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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Shear or no shear affecting Ex 97L. You be the judge.

Speed up the loop...
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Tampa spin, NHC used the "words at this time" on referring to the shear being too stong.It is forcasted to change.
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Quoting btwntx08:
ex 97 is blowing up quite nicely
Come on, you should know better, its from all that shear. Must be 50-100 knots out there, and right ove the dang thing. Don't you see the clouds streaming off ?
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting WeatherStudent:



Chill out, TS! What is up with you lately? Why have you've become so rude to many of us on here recently? Are you going through something personal or what? A quick, yet final FYI: Say it, don't spray it next time, geeze. Cheers, :)


I'm sorry if im coming across Rude! But, i'm sorry you can't see the strong Shear starting to hit 97L....That's not being rude! Just trying to make my point what you see vs. what i see.......Point of fact! Your saying you disagree with NHC also. OK!
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Quoting TampaSpin:


LOOK AT THE LOOP YOU POSTED! LOOK AT THE STREAM OF CLOUDS POINTING FROM THE NW over ex 97L...YOU DON'T SEE THEM POINTING and moving South WEst toward 97L! I give up! I said the other night that strong shear would start hitting 97L late Saturday/Sunday! I don't know what else i can do to say. NHC just comfirmed the same! SORRY we choose to disagree. But, this is just what i See as well as the folks at NHC!


The clouds moving NW are not 'over' ex97L. Anyway im pretty much done discussing this because were both just to deep into our opinions and it looks like neither one of us will budge. We'll see whos right by tomorrow night. And for the record I do not see Ex97L developing in the near or long term.
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TS, no need to type in CAPS. People disagree. Not everyone will view things the same you do.
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Quoting Stormchaser2007:


Look at the facts...

Better yet look at the dang map I JUST posted.


LOOK AT THE LOOP YOU POSTED! LOOK AT THE STREAM OF CLOUDS POINTING FROM THE NW over ex 97L...YOU DON'T SEE THEM POINTING and moving South EAST toward 97L! I give up! I said the other night that strong shear would start hitting 97L late Saturday/Sunday! I don't know what else i can do to say. NHC just comfirmed the same! SORRY we choose to disagree. But, this is just what i See as well as the folks at NHC!
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Very moist out there
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Lol...TS is not posting. Facts catch up with you eventually no matter how hard you try and resist. Im waiting for the 6UTC CIMSS maps then im gone.
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Quoting Stormchaser2007:


The GIF was already a loop thus it was postable.

oh
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The convection is developing right where the max vorticity is:
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Quoting weatherwatcher12:

How do you post a loop?


The GIF was already a loop thus it was postable.
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Quoting Stormchaser2007:


Please enlighten me to where the heck your unfavorable shear is?

Ex97L is at 12N 50 W. Looks like its on the edge of the decreasing shear.

SHEAR

How do you post a loop?
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Quoting TampaSpin:


LOL! So sorry you don't see what i was trying to tell you all! NHC see's the Shear!
From the CURRENT shear map, shear over ex97 is 5-10 but just in front of it is 30-40. BUT, according to the tendency map, the area of 30-40 should be decreasing by 20.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Stormchaser2007:


Please enlighten me to where the heck your unfavorable shear is?

Ex97L is at 12N 50 W.

SHEAR

The worst shear affecting it is a modest 10 knots
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Quoting TampaSpin:


So your disagreeing with NHC and me! That, hard shear is starting to hit EX. 97L...WOW! Keep trying to prove your point! Maybe someone blind will listen!


Look at the facts...

Better yet look at the dang map I JUST posted.
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Good night y'all. Thanks for the help guys.:)
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Quoting Stormchaser2007:


Please enlighten me to where the heck your unfavorable shear is?

Ex97L is at 12N 50 W.



lmao. Well to each his own when reading shear maps I guess. I see nothing on that which indicates any unfavorable upper level winds where the system is.
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Quoting StSimonsIslandGAGuy:
I think it may be more the dry air hurting the old 97L than the shear. But anyway, night y'all!

The dry air seems to be backing off a bit.
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Quoting WeatherStudent:
I'm I being ignored on here this morning?


Awww WS, what makes you say that? LOL (sound familiar???) lol! :):)
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Quoting Stormchaser2007:


Bit of a freak out...

Regardless of all the maps I post that shows 10knots of shear you still try to make us believe that there is highly unfavorable shear over this...no getting through to you. The harder we try to show you the way things are the more you pull back and believe the opposite. Regardless im off to bed.


So your disagreeing with NHC and me! That, hard shear is starting to hit EX. 97L...WOW! Keep trying to prove your point! Maybe someone blind will listen!
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Quoting TampaSpin:


LOL! So sorry you don't see what i was trying to tell you all! NHC see's the Shear!


Please enlighten me to where the heck your unfavorable shear is?

Ex97L is at 12N 50 W. Looks like its on the edge of the decreasing shear.

SHEAR
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Quoting TampaSpin:


NO IT'S NOT! THIS IS WHAT I HAVE BEEN SAYING! NHC JUST COMFIRMED WHAT I WAS SAYING! SHEAR IS STARTING TO HIT IT HARD! OH WELL!


Bit of a freak out...

