ATL GUSTAV: Tropical Depression - Discussion

[KWT]

Yeah its very well developed this far east and the surface reports are really suggestive that there may also be an LLC, I think because of this NHC will hold for another 12-24hrs then upgrade, no reason to doubt a LLC based on the reports thus far.

[cheezyWXguy]

Yeah its very well developed this far east and the surface reports are really suggestive that there may also be an LLC, I think because of this NHC will hold for another 12-24hrs then upgrade, no reason to doubt a LLC based on the reports thus far.

The only reason I can see not to upgrade now is because it lacks very deep convection right now. But convection is on the increase and if there are reds in the core by the time we wake up tomorrow, I cant see why this wouldnt be a td in the morning and a ts in the afternoon.

[cycloneye]

The Latest:

[Weatherfreak000]

Definitely not quite a convincing argument yet...

[ConvergenceZone]

Yeah its very well developed this far east and the surface reports are really suggestive that there may also be an LLC, I think because of this NHC will hold for another 12-24hrs then upgrade, no reason to doubt a LLC based on the reports thus far.

The only reason I can see not to upgrade now is because it lacks very deep convection right now. But convection is on the increase and if there are reds in the core by the time we wake up tomorrow, I cant see why this wouldnt be a td in the morning and a ts in the afternoon.

I agree. I do see it developing, but we need to see some consistency with it and more convection...Even though I don't THINK it will be go *poof*, I've been fooled by these waves before...

[curtadams]

That is a big warp in the itcz, if its still attached. And if it can be considered a closed llc, I see no reason why they wont upgrade tomorrow morning after this develops some deep convection during dmax tonight.

It's very much still attached - you can see the ITCZ going off in both directions. And the circulation won't be closed until it does break the ITCZ - it will be like cyclonic rotation on a wave axis until then. You can see it in the Quickscat - winds to the south from the SW and to the north from the NE. But no NW or SE winds - just the NE and SW winds feeding into the ITCZ. Normally the back part wraps around first, followed by the front part a day or so later (if it develops, of course).

Incidentally, finding SW winds to the south of the ITCZ (like that ship did) means absolutely nothing, because that's the normal windflow S of the ITCZ and N of the equator. 95% of the time *any* point in the ITCZ during summer has NE winds to the N and SW winds to the S.

[cheezyWXguy]

Yeah its very well developed this far east and the surface reports are really suggestive that there may also be an LLC, I think because of this NHC will hold for another 12-24hrs then upgrade, no reason to doubt a LLC based on the reports thus far.

The only reason I can see not to upgrade now is because it lacks very deep convection right now. But convection is on the increase and if there are reds in the core by the time we wake up tomorrow, I cant see why this wouldnt be a td in the morning and a ts in the afternoon.

I agree. I do see it developing, but we need to see some consistency with it and more convection...Even though I don't THINK it will be go *poof*, I've been fooled by these waves before...

This one is different from the others. Many fool you into thinking it has a circulation by their curvature. However many dont have that and therefore, dont have a focus for convergence. This however, has evidence of a llc. The convergence associated with the circulation is already evidenced by the building of dots of deep oranges forming sporadically over the system. This combined with the dmax tonight should be enough to push this to tropical depression by tomorrow. I cant wait to see what the 8pm TWO says.

[cheezyWXguy]

That is a big warp in the itcz, if its still attached. And if it can be considered a closed llc, I see no reason why they wont upgrade tomorrow morning after this develops some deep convection during dmax tonight.

It's very much still attached - you can see the ITCZ going off in both directions. And the circulation won't be closed until it does break the ITCZ - it will be like cyclonic rotation on a wave axis until then. You can see it in the Quickscat - winds to the south from the SW and to the north from the NE. But no NW or SE winds - just the NE and SW winds feeding into the ITCZ. Normally the back part wraps around first, followed by the front part a day or so later (if it develops, of course).

Incidentally, finding SW winds to the south of the ITCZ (like that ship did) means absolutely nothing, because that's the normal windflow S of the ITCZ and N of the equator. 95% of the time *any* point in the ITCZ during summer has NE winds to the N and SW winds to the S.

Well, for one thing, there can be a closed circulation in the itcz...it is actually possible. Another thing, the last quikscat we have for this is several hours old I believe, and one more...there has been both a sw wind AND a west wind reported in the circulation. It wont take much to push this to td tomorrow as long as convection continues to increase overnight.

[HURAKAN]

Loop: http://rammb.cira.colostate.edu/ramsdis ... _floater_2

If you see the loop there's no question that it's developing. Nonetheless, persistance is the key.

[curtadams]

Another thing, the last quikscat we have for this is several hours old I believe, and one more...there has been both a sw wind AND a west wind reported in the circulation.

If it were at 15N, that would indicate a circulation. But in the ITCZ, SW + W winds need only a 45 degree bend in the ITCZ and that's nothing. Normally you see a detachment only after about a 135 degree bend or so.

[KWT]

Would think its only a matter of time before it breaks away from the ITCZ anyway and given the rotation with this system I find it quite likely something is going to come from this invest down the line.

[Derek Ortt]

there have been many depressions and storms in the EPAC embedded within the ITCZ

[cycloneye]

Ivan formed at 10n:

ZCZC MIATCPAT4 ALL
TTAA00 KNHC DDHHMM
BULLETIN
TROPICAL STORM IVAN ADVISORY NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM AST FRI SEP 03 2004

...IVAN FORMS OVER FAR EASTERN ATLANTIC...NINTH NAMED STORM OF THE
2004 SEASON...

AT 5 AM AST...0900Z...THE CENTER OF TROPICAL STORM
IVAN WAS LOCATED NEAR LATITUDE 10.0 NORTH...
LONGITUDE 30.7 WEST OR ABOUT 610 MILES... 985 KM...
SOUTHWEST OF THE CAPE VERDE ISLANDS.

[KWT]

Yeah I think the fact is we do have at the very least a pretty sharp trough at the low levels, if it holds like this and Dvorak estimates increase overnight then I think the NHC may just go for this.

[cycloneye]

Looks very good.

[KWT]

Yep does look very good indeed, let see what it looks like 12hrs time but it seems like its a TD right now IMO.

[Buck]

Good structure... it just needs convection to develope and persist and it should take off.

[cycloneye]

[jaxfladude]

Fay is first and foremost then Invest 94L, unless the NHC/TPPC thinks that it is a good idea to bring this up to a TD...they are the ones that call the shots.....
2 NHC/TPC!!!!

[ConvergenceZone]

Yep does look very good indeed, let see what it looks like 12hrs time but it seems like its a TD right now IMO.

Hey KWT, noticed you are in the UK....Not often we get someone that far away this interested in the tropics in this neck of the woods, kinda cool though...