Two African waves worth mentioning

By: Dr. Jeff Masters , 3:51 PM GMT on July 18, 2009

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There are two African tropical waves worth mentioning today, though neither looks particularly threatening. A tropical wave near 12N 45W, about 1200 miles east of the Lesser Antilles Islands (97 L), is moving west at 15 - 20 mph. This wave is now surrounded by an area of very dry air from the Sahara Desert. The dry air has disrupted most of the wave's heavy thunderstorm activity, and will continue to make it difficult for this system to develop over the next 2 - 3 days. Wind shear is a modest 10 knots over the disturbance, and should remain in the moderate 10 - 15 knot range over the next 2 - 3 days. Thereafter, shear is expected to rise to 20 - 30 knots. This morning's QuikSCAT pass showed no evidence of a surface circulation, and only a modest wind shift associated with 97L. The National Hurricane Center is giving this system a low (less than 30% chance) of developing into a tropical depression in the next 48 hours.

A second tropical wave now approaching the northern Lesser Antilles Islands is under 30 knots of wind shear, and has little prospect of development due to the high shear. However, the wave will bring heavy rain to the islands over the next two days.

None of the computer models are forecasting tropical storm development over the next seven days, and I don't expect either of the two African waves mentioned today to develop over at least the next three days.


Figure 1. Current satellite image of African wave 97L, 1200 miles east of the Lesser Antilles Islands.

I'll have an update Sunday afternoon.
Jeff Masters

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Quoting hunkerdown:
I don;t really think the ULL will have any impact on ex97 unless ex97 takes a NW to N of NW track.


Yeah thats really the only way it could have an impact. Yet a more NW track isnt out of the question.
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Quoting WeatherStudent:


Will that affect it positively or negatively? Cheers!
I don;t really think the ULL will have any impact on ex97 unless ex97 takes a NW to N of NW track.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting WeatherStudent:


Will that affect it positively or negatively? Cheers!


Remains to be seen. It all depends on how EX97L moves in the next 24-48 hours.
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Quoting hunkerdown:
Its all about the timing, as always with tropical systems.


Exactly. If it moves due W for the next few days then it my encounter the rapidly lowering shear of the S Caribbean. Although if it moves 15-20mph to the NW the it'll run into the rather hostile shear in the North Caribbean.
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Quoting weatherwatcher12:

I was saying wouldn't it move from the Caribbean and move to the Bahamas
No, it is really north of the islands to begin with (I don't consider north of the islands the Caribbean).
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Stormchaser2007:

It is moving out but it remains to be seen if its moving fast enough to allow for some favorable shear.
Its all about the timing, as always with tropical systems.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Stormchaser2007:


More WSW.


agree
Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting StSimonsIslandGAGuy:
What do you think the odds are of each yellow area being named?


The Antilles blob is dead. I give ex97L a <20% chance of being named.
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Quoting WeatherStudent:


SW?


More WSW.
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Quoting hunkerdown:
Its not really in the Caribbean, it is in the ATL JUST north of the Caribbean.

I was saying wouldn't it move from the Caribbean and move to the Bahamas
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Quoting WeatherStudent:


SW?
Looks a little more like WSW for now.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting weatherwatcher12:

From the Caribbean. Won't it stay in the Bahama's
Its not really in the Caribbean, it is in the ATL JUST north of the Caribbean.
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Quoting hunkerdown:
I believe the TUTT should be moving out.

It is moving out but it remains to be seen if its moving fast enough to allow for some favorable shear.
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Quoting hunkerdown:
I believe the TUTT should be moving out.

From the Caribbean. Won't it stay in the Bahama's
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1481. sky1989
Quoting WeatherStudent:


What direction is it moving in? Away or towards EX-97L?


It seems to be moving to the southwest; 97L is moving to the west. However, 97L seems to be moving more quickly than the upper level low, so the upper level low may cause detrimental, high wind shear in the future of 97L. I could be wrong, and things could change though.
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Quoting weatherwatcher12:

If it goes there the TUTT will rip it apart
I believe the TUTT should be moving out.
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Quoting WeatherStudent:


What direction is it moving in? Away or towards EX-97L?


The ULL is moving west
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Quoting WeatherStudent:


What direction is it moving in? Away or towards EX-97L?


Im pretty sure you can tell from the animation.
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Quoting stillwaiting:
97L looks to be a bahama boma sometime next weekend,IMO might even become Ana before arriving!!!

If it goes there the TUTT will rip it apart
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Very nice ULL to the north.

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97L looks to be a bahama boma sometime next weekend,IMO might even become Ana before arriving!!!
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850mb vort:

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1471. Relix
Damn, the Antilles blob exploded into nothingness XD!!
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Speaking of media coverage, has anyone ever heard of the Amani Channel? I know I never have. But other than the AP this is one of the only channels that actually did coverage of Bolivar after Ike.

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2am TWO should stay the same as the 8pm TWO. Cept for the Antilles blob.
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Quoting Drakoen:
It really needs to improve itself right now at the lower levels. all of this happening now is just an embellishment.


Only has a short window left IMO!
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Quoting Drakoen:
I'm going to bed. Night all.


Night.
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850mb vorticity has increased a bit and has become more organized for what its worth.
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1462. Drakoen
I'm going to bed. Night all.
Member Since: October 28, 2006 Posts: 57 Comments: 29864
drakoen do u see it improving at the lower levels?
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Quoting WeatherStudent:


So that's it for it then, Chaser?


Not necessarily...FNMOC tends to update faster than NRL.
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1459. Drakoen
It really needs to improve itself right now at the lower levels. all of this happening now is just an embellishment.
Member Since: October 28, 2006 Posts: 57 Comments: 29864
97L looking a little better I see.
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This navy site is still carrying it
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Quoting Orcasystems:
CMC T = 60 Southern Florida

mm5fsu-merge T = 24 GOM



Longer Range CMC
- Florida and Carols.
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Looks like it'll cross 50W before morning breaks.

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1453. Drakoen
Quoting stormsurge39:
Where is its center of circulation? Is it in the convection or behind it?


The center of the system coincides well with the cimss 850mb vorticity as well as the microwave imagery. I have the center around 12.5N 49W. It's easy to see on satellite.
Member Since: October 28, 2006 Posts: 57 Comments: 29864
Where is its center of circulation? Is it in the convection or behind it?
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CMC T = 60 Southern Florida

mm5fsu-merge T = 24 GOM

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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