African Tropical Wave 98L Moving Over Cooler Waters

By: Dr. Jeff Masters , 2:23 PM GMT on July 23, 2013

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A strong and well-organized tropical wave that moved off the coast of Africa on Monday (98L) is located a few hundred miles south of the Cape Verde Islands and is moving west-northwest at 15 - 20 mph. Satellite images show that 98L has a decent amount of spin, but only a modest amount of heavy thunderstorms that have not changed much in intensity or areal coverage this morning. The wave is under a moderate 10 - 20 knots of wind shear, which will tend to allow slow development. A large amount of dry air lies to the north and west of 98L, and this dry air will likely interfere with development later this week. The SHIPS model predicts that wind shear will stay in the moderate range through Saturday. Ocean temperatures are barely adequate for development, about 26.5°C today, and will be below average over the region of ocean 98L will be traversing on Wednesday and Thursday, 25 - 26°C. These temperatures are very marginal for development. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, does not favor increased chances of Atlantic tropical cyclone formation this week. The reliable computer models for tropical cyclone genesis do not predict that 98L will develop this week. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 98L a 40% chance of developing into a tropical cyclone by Thursday. 98L should maintain a west-northwest track through the week, and may spread heavy rains and gusty winds to the northern Lesser Antilles Islands beginning on Saturday night or on Sunday.


Figure 1. Satellite image of 98L off the coast of Africa taken at 8 am EDT Tuesday July 23, 2013, with a satellite analysis of where dry air is, as well. A large amount of dry air lies to the north and west of 98L, and will likely interfere with development later this week. Image credit: University of Wisconsin CIMSS and NOAA/HRD.

Jeff Masters

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Quoting 2468. CybrTeddy:


He's been named, up to 50mph per the ATCF.
It's not official. NHC is the one that makes it official!
Member Since: Posts: Comments:
Quoting 2466. washingtonian115:
One similarity is that they are very small storms.I'm still meh about Dorian's future.It's gonna have to prove it's self to me a lot.

True they are both small, aye. What is more concerning and some bloggers touched on it yesterday is if it avoids the carribean and has no land interaction heading to the Bahamas. We will have high sst; shear, ULL interaction and of course the strength and oreintation of the High will be key.
Member Since: July 7, 2005 Posts: 0 Comments: 5165
Quoting 2461. wunderkidcayman:

maybe and maybe Dorian could turn W now and continue W right into the caribbean

Wunderkid I hate to put you down but this isn't headed for the Caymans.Sorry just isn't in Dorian's future..
Member Since: August 14, 2010 Posts: 10 Comments: 16432
A Cat 2 by 19N 62W would be nice XD
Member Since: October 6, 2007 Posts: 0 Comments: 5968
Quoting 2464. FOREX:


Haven't heard any talk about the Gulf with this which is good.


I'm talking about the gulf coast

Recurve isn't looking overly likely at this point but it's so far out that you can't talk about it with any confidence
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2473. Grothar
Quoting 2461. wunderkidcayman:

maybe and maybe Dorian could turn W now and continue W right into the caribbean



Never happen.
Member Since: July 17, 2009 Posts: 69 Comments: 25388
Quoting 2449. Patrap:


Looks Lik Georges 98 dere me tinks.

Im gonna file dat un.
The track yes, but different times of the year, I know you know that. What to take from this is that by time this reaches say the longitude of PR. the trough would have likely lifted out by then or why else would it turn on a more westward heading.
Member Since: June 30, 2013 Posts: 11 Comments: 7530
2471. Grothar
Quoting 2437. weatherh98:



And uh

This one (should it hold together) may effect other United States areas because that high is gonna be pretty strong


The intensity models aren't very strong
Member Since: July 17, 2009 Posts: 69 Comments: 25388
2470. LargoFl

- - - MAXIMUM WIND SPEED (INTENSITY) PROBABILITIES - - -

VALID TIME 18Z WED 06Z THU 18Z THU 06Z FRI 06Z SAT 06Z SUN 06Z MON
FORECAST HOUR 12 24 36 48 72 96 120
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
DISSIPATED 1 3 5 8 9 9 12
TROP DEPRESSION 31 20 22 25 25 26 28
TROPICAL STORM 67 72 66 59 58 57 53
HURRICANE 1 5 6 9 9 8 7
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
HUR CAT 1 1 5 5 8 8 7 6
HUR CAT 2 X X 1 1 1 1 1
HUR CAT 3 X X X X X X X
HUR CAT 4 X X X X X X X
HUR CAT 5 X X X X X X X
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
FCST MAX WIND 35KT 40KT 40KT 40KT 40KT 40KT 40KT
Member Since: August 6, 2011 Posts: 4 Comments: 36972
2469. dabirds
Quoting 2421. washingtonian115:
Dorian is a he..not sure why some people are saying she...it looks like that wave over africa wants to become something to.
Probably One Life to Live fans - Dorian Lord - meanest b**** on show. Had girl roomates in college, don't know why rem that, but when saw the name earlier this year jolted memory. Can't say I've ever met a real life male or female Dorian though.

