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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Welcome aboard NOLA Homie,..Uptown Ruler here.
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Hello all! I have been following WU blog for about 2 years now but had never posted. I do not have any "formal education" in weather, but I love it and monitor it daily. I enjoy all of your insights and also look forward to discussing the tropics. Weather has always fascinated me and I hope to learn new things through this blog.

Thanks in advance,

KC2NOLA
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Quoting BurnedAfterPosting:
97L is far from dead, dry air is being filtered out, these things take time

wave at 60W is clearly enhanced by the TUTT and is not self sustaining; you dont get developing systems in that scenerio

Guess we will see what happens


Hanna last year when she first tried to form was like this. The TUTT moved away and she finished developing then it got her again and she almost died. TUTTs can start a storm if they interact with a wave to get the convection going then they move apart.
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Quoting BurnedAfterPosting:
97L is far from dead, dry air is being filtered out, these things take time

wave at 60W is clearly enhanced by the TUTT and is not self sustaining; you dont get developing systems in that scenerio

Guess we will see what happens


Doesnt look that way...Looks like its eating some SAL. When its that close to the super dry air of the SAL then it will be impossible for it to maintain convection, thus not likely to develop. Although if that TUTT enhanced wave near the islands can fan out and spread out some moisture then things will be better for it and we'll see what happens.

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395. CUBWF
Is already on. I thought it will take at least 24 hrs.
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394. IKE
Quoting CUBWF:
How long take my handle to be approved after downloaded.


?

I see your handle...CUBWF.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
I know how SLU stated they are not going to combine but with this satellite i just cant say they wont, thoughts?
Link
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392. CUBWF
How long take my handle to be approved after downloaded.
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391. IKE
Quoting IKE:
12Z ECMWF takes the western wave up the east coast and strengthens it...


Also shows a weak secondary low heading into the GOM...real weak though. Stronger low heads up toward New England.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
97L is far from dead, dry air is being filtered out, these things take time

wave at 60W is clearly enhanced by the TUTT and is not self sustaining; you dont get developing systems in that scenerio

Guess we will see what happens

Tropical Floater Imagery
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Quoting Ossqss:
Patrap and other FireFox users, here is the info on the critical issue found the other day in 3.5

3.5.1 was released yesterday.

Just incase you need it :)

Link



Thank You
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I reconfigured and restarted my FF browser,.

Good to go now.
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Lowest pressure i found around the blob was 29.98 inches (1015.2 millibars) located around st. Johns.
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385. IKE
12Z ECMWF takes the western wave up the east coast and strengthens it...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Patrap and other FireFox users, here is the info on the critical issue found the other day in 3.5

3.5.1 was released yesterday.

Just incase you need it :)

Link
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Just my two cents from looking at the past 24hrs (models, shear, imagery, etc)...97l is done, just could not handle the dry air...And the 60w wave may actually be the one that needs to be watched. So far it is surviving, and even thriving to some extent, in the sheared environment...Just have to see how long it can go toe to toe with the shear.
Member Since: August 17, 2005 Posts: 26 Comments: 16504
SLU...your right about that. The shear is what is pushing the higher cloud tops off to the East/ North-East. If you view the visible satellite loop that will become more obvious.

Systems don't usually "merge" per say. The stronger system with the more well defined vorticy will usually absorb the weaker ones moisture and cause distruption to its formation. Unless its the fujiwhara effect which occurs in nearby strong vorticies.
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380. SLU
Quoting IKE:


Yeah....it's moving. You can see a swirl to the clouds in the NE Caribbean sea now.


Thank you sir!
Member Since: July 13, 2006 Posts: 12 Comments: 5109
Quoting SLU:


Which is so not true. The minimal central pressure of a system is relative to the background pressure of the environment. The strength of a system depends on the pressure gradient it can produce. If the background pressure is 1018mb, a system can have a minimum pressure of 1012mb and still produce tropical storm force winds because of the pressure gradient. So the wave in the Caribbean can have a low of 1014mb since the background pressure is very high in the area.

Secondly, westerly winds have been occurring in St. Lucia and southerly winds in Barbados. The convection on the eastern side is moving from south to north which is evidence of a low trying to form.

Finally, the two systems will not merge. The westerly upper level winds are blowing the high level clouds eastwards giving you the impression that the system is not moving much. it is move WNW at 15 - 20mph.


Thanks SLU. That is good info.
97L is barely discernable to me on floater. Looks better on Central Atlantic Infrared. bbl
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12Z CMC high resolution

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Ack, the blog is getting worse. My F5 is getting worn out!
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the blob is definitely fading and getting bigger...
Link
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375. IKE
Quoting SLU:


Which is so not true. The minimal central pressure of a system is relative to the background pressure of the environment. The strength of a system depends on the pressure gradient it can produce. If the background pressure is 1018mb, a system can have a minimum pressure of 1012mb and still produce tropical storm force winds because of the pressure gradient. So the wave in the Caribbean can have a low of 1014mb since the background pressure is very high in the area.

Secondly, westerly winds have been occurring in St. Lucia and southerly winds in Barbados. The convection on the eastern side is moving from south to north which is evidence of a low trying to form.

Finally, the two systems will not merge. The westerly upper level winds are blowing the high level clouds eastwards giving you the impression that the system is not moving much. it is move WNW at 15 - 20mph.



