Tropical Wave ESE of Lesser Antilles (Is INVEST 99L)

[SconnieCane]

It's at a pretty low latitude. Any thoughts this could try to pull a Harvey? Not suggesting a similar outcome is likely, but in the general sense of develop just enough to get named, open back up into a wave when it hits unfavorable conditions, but hang on just enough to spin back up into a potentially potent homebrew when it reaches bathwater in the Gulf.

New member btw, but guest lurker since last year's incredible Atlantic season. As you can probably tell from my name I live somewhere far removed from any threat of tropical cyclone impacts, but have been fascinated by them since childhood in the '90s after watching the documentaries on Andrew and Hugo along with John Hope's Tropical Updates on TWC.

[lrak]

Welcome SconnieCane I love this board. I've learned so much about the weather from these brainiacs

[gatorcane]

1. A disorganized area of showers and thunderstorms is located about
midway between Africa and the Lesser Antilles. Some gradual
development of this system is possible through early next week as it
moves slowly westward.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

[gatorcane]

Floater being moved to the area:

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

[AutoPenalti]

1. A disorganized area of showers and thunderstorms is located about
midway between Africa and the Lesser Antilles. Some gradual
development of this system is possible through early next week as it
moves slowly westward.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

[img]https://s8.postimg.cc/m1jpmz6ol/two_atl_5d1.png

Looks like the little "unfavorable upper level winds" snippet was completely removed.

[AnnularCane]

I wonder if they think any unfavorable wind conditions will improve?

[gatorcane]

I wonder if they think any unfavorable wind conditions will improve?

The GFS now shows favorable upper-level winds through the 5 day forecast period. For example here is day 5 and you can see the anticyclonic flow east of the Lesser Antilles. Seems a small anticyclone will build over the system and move west in tandem with it:

[NotSparta]

I wonder if they think any unfavorable wind conditions will improve?

The GFS now shows favorable upper-level winds through the 5 day forecast period. For example here is day 5 and you can see the anticyclonic flow east of the Lesser Antilles. Seems a small anticyclone will build over the system and move west in tandem with it:

ig]https://s8.postimg.cc/ds7u8zd2t/gfs_shear_eatl_21.png[/img]

Not sure if this would effect the system, but the GFS & GEFS build an anticyclone where the TUTT has been reigning in about a week

 https://twitter.com/pppapin/status/1028067437944627201

[Nimbus]

These low latitude systems that feed off the ITCZ are hard to predict till we get a clear circulation center. Should stay south initially as it approaches the eastern periphery of the high so might be a Caribbean runner. Interesting the pro mets are taking notice.

[cycloneye]

1. A disorganized area of showers and thunderstorms is located about
midway between Africa and the Lesser Antilles. Some slight
development of this disturbance is possible during the next day or
two while it remains nearly stationary.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...10 percent.

[cycloneye]

1. A disorganized area of showers and thunderstorms is located about
midway between Africa and the Lesser Antilles. Some slight
development of this disturbance is possible during the next day or
two while it remains nearly stationary.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...10 percent.

[AutoPenalti]

Interesting that now it’s scaled down to 10% in the next 5 days but does not mention unfavorable conditions.

[Hurricaneman]

Interesting that now it’s scaled down to 10% in the next 5 days but does not mention unfavorable conditions.

Might be like with Beryl where they didn’t raise the chances until development was evident

[SootyTern]

or maybe because it is stationary and won't be moving into better conditions anytime soon

[AnnularCane]

Is it normal for an MDR disturbance to just go stationary like that?

[gatorcane]

The GFS is developing this on the EPAC side in the long-range.

[cycloneye]

1. A weak area of low pressure located about midway between the west
coast of Africa and the Lesser Antilles is producing a minimal
amount of showers and thunderstorms. Significant development of
this system appears unlikely, due to unfavorable environmental
conditions, while it moves slowly westward during the next couple of
days.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...10 percent.

[AJC3]

Is it normal for an MDR disturbance to just go stationary like that?

It's not what usually occurs, since most African Easterly Waves (AEW) are embedded in the (AEJ) African Easterly Jet, which typically moves them along toward the west at about 5 degrees per day. For reference, 1 degree LON in the MDR is about 67-68 statute miles, so 5 degrees per day works out to 335-340 miles in 24 hours, or not quite 15 MPH.

The AEJ has seasonal changes in strength and position (weaker & moves northward APR-AUG/stronger & moves southward from SEP onward). When/if the AEJ is particularly strong in some parts of the MDR, then waves will move faster, with forward speeds sometimes as high as 20-25 MPH. On the other hand, when it is slows and/or shifts northward, the ITCZ/monsoon trough can expand northward into the MDR. Waves that move into this area will slow down and often combine with preexisting convergence/vorticity to produce a large area of thunderstorms.

When an active monsoon trough breaks down, you can get an outbreak of TCs, although this usually happens in the other TC basins - the NIO, SIO, WPAC (where an outbreak recently took place), CPAC, EPAC, and SPAC. In these basins, TC genesis via the monsoon trough is the norm, rather than the exception, as opposed to the ATLC. In fact, if you look at global TC genesis as a whole, you'll find that the ATLC really is the oddball basin of the group.

Probably a longer answer than you wanted - the short answer is "no". lol

[stormzilla]

Just noticed in the wave 43/44w at the end of the frame there is some lower level spin so upon checking https://earth.nullschool.net/#current/w ... .058,6.475 you can that the spin is all the way up to 850.

Here`s what it looks like on GOES-16 https://col.st/iTB7p

https://www.tropicaltidbits.com/sat/sat ... =truecolor

[gatorcane]

There is nothing else going on in the MDR but it might be worth watching this wave that has flared up overnight given we are at the time of year waves need to be watched closely. The Euro and CMC models develop a small area of 850mb vorticity out of this and notice the GFS builds a large anticyclone over the Eastern Caribbean / Lesser Antilles by days 3 and 4:

Floater loop shows some spin:
http://rammb.cira.colostate.edu/ramsdis ... display=12