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 BurnedAfterPosting:
ok time for a game

which is the most likely scenerio for the 8pm TWO

A) Both yellow circles go away
B) One yellow circle goes away, one remains
C) Both yellow circles remain
D) One of the yellow circles becomes and orange circle.

Vote now!!


C
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Quoting hunkerdown:
Especially if you are on this blog, no blogging and driving...get a designated driver.
you mean a designated blogger..
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Shear lowers when the system begins to move up the coast. When and if the system enters the Bahamas, shear will be unfavorable because of an upper level trough.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Quoting BurnedAfterPosting:
ok time for a game

which is the most likely scenerio for the 8pm TWO

A) Both yellow circles go away
B) One yellow circle goes away, one remains
C) Both yellow circles remain
D) One of the yellow circles becomes and orange circle.

Vote now!!
B
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Funkadelic:
WOW crazy rain here in Boca Raton FL..... very gusty winds and the rain is coming down so fast I cant see the house in front of me.. Stay off the roads in south east florida tonight!
Especially if you are on this blog, no blogging and driving...get a designated driver.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
ok time for a game

which is the most likely scenerio for the 8pm TWO

A) Both yellow circles go away
B) One yellow circle goes away, one remains
C) Both yellow circles remain
D) One of the yellow circles becomes and orange circle.

Vote now!!
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Wow! Strong winds and heavy rains expected from the wave :
WindGuru 18Z GFS for St Martin (Northern Leeward Islands)

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Quoting HurricaneSwirl:


i knew what you meant, i dont take offense much anyways. btw im a man. XD
Ok.
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WxLogic 6:05 PM CDT on July 18, 2009

I kinda agree with yas there,too many folks run with the IR Look and never visit the visible,and well,thats where the business ends usually starts.

I trust my eyes as well as my reading.
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Quoting tropicfreak:


Don't poof it yet, conditions ahead of it are ripe for development. Shear is low in the carribean, waters are warm and the air is moist. i can't belive you're writing of x-97L when it hasn't developed yet. Give it some time folks, it'll develop.

you are right I have seen invest that go down hill and you can only see a bit of it left on the vis then blow up and become a hurricane
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Quoting stormwatcherCI:
Sorry about that but I don't know if you are male or female so I put both.


i knew what you meant, i dont take offense much anyways. btw im a man. XD
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Quoting Patrap:
Floater 1 - Visible Loop

Running the Loop FAST shows the energy west of the Leewards pulling WEST.

The Convection over the Islands is waning and isnt the Player.



Indeed... if it wasn't for the strong shear... this bad boy (hehe... or girl in this case) would have been a TD and not surprised by the winds I was seen on some of the island a TS by later tonight.
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Quoting Patrap:
Floater 1 - Visible Loop

Running the Loop FAST shows the energy west of the Leewards pulling WEST.

The Convection over the Islands is waning and isnt the Player.

Therefore, it is the convection flaring in the Caribbean ?
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Quoting HurricaneSwirl:


thanks lol :)
just dont put man and woman so close together next time because i almost took it as you calling me a big manwoman LOL
Sorry about that but I don't know if you are male or female so I put both.
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Quoting HurricaneSwirl:


thanks lol :)
just dont put man and woman so close together next time because i almost took it as you calling me a big manwoman LOL

lol
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Floater 1 - Visible Loop

Running the Loop FAST shows the energy west of the Leewards pulling WEST.

The Convection over the Islands is waning and isnt the Player.

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Quoting tropicfreak:


Don't poof it yet, conditions ahead of it are ripe for development. Shear is low in the carribean, waters are warm and the air is moist. i can't belive you're writing of x-97L when it hasn't developed yet. Give it some time folks, it'll develop.


97L is officially gone, no more, ceases to exist anymore
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Quoting StSimonsIslandGAGuy:
The refresh problem seems to have been solved, at least for now :) Not had any trouble after dinner.
Maybie it was your dinner ???
Member Since: August 15, 2008 Posts: 0 Comments: 2515
Quoting Patrap:
If your running FireFox 3 and having Wu-issues,

..restart your system as FF3 has a new fix


Hehe... adding to that... make sure you're on 3.5.1... seems to be doing pretty good for me.
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Quoting Weather456:


Very true, near the Bahamas but look at post 788, that tropical storm offshore NC is the GFS at 132 hrs or Friday. :)
But it would have to get through the heavy shear in the Bahamas first early to mid week, so it would be quite puzzling how it would be so developed after that just a day or two later...ahhh the fun of computer models, what is their thinking or reasoning.
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Quoting stormwatcherCI:
You are a big man(woman). Nice when someone is decent enough to apologize when they are wrong. Don't see it happening too much on here.


thanks lol :)
just dont put man and woman so close together next time because i almost took it as you calling me a big manwoman LOL
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Quoting Drakoen:


The vort max isn't heading north like the models are suggest at the present time. Will be interesting. The CMC proposed a more southern track for the maximum.


