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

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SconnieCane
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Re: Area Between Africa and Lesser Antilles 10/20

#21 Postby SconnieCane » Fri Aug 10, 2018 2:36 pm

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.

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Re: Area Between Africa and Lesser Antilles 10/20

#22 Postby lrak » Fri Aug 10, 2018 2:55 pm

Welcome SconnieCane I love this board. I've learned so much about the weather from these brainiacs :flag:
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Re: Area Between Africa and Lesser Antilles 10/20

#23 Postby gatorcane » Fri Aug 10, 2018 6:41 pm

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.

Image
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Re: Area Between Africa and Lesser Antilles 10/20

#24 Postby gatorcane » Fri Aug 10, 2018 6:49 pm

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Re: Area Between Africa and Lesser Antilles 10/20

#25 Postby AutoPenalti » Fri Aug 10, 2018 7:10 pm

gatorcane wrote: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.
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Re: Area Between Africa and Lesser Antilles 10/20

#26 Postby AnnularCane » Fri Aug 10, 2018 7:33 pm

I wonder if they think any unfavorable wind conditions will improve?
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Re: Area Between Africa and Lesser Antilles 10/20

#27 Postby gatorcane » Fri Aug 10, 2018 7:36 pm

AnnularCane wrote: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:

Image
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Re: Area Between Africa and Lesser Antilles 10/20

#28 Postby NotSparta » Fri Aug 10, 2018 7:43 pm

gatorcane wrote:
AnnularCane wrote: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


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Re: Area Between Africa and Lesser Antilles 10/20

#29 Postby Nimbus » Fri Aug 10, 2018 8:16 pm

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.
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Re: Area Between Africa and Lesser Antilles 10/10

#30 Postby cycloneye » Sat Aug 11, 2018 6:55 am

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.
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Re: Area Between Africa and Lesser Antilles 10/10

#31 Postby cycloneye » Sat Aug 11, 2018 12:53 pm

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.
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Re: Area Between Africa and Lesser Antilles 10/10

#32 Postby AutoPenalti » Sat Aug 11, 2018 1:44 pm

Interesting that now it’s scaled down to 10% in the next 5 days but does not mention unfavorable conditions.
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Re: Area Between Africa and Lesser Antilles 10/10

#33 Postby Hurricaneman » Sat Aug 11, 2018 2:16 pm

AutoPenalti wrote: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
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Re: Area Between Africa and Lesser Antilles 10/10

#34 Postby SootyTern » Sat Aug 11, 2018 2:27 pm

or maybe because it is stationary and won't be moving into better conditions anytime soon
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Re: Area Between Africa and Lesser Antilles 10/10

#35 Postby AnnularCane » Sat Aug 11, 2018 2:40 pm

Is it normal for an MDR disturbance to just go stationary like that?
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Re: Area Between Africa and Lesser Antilles 10/10

#36 Postby gatorcane » Sat Aug 11, 2018 5:57 pm

The GFS is developing this on the EPAC side in the long-range.
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Re: Area Between Africa and Lesser Antilles 10/10

#37 Postby cycloneye » Sat Aug 11, 2018 6:47 pm

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.
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Re: Area Between Africa and Lesser Antilles 10/10

#38 Postby AJC3 » Sat Aug 11, 2018 6:51 pm

AnnularCane wrote: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
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Re: Area Between Africa and Lesser Antilles

#39 Postby stormzilla » Mon Aug 13, 2018 10:17 am

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
Last edited by AJC3 on Mon Aug 13, 2018 9:15 pm, edited 3 times in total.
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Re: Tropical Wave ESE of Lesser Antilles

#40 Postby gatorcane » Wed Aug 15, 2018 10:13 am

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

Image

Image

Image
Last edited by gatorcane on Wed Aug 15, 2018 10:30 am, edited 2 times in total.
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