Yeah....it's moving. You can see a swirl to the clouds in the NE Caribbean sea now.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
according to the pressure out invest is slowly weakening and since it has 2-3 days of dry air followed by shear once the dryness lets up I think it's fair to say 97L is good as dead
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wu server is acting up,..

I cant stay Logged in.Have to keep re-Logging in to post.
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372. IKE
Interesting comments from the latest TWD....

"WATER VAPOR IMAGERY INDICATES THE WAVE IS BEGINNING TO
MOVE BENEATH AN UPPER LEVEL RIDGE ACROSS THE ERN CARIBBEAN
AND
THE NRN PORTION OF THE WAVE IS COMING UNDER THE IMPACTS OF AN
UPPER LOW CENTERED NE OF PUERTO RICO NEAR 23N58W."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
371. CUBWF
Already work, thank you.
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Pat...Earlier this afternoon, your posts were hidden on my p.c. Has to adjust the filter again. Also had to F5 a few times to get see the new postings.
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369. SLU
Quoting amd:
there is no surface low forming near Guadeloupe. After checking the latest surface observations both to the north and south of Guadeloupe, there is no evidence of a west, or north wind.

Also, pressure is still around 1016 mb at all locations that I checked, and the pressure needs to be around 1010 mb to suggest that a low may be forming.

One interesting thing to note is that 97L is still moving around 20 mph to the west, while the blob just east of the islands continues to be stationary. If the two interact, a tropical system can develop.


Which is so not true. The minimal central pressure of a system is relative to the background pressure of the environment. The strength of a system depends on the pressure gradient it can produce. If the background pressure is 1018mb, a system can have a minimum pressure of 1012mb and still produce tropical storm force winds because of the pressure gradient. So the wave in the Caribbean can have a low of 1014mb since the background pressure is very high in the area.

Secondly, westerly winds have been occurring in St. Lucia and southerly winds in Barbados. The convection on the eastern side is moving from south to north which is evidence of a low trying to form.

Finally, the two systems will not merge. The westerly upper level winds are blowing the high level clouds eastwards giving you the impression that the system is not moving much. it is move WNW at 15 - 20mph.

Member Since: July 13, 2006 Posts: 12 Comments: 5109
Patrap's posts are hidden, you have to click on "Show" to see them.
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Sorry to interrupt, But, I've been reading these posts and it's starting to confuse me because some of y'all say yes and the others say no on a lot of things here. I was on here last year and I learned a lot. But not enough to comment either way. I like to watch weather and I like to learn it as well. Y'all are confusing the heck out of me this year LOL.
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361. CUBWF 2:40 PM EDT on July 18, 2009
Why I can't see Patrap an others posts. Are they banned or something?

Change your filter settings. (That is located just above where the posts start.)
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right now 97L is moving at W (275 degrees) at 23 mph.
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I dont feel Banned..?


A lil tardy maybe,but not banned.

Some server issues for some areas with wu today.
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Quoting amd:
there is no surface low forming near Guadeloupe. After checking the latest surface observations both to the north and south of Guadeloupe, there is no evidence of a west, or north wind.

Also, pressure is still around 1016 mb at all locations that I checked, and the pressure needs to be around 1010 mb to suggest that a low may be forming.

One interesting thing to note is that 97L is still moving around 20 mph to the west, while the blob just east of the islands continues to be stationary. If the two interact, a tropical system can develop.


Thats what exactly I think when just wake up and saw the Sat loops.But 97L still like 800 miles aprox. of the Carr. wave, that will take 97L 48hrs aprox. to reach it if continue moving at 20mph west.
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We're hoping for some good surfing waves here in the south coast of Puerto Rico.
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361. CUBWF
Why I can't see Patrap an others posts. Are they banned or something?
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Quoting VAbeachhurricanes:


its 4:31 where the wave is and Dmax is around 6 or 7 therefore it is near and approaching DMAX. thank you


6 is DMIN, not max. MAX is near 5 am local time.

Thank you.
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358. CUBWF
Thanks VAbeach
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Found this link explaining Herbert's Box http://www.hurricanecity.com/hebertbox.htm - sharing in case anyone else was looking for more info like me
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97L Water Vapor (IR3)
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Quoting CUBWF:
Hello everybody. First time I post. Reading the blog for a time. Learning something new every season. Sorry for my english. I know is not the best. I'll try to understand. Please, be patient on my questions. LOL


Well Welcome aboard! feel free to ask questions thats why we are all here is too learn. Most of us dont bite :)
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Tracking Info For Invest 97


Time Lat Lon Wind(mph) Pressure Storm type
-------------------------------------------------------------
12 GMT 07/17/09 12.0N 34.7W 20 1012 Invest
18 GMT 07/17/09 12.0N 36.0W 20 1012 Invest
00 GMT 07/18/09 11.5N 38.0W 20 1013 Invest
12 GMT 07/18/09 11.9N 41.8W 20 1013 Invest
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Quoting VAbeachhurricanes:


its 4:31 where the wave is and Dmax is around 6 or 7 therefore it is near and approaching DMAX. thank you


That is totally incorrect lol. we are approaching DMIN, not DMAX
Please post links when yousee something, ie radar image down there, thanks
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Quoting JRRP:
RIP 97L ?


yep
Member Since: March 19, 2009 Posts: 0 Comments: 1421

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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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