The NE flow has begun in S C IL, 67 w/55 dew pt, 2-13 NE winds, 29.93". Looks like 3 out of 4 weekends in July the A/C will be off. Don't think I've ever been able to do that before in 19 yrs been in house. June, maybe one or two Augusts, but never in July.
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Quoting 2433. Waltanater:
...and it's not even officially named yet!


He's been named, up to 50mph per the ATCF.
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Quoting 2444. washingtonian115:
Well let's say that GFS shear forecast was right...Then what do you all think the strength of Dorian would be?.It's open to all..


85 mph IF THE SHEAR IS AS FORECASTED BY GFS
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Quoting 2462. sporteguy03:

This is no where even comparable to Chantal anyways I don't see much similiarities really.
One similarity is that they are very small storms.
Quoting 2459. Hurricanes305:


I think cooler temps will stop this from RI over the next 36 hours so it should more than hold its own but after that like the LGEM is saying a Cat. 2 is possible bearing down on the Northern Antilles and Bahamas. Is anyone else antsy to see what the NHC has got to say at 11. So much has change in mere hours which I find alarming.
I'm still meh about Dorian's future.It's gonna have to prove it's self to me a lot.
Member Since: August 14, 2010 Posts: 10 Comments: 16432
Quoting 2451. scott39:
Anti-cyclone should re-establish itself, to help Dorian fight off wind shear.


Shear is looking good for a long time if the GFS is right. Which is very unsettling. Time to get some fruits and go into 24 hour watch once it enter Herbert box. This blog is going to explode.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
2464. FOREX
Quoting 2437. weatherh98:



And uh

This one (should it hold together) may effect other United States areas because that high is gonna be pretty strong


Haven't heard any talk about the Gulf with this which is good.
Member Since: Posts: Comments:
Quoting 2434. EyEtoEyE:
Sorry Chucktown , Dorian will be a hurricane , sooner than we might think ! I just don't see a big recurve, maybe a minor recurve , then back west .


Quoting 2425. Chucktown:


It ain't going anywhere. I'd be surprised if there even is a Dorian by the end of the weekend.


Patience to the both of you, we don't even know what Dorian is going to do today, much less the position of an ULL 5 days out. Could be in a position to either shear or ventilate Dorian.
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Quoting 2414. CybrTeddy:


Chantal died because of its fast forward speed. Never really had a chance.

This is no where even comparable to Chantal anyways I don't see much similiarities really.
Member Since: July 7, 2005 Posts: 0 Comments: 5165
Quoting 2439. Grothar:
The models are moving more WNW on each run. Well it looks like this may miss the Caribbean entirely.



maybe and maybe Dorian could turn W now and continue W right into the caribbean

Member Since: June 13, 2009 Posts: 2 Comments: 11138
From where this storm began and if it ends up in the GOM when it is all said and done and being that it is still July would be an impressive feat if it were to accomplish that. By the way using Aug. and Sept. analogs will be quite useless because the pattern is different in July than in those 2 months.
Member Since: June 30, 2013 Posts: 11 Comments: 7530
Quoting 2437. weatherh98:



And uh

This one (should it hold together) may effect other United States areas because that high is gonna be pretty strong


I think cooler temps will stop this from RI over the next 36 hours so it should more than hold its own but after that like the LGEM is saying a Cat. 2 is possible bearing down on the Northern Antilles and Bahamas. Is anyone else antsy to see what the NHC has got to say at 11. So much has change in mere hours which I find alarming.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
2458. StormWx
850mb vorticity not quite consolidated yet.

Every time i hear Dorian i think DeLorean and back to the future.
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2457. LargoFl
GFS at 150 hours..were is P.R.? and we dont know what size the storm will be...
Member Since: August 6, 2011 Posts: 4 Comments: 36972
Quoting 2407. Mclem1:

I know, Ive been waiting patiently for the images of Dexters sunrise stroll!