Regardless of all the maps I post that shows 10knots of shear you still try to make us believe that there is highly unfavorable shear over this...no getting through to you. The harder we try to show you the way things are the more you pull back and believe the opposite. Regardless im off to bed.
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Quoting StSimonsIslandGAGuy:
I wonder if they will drop one of the yellow areas at the 2 am TWO.
See 1508.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Stormchaser2007:
Upper level winds are about 5-10 knots. Not really unfavorable.


LOL! So sorry you don't see what i was trying to tell you all! NHC see's the Shear!
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Quoting weatherwatcher12:

A hard 10 knots of shear?
Don't bother.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting TampaSpin:


NO IT'S NOT! THIS IS WHAT I HAVE BEEN SAYING! NHC JUST COMFIRMED WHAT I WAS SAYING! SHEAR IS STARTING TO HIT IT HARD! OH WELL!

A hard 10 knots of shear?
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The convection is starting to consolidate around the core.

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Quoting WeatherStudent:


Indeed, ackward.


NO IT'S NOT! THIS IS WHAT I HAVE BEEN SAYING! NHC JUST COMFIRMED WHAT I WAS SAYING! SHEAR IS STARTING TO HIT IT HARD! OH WELL!
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AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 46W/47W TO THE SOUTH
OF 16N MOVING WEST 15 TO 20 KT. BROAD CYCLONIC FLOW COVERS THE
ATLANTIC OCEAN FROM 7N TO 14N BETWEEN 45W AND 54W. SCATTERED
MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE FROM 10N
TO 14N BETWEEN 47W AND 51W. POSSIBLE SHOWERS ARE ELSEWHERE
FROM 10N TO 13N BETWEEN 40W AND 50W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 63W/64W TO THE SOUTH OF
22N MOVING WESTWARD 15 TO 20 KT. THE WAVE IS MOVING AWAY FROM
THE UPPER LEVEL TROUGH THAT WAS RIGHT ON TOP OF IT 24 HOURS AGO.
THE WAVE NOW IS MOVING THROUGH AN AREA OF UPPER LEVEL
ANTICYCLONIC WIND FLOW THAT COVERS THE CARIBBEAN SEA TO THE
SOUTH OF 20N TO THE EAST OF A LINE FROM SOUTHEASTERN CUBA TO
THE NORTH CENTRAL HONDURAS COAST.

from the discussion
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Member Since: August 17, 2005 Posts: 26 Comments: 16436
Still two yellows at the TWO. I have no idea what they are seeing in the 60W ex-blob to keep the yellow.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting hunkerdown:
The models will dance all around when dealing with a "system" like ex97. To predict tracts, models will have a very tough time with systems that have no formation to them (almost guesswork for the model). They are only as good as their initialization. You know the ole saying, garbage in, garbage out...


Ah. I see.Thanks. Thought it was a little strange. :)
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Upper level winds are about 5-10 knots. Not really unfavorable.
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Quoting weatherwatcher12:
000
ABNT20 KNHC 190533
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN JUL 19 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE EASTERN CARIBBEAN SEA IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS AS IT MOVES WEST-
NORTHWESTWARD AT ABOUT 15 MPH. WHILE RAINFALL ASSOCIATED WITH THE
WAVE MAY BE LOCALLY HEAVY AT TIMES...UPPER-LEVEL WINDS REMAIN
UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM. THERE IS A
LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
900 MILES EAST OF THE WINDWARD ISLANDS HAS INCREASED A LITTLE THIS
EVENING. HOWEVER...UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT AT THIS TIME. THERE IS A LOW CHANCE...LESS
THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN



Strange update. The shear over it is only 10 knots
Member Since: Posts: Comments:
000
ABNT20 KNHC 190533
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN JUL 19 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE OVER THE EASTERN CARIBBEAN SEA IS PRODUCING
DISORGANIZED SHOWERS AND THUNDERSTORMS AS IT MOVES WEST-
NORTHWESTWARD AT ABOUT 15 MPH. WHILE RAINFALL ASSOCIATED WITH THE
WAVE MAY BE LOCALLY HEAVY AT TIMES...UPPER-LEVEL WINDS REMAIN
UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM. THERE IS A
LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
900 MILES EAST OF THE WINDWARD ISLANDS HAS INCREASED A LITTLE THIS
EVENING. HOWEVER...UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT AT THIS TIME. THERE IS A LOW CHANCE...LESS
THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN


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Quoting homelesswanderer:


I was wondering about that. It seems at least 3 models are very diverse on the track. GFS from what I can tell takes it up east of Florida in the Atlantic. I think? And as Orca pointed out, Fla Carolina or sw gom. This should be interesting if it holds together.
The models will dance all around when dealing with a "system" like ex97. To predict tracts, models will have a very tough time with systems that have no formation to them (almost guesswork for the model). They are only as good as their initialization. You know the ole saying, garbage in, garbage out...
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Stormchaser2007:


Remains to be seen. It all depends on how EX97L moves in the new 24-48 hours.


I was wondering about that. It seems at least 3 models are very diverse on the track. GFS from what I can tell takes it up east of Florida in the Atlantic. I think? And as Orca pointed out, Fla Carolina or sw gom. This should be interesting if it holds together.
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.