Indeed... that's why I'm favoring a more southern solution like CMC and UKMET are somewhat forecasting... but it will definitely be interesting to see how thing will unfold by early next week.
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Quoting Tazmanian:
i called it good last night


97L is in fac RIP Poof gone


Don't poof it yet, conditions ahead of it are ripe for development. Shear is low in the carribean, waters are warm and the air is moist. i can't belive you're writing of x-97L when it hasn't developed yet. Give it some time folks, it'll develop.
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Quoting reedzone:


Actually the map he posted has been updating every hour. convection is coming back and regeneration is possible as it now enters in a better environment.


agree, should be interesting to see how it acts during Dmax. Less dry air as it heads into the Caribbean.
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If your running FireFox 3 and having Wu-issues,

..restart your system as FF3 has a new fix
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Quoting leftovers:
run the last visiable of the windwards area or loop it seems as if a anti cyclone is building. not sure if this trend continues notice the clouds are fanning out.


There is an existing upper level high mentioned in the 2 PM Tropical Weather Discussion

SCATTERED SHOWERS AND TSTMS ARE CONCENTRATED MAINLY E OF 64W AND ARE BEING ENHANCED BY AN UPPER LEVEL DIFFLUENT PATTERN DUE TO AN UPPER HIGH CENTERED NEAR 14N66W.
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Quoting hunkerdown:
Except that map is for the 24th (next Friday), the wave is "supposed" to be in the Bahamas around the 21st (Tuesday).


Very true, near the Bahamas at 72 hrs but look at post 788, that tropical storm offshore NC is the GFS at 132 hrs or Friday. :)
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Quoting WxLogic:
Latest 21Z Vorticity maps shows the low level VORT MAX moving S/SE of PR away from the convection to the E of the Windward Islands... RGB Sat imagery shows this feature quite nicely heading away (West) from the convection... which has been causing gusty conditions in the coastal areas of PR earlier today.

I will not be surprised that NHC drops the probability circle by tomorrow AM if a new vorticity area closer to the convection doesn't develop or if the current low level vorticity doesn't start generating convection of its own.

I guess we'll see how things play out during DMAX tomorrow AM and NHC. :)


The vort max isn't heading north like the models are suggest at the present time. Will be interesting. The CMC proposed a more southern track for the maximum.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Quoting hunkerdown:
Except that map is for the 24th (next Friday), the wave is "supposed" to be in the Bahamas around the 21st (Tuesday).


yup you are right, shear will not be favorable in the bahamas at the time the wave at 60W is expected to be there
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Quoting MasterOfStorms:
When I refresh this page,it takes my like 5 times to get back to this blog.


Sure sign the season is here...Blogholes are back...I usually just re-navigate to the blog using the wunderblogs link at top.
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The wave in the islands is fanning out, I think because of shear.
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Quoting StormJunkie:
Good to have you back 456, and afternoon to you.



Thanks and a good afternoon (evening) to you too.
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Quoting HurricaneSwirl:


ah, nope, you were correct as W456 pointed out apparently. LOL i should have checked myself so i apologize.
Except that map is for the 24th (next Friday), the wave is "supposed" to be in the Bahamas around the 21st (Tuesday).
Member Since: August 15, 2008 Posts: 0 Comments: 2515
97l is in low shear.5 to 10 kt max.I don"t see why it can't form.
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Severe T-Storm warning for Eastern Palm Beach County.
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Quoting Chucktown:
Ex 97 is getting torn apart - a sure sign of high shear is that the forward motion looks like it has hit a wall. The low level circulation continues to push WNW (can't see it anymore without the visible) while at the same time the cloud tops are continually getting pushed east from the shear.


actually it isnt shear that is doing that, it is the movement of the system, it is moving too fast, so it makes it look like shear
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Quoting AllStar17:


456, how strong could that possibly get if it materialized?


If it does, most likely a TS.
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Quoting HurricaneSwirl:


ah, nope, you were correct as W456 pointed out apparently. LOL i should have checked myself so i apologize.
You are a big man(woman). Nice when someone is decent enough to apologize when they are wrong. Don't see it happening too much on here.
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Good to have you back 456, and afternoon to you.
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Quoting AllStar17:


Looks like it is going due west.


I think I see it..but wouldn't it be heading into a mountain of shear?
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Latest 21Z Vorticity maps shows the low level VORT MAX moving S/SE of PR away from the convection to the E of the Windward Islands... RGB Sat imagery shows this feature quite nicely heading away (West) from the convection... which has been causing gusty conditions in the coastal areas of PR earlier today.

I will not be surprised that NHC drops the probability circle by tomorrow AM if a new vorticity area closer to the convection doesn't develop or if the current low level vorticity doesn't start generating convection of its own.

I guess we'll see how things play out during DMAX tomorrow AM and NHC. :)
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Quoting Patrap:
It Moving west at 23mph


Now, how is it going to get in the Bahamas if it is going west is my question.
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i called it good last night


97L is in fac RIP Poof gone
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Ex 97 is getting torn apart - a sure sign of high shear is that the forward motion looks like it has hit a wall. The low level circulation continues to push WNW (can't see it anymore without the visible) while at the same time the cloud tops are continually getting pushed east from the shear.
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Quoting Patrap:
Floater 1- Visible Loop

By running the Caribbean Loop above on Fast,one can see the Circulation west of the Leeward in the Caribbean.
Albeit a poor one.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
When I refresh this page,it takes my like 5 times to get back to this blog.
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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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