ATL: FOUR - Remnants - Discussion

[MississippiWx]

Visible (veggie band 3) loop:

http://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=full_disk&x=18944&y=8012&z=4&im=12&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&p%5B0%5D=2&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&s=rammb-slider

Explanation of the GOES 16 channels or bands: http://www.goes-r.gov/education/ABI-bands-quick-info.html

Check out the low level clouds to the south and east of TD4 and then the low clouds to the north and west. Low level divergence, anyone? Yuck. Not good for the system when the air around it is moving away from it.

[TheStormExpert]

 https://twitter.com/mjventrice/status/883030181878931458

[GCANE]

Nice little circulation around 13.4N 44.8W.
If that's the case, would put it south and west of the forecast points.
A weaker system would tend to pull it more west and less north than what the models maybe forecasting.

[wxman57]

Nice little circulation around 13.4N 44.8W.
If that's the case, would put it south and west of the forecast points.
A weaker system would tend to pull it more west and less north than what the models maybe forecasting.

I see what looks like a MLC near 12.5N/44W. LLC may not exist, or it is still east of 44W (or elongated). Looks like it has degenerated to a remnant low or wave.

[GCANE]

Nice little circulation around 13.4N 44.8W.
If that's the case, would put it south and west of the forecast points.
A weaker system would tend to pull it more west and less north than what the models maybe forecasting.

I see what looks like a MLC near 12.5N/44W. LLC may not exist, or it is still east of 44W (or elongated). Looks like it has degenerated to a remnant low or wave.

I saw that one too.
Cumulus cloud-top rotation is what I am seeing at 13.4N 44.8W.

[GCANE]

Looks like that's going to be a naked swirl a lot farther south than forecast track.
More moist low-level air to work with down the road and much farther away from the TUTT shredder.

[Siker]

12z UKMET sends this into Jacksonville as a strong TS.

[tiger_deF]

I think everyone here is writing off 94L too early. Granted, I am not a wishcaster thinks it will be anything more than a weak tropical storm, but while the convection is in the process of collapsing the overall swirl of the system has grown marginally better over the past 3 hours. It appears to be continuing rotation on the GEOS loop, and on earth.nullschool the circulation has gradually become more circular in nature.

[cycloneye]

BULLETIN
Tropical Depression Four Advisory Number 4
NWS National Hurricane Center Miami FL AL042017
500 PM AST Thu Jul 06 2017

...DEPRESSION ACCELERATING WESTWARD AND STILL NOT VERY WELL
ORGANIZED...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...13.1N 44.9W
ABOUT 1110 MI...1785 KM E OF THE LESSER ANTILLES
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES



Tropical Depression Four Discussion Number 4
NWS National Hurricane Center Miami FL AL042017
500 PM AST Thu Jul 06 2017

It's difficult to tell from visible and microwave satellite imagery
whether or not the depression still has a closed surface
circulation. In addition, the forward speed is now about 20 kt,
which would make it difficult for a 25-kt depression to maintain
westerly winds to the south of the center. For now, advisories
will be maintained until/if there is stronger evidence that the
circulation has opened up.

Convective cloud tops have warmed during the past few hours, and
Dvorak final-T numbers from TAFB and SAB have decreased. Therefore,
the initial intensity will be held at 25 kt based on continuity.
Multispectral satellite imagery shows the Saharan Air Layer is
overtaking the depression, and it will be increasingly more
difficult for the system to maintain organized deep convection. It
has also become more likely that the cyclone will not strengthen
beyond its current intensity. The global models indicate that
southwesterly to westerly deep-layer shear will increase in about 36
hours, at which point the NHC official forecast now shows the
depression degenerating to a remnant low. However, it's entirely
possible that the cyclone could open up into a tropical wave at any
time.

Based on the estimated center location, the depression has not
gained much latitude today, and the initial motion estimate is
275/20 kt. The global models remain persistent that the cyclone
should turn west-northwestward in about 24 hours as it approaches a
break in the subtropical ridge, and they are generally in very close
agreement on the future track and forward speed through at least 48
hours. The updated NHC track forecast is nudged southward to
account for the recent motion, but otherwise it is an update of the
previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 13.1N 44.9W 25 KT 30 MPH
12H 07/0600Z 13.8N 47.8W 25 KT 30 MPH
24H 07/1800Z 14.9N 51.5W 25 KT 30 MPH
36H 08/0600Z 16.2N 55.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 08/1800Z 17.8N 58.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 09/1800Z 20.9N 64.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 10/1800Z...DISSIPATED

$$
Forecaster Berg

[GCANE]

Perhaps this is a good bit of speculation; but, if the latest 85GHz Donut Hole is any indication of a CoC that would put it at 13.1N 44.9W @ 1906Z.

Second snip below marks the spot with a red X.
Well south and faster than the forecast track depicted by the red line.

[tropicwatch]

Well that is the last position given by NHC.

[Emmett_Brown]

And now... we wait for the nightly blow up. Will it happen again... or is it toast?

[Hammy]

Looks like there's nothing left of a circulation at the moment. Quite a bit of spin, but the winds to the east are either out of the northwest or northeast--no southwesterly winds.

[Sciencerocks]

Looks like there's nothing left of a circulation at the moment. Quite a bit of spin, but the winds to the east are either out of the northwest or northeast--no southwesterly winds.

This is exactly what I see too Hammy. Also include the ascat wind sat that shown no closed circulation earlier today and the lower level clouds to the south of the circ doesn't give off the idea that it is closed either. I believe it will "likely be downgraded.

[smithtim]

Crap model is going to be crap most of the time. This is why you should never trust the GFS unless the ECMWF is on board as well.

The GFS is a world-class model that drives changes in the global economy every morning as it runs. It is only slightly worse than the Euro in the long run. You can call out the busts, but don't call it crap. A lot of very smart people have put in hundreds of thousands of hours of hard work to make that model what it is today.

This is very true and very well spoken...as someone who does academic research for a living I can definitely relate to how much work goes into any scientific problem. Also, I am very grateful for all the work that has been done and amazed at how far these things have come over last couple of decades!!!

BTW for anyone who knows the inner workings of these models will remember that many things within the models are determined as solutions of PDEs which are very very sensitive to small changes in the initial value conditions! And as said a few posts back really can't trust those IVCs until fed solid data, recon etc

[Sciencerocks]

Sab numbers are 1.0/1.5
06/2245 UTC 12.5N 45.0W T1.0/1.5 04L -- Atlantic

[Ntxw]

With the sun down, skeletons are left

[alienstorm]

The point here is that it's July 7 and we already had 2 MDR systems with a potential 3 on the horizon. Come August and Sept we will be having a new one every week.

[Digital-TC-Chaser]

12z UKMET sends this into Jacksonville as a strong TS.

Its not dropping it so far.As for strength ?

[Hammy]

I checked the ASCAT and this is a really bizarre setup--it's quite odd to see the winds flowing out the eastern side to the SE, normally in an open wave situation its out of the east and an up-and-over flow. It almost seems like the system has been absorbed back into the ITCZ while pulling it significantly further north than usual. Could this have any implications for later in the season as far as seeing more WPac-type monsoonal storms form in the MDR?