT NOW, it's embedded within a very moist environment, warm SSTs, and 8kts of shear.

I know it's annoying to start running guidance on a system that might have only a short lifetime for the time being (I still think 90L will have it's best chance near 55W), but I think NHC is being the game on this one...

Could be the sleeper of the year but we shall see. Honestly iam surprised with most recent flare up with dry airmass intrained in circulation. No models ran 12z

The system stayed remains close enough to the ITCZ so that it can resupply it's moisture. This is a much different setup than last year, when all of the low-level convergence was weak and positioned further south (some say linked to anomalously warm SSTs on the south side of equator in the Atlantic). As long as the system has a moisture supply, then it should be able to overcome the dry air. I guess we'll have to wait and see if it pulls away from this moisture source entirely. Anyway, check out this TPW loop and you'll see how AL06, I mean 90L, has kept contact with the ITCZ moisture.

http://rammb.cira.colostate.edu/products/tc_realtime/loop.asp?product=16kmtpwp&storm_identifier=AL902014&starting_image=2014AL90_16KMTPWP_201409041945.GIF

[floridasun78]

I would raise the % to 30 at 2.

nhc may drop % 0 or keep it 10%

[AEWspotter]

I just created this loop at the CIRA RAMMB web site. It is a large-scale visible image every hour on the hour since 9/5, 20Z. That, my friends, is a tropical depression:

CIRA VISIBLE LOOP

do it look like their shear over 90l area low at expose to south of storm area i look at Visible Loop you see it here link http://www.ssd.noaa.gov/goes/east/tatl/flash-vis.html far been td

The shear was analyzed at 8kts out of the southeast at 6Z, so that could have some reason for the northward displacement of convection. But, I suspect the system is still a little disorganized and maybe the LLC will be pulled up under the convection. I think I can already see that happening on the VIS.

[gatorcane]

Deep convection on the increase again, latest saved image below. AEWspotter, you called this yesterday doubting that the dry air would really kill this thing. NHC is too low on development chances at 10%.

[floridasun78]

I just created this loop at the CIRA RAMMB web site. It is a large-scale visible image every hour on the hour since 9/5, 20Z. That, my friends, is a tropical depression:

CIRA VISIBLE LOOP

do it look like their shear over 90l area low at expose to south of storm area i look at Visible Loop you see it here link http://www.ssd.noaa.gov/goes/east/tatl/flash-vis.html far been td

The shear was analyzed at 8kts out of the southeast at 6Z, so that could have some reason for the northward displacement of convection. But, I suspect the system is still a little disorganized and maybe the LLC will be pulled up under the convection. I think I can already see that happening on the VIS.

ok let see nhc say 2pm

[floridasun78]

Deep convection on the increase again, latest saved image below. AEWspotter, you called this yesterday doubting that the dry air would really kill this thing. NHC is too low on development chances at 10%.

gator look at Visible Loop you see low exose south of storm it now been shear a bit i think nhc keep it 10% or drop to 0% at 2pm

[AEWspotter]

Deep convection on the increase again, latest saved image below. AEWspotter, you called this yesterday doubting that the dry air would really kill this thing. NHC is too low on development chances at 10%.

I just can't remember ITCZ actually aiding the development of an easterly wave as it came off the coast in the last few years. So I got excited...

[gatorcane]

Looks like if it can make it to about 45W, the moisture starts to increase as can be seen by the wide WV image below. In fact look how moist it is over the SW Atlantic, Gulf, and Caribbean. I am not sure why the GFS is not developing this once it gets further west. It looks like there could be some westerly shear as it approaches the Leewards but doesn't look too bad.

[Riptide]

One thing i've learned over the years is that shear vectors and speeds change constantly, even in the short-term. There so many variables at play. Could possibly find a nice environment down the road.