Post #2303 if you missed it. Some other pics from this morning in My Photos.
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Quoting 2417. LargoFl:
good..i have a friend in ponce..he's getting ready also..its a good thing people down there are informed


Yeah :)
Member Since: October 6, 2007 Posts: 0 Comments: 5968
2454. Patrap
98L has become 04L

The new URL is: http://www.ssd.noaa.gov/PS/TROP/floaters/04L/04L_f loater.html



You will be redirected there in 5 seconds
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Quoting 2443. GTstormChaserCaleb:


Hmmm shows it having little land interaction and intensifying..Florida?.Lolol.
Member Since: August 14, 2010 Posts: 10 Comments: 16432
2452. Grothar
Member Since: July 17, 2009 Posts: 69 Comments: 25388
2451. scott39
Anti-cyclone should re-establish itself, to help Dorian fight off wind shear.
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2450. Patrap
Atlantic - Caribbean Sea - Gulf of Mexico
Tropical Weather Outlook (en Español*)

800 AM EDT WED JUL 24 2013 Tropical Weather Discussion

805 AM EDT WED JUL 24 2013

Tropical Depression FOUR RSS Feed icon Satellite | Buoys | NDFD | Storm Archive

...TROPICAL DEPRESSION FORMS OVER THE EASTERN ATLANTIC...
5:00 AM EDT Wed Jul 24
Location: 13.9°N 28.1°W
Moving: WNW at 20 mph
Min pressure: 1008 mb
Max sustained: 35 mph
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2449. Patrap
Quoting 2443. GTstormChaserCaleb:




Looks Lik Georges 98 dere me tinks.

Im gonna file dat un.
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2448. LargoFl
Quoting 2445. nocanesplease:
Mets in PR expect this system to be between 150-300 miles away. Do you agree?
well if we believe the GFS model..NO....
Member Since: August 6, 2011 Posts: 4 Comments: 36972
2447. Skyepony (Mod)
Quoting 2433. Waltanater:
...and it's not even officially named yet!

NAVY has declared Dorian but NHC hasn't yet..
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Quoting 2422. CybrTeddy:
Here's the shear forecast at about 114 hours out, rather light at about 5-10kts. This can and will change before we get too excited.



Hmmm.. The shear is already low over our system it has become more anticyclonic. With the LGEM now saying Cat. 2 the chances of a Hurricane has gone up exponential since designation 5am. In a matter of 5 hours the whole game has changed intensity-wise only cool waters should slow strengthen from there things start getting interesting. I have to say I never saw this coming.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Quoting 2435. LargoFl:
Mets in PR expect this system to be between 150-300 miles away. Do you agree?
Member Since: Posts: Comments:
Well let's say that GFS shear forecast was right...Then what do you all think the strength of Dorian would be?.It's open to all..
Member Since: August 14, 2010 Posts: 10 Comments: 16432


Member Since: June 30, 2013 Posts: 11 Comments: 7530
Quoting 2430. Grothar:
The Doc should be on soon.






Round of applause for the CLP5 model

Right on line

*sarcasm*
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2441. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 36972
Quoting 2429. floridaboy14:
i wonder what we get come august and how strong they will be?
bad late august
Member Since: March 12, 2013 Posts: 8 Comments: 13646
2439. Grothar
The models are moving more WNW on each run. Well it looks like this may miss the Caribbean entirely.


Member Since: July 17, 2009 Posts: 69 Comments: 25388
All I can say is HELLO CAPE VERDE SEASON !
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Quoting 2424. Grothar:
Looks like the Bahamas and Florida will eventually be in the Cone of Concern soon.



And uh

This one (should it hold together) may effect other United States areas because that high is gonna be pretty strong
Member Since: Posts: Comments:
2436. Patrap
Member Since: Posts: Comments:
2435. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 36972
Sorry Chucktown , Dorian will be a hurricane , sooner than we might think ! I just don't see a big recurve, maybe a minor recurve , then back west .
Member Since: Posts: Comments:
Quoting 2421. washingtonian115:
Dorian is a he..not sure why some people are saying she...it looks like that wave over africa wants to become something to.
...and it's not even officially named yet!
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The Bermuda high is showing signs of strenghening. don't be surprise in the next 24 hrs soon to be Dorian resumes a westerly course.
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2431. LargoFl
Quoting 2424. Grothar:
Looks like the Bahamas and Florida will eventually be in the Cone of Concern soon.
..I think your right Gro..south floridians should be reviewing their storm kits etc..by monday we should know for sure..
Member Since: August 6, 2011 Posts: 4 Comments: 36972
2430. Grothar
The Doc should be on soon.


Member Since: July 17, 2009 Posts: 69 Comments: 25388
i wonder what we get come august and how strong they will be?
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Quoting 2422. CybrTeddy:
Here's the shear forecast at about 114 hours out, rather light at about 5-10kts. This can and will change before we get too excited.

Member Since: August 14, 2010 Posts: 10 Comments: 16432

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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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