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 Weather456:
tropicfreak is correct, low shear as the trough split occurs



Currently the Eastern CONUS is experiencing seasonable cool temperatures thanks in part to a trough dipping across the region. However, this trough will also be involved in initiating a tropical cyclone next week. A trough split situation is expected to coincide with the arrival of the wave as it enters the Western Atlantic. Most models are indicating that the trough will continue to dig south and amplify until a cut-off low forms over the GOM and heads SW. While this occurs, a ridge builds east of this trough split over the SW ATL while at the same the tropical wave will moving through the area. Most of the reliable global models indicate this will spark cyclogenesis and the slow will ride up the USA east of the aforementioned upper trough. During this time, shear is expected to be around 5-15 knots and SSTs are already well above 26C. It seems the next invest will likely be the tropical wave near the islands.





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



not updateing any more


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.
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Maybe it turns out that i am correct. But still feel sorry for drak, I shouldn't have gone off on him.
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It Moving west at 23mph
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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.


Looks like it is going due west.
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Quoting tropicfreak:
Sorry for my out burst. I should of checked before I went off on someone.


ah, nope, you were correct as W456 pointed out apparently. LOL i should have checked myself so i apologize.
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Quoting KEEPEROFTHEGATE:
some clouds a little breeze with rain drops


Actually there 2 deep bursts of convection, will be watched tonight for maybe regeneration.
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Quoting MasterOfStorms:



not updateing any more
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Floater 1- Visible Loop

By running the Caribbean Loop above on Fast,one can see the Circulation west of the Leewards in the Caribbean.

Its easily discernible,and not rocket science.

LOL
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Sorry for my out burst. I should of checked before I went off on someone.
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Member Since: Posts: Comments:
tropicfreak is correct, low shear as the trough split occurs



Currently the Eastern CONUS is experiencing seasonable cool temperatures thanks in part to a trough dipping across the region. However, this trough will also be involved in initiating a tropical cyclone next week. A trough split situation is expected to coincide with the arrival of the wave as it enters the Western Atlantic. Most models are indicating that the trough will continue to dig south and amplify until a cut-off low forms over the GOM and heads SW. While this occurs, a ridge builds east of this trough split over the SW ATL while at the same the tropical wave will moving through the area. Most of the reliable global models indicate this will spark cyclogenesis and the slow will ride up the USA east of the aforementioned upper trough. During this time, shear is expected to be around 5-15 knots and SSTs are already well above 26C. It seems the next invest will likely be the tropical wave near the islands.



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Quoting GeoffreyWPB:


It probally will take off the yellow circle of ex-97 and keep the yellow on the Antilles wave.


I will bet they still have 2 yellow circles.
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Quoting chandelier:
I heard 97L was no longer an invest....what is it now?
some clouds a little breeze with rain drops
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As a rule,it always a good Idea to read the TWO ,or the TWD before rambling.


NHC Page

Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 181758
TWDAT
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Hello. We are about to get a good storm in Boca Raton!
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Quoting leftovers:
almost looks as if a anti cyclone is building over the tw near windwards.


Been wondering the same thing lo, but out of my league, need one of the resident experts to chime in.
Member Since: August 17, 2005 Posts: 26 Comments: 16241
Quoting chandelier:
I heard 97L was no longer an invest....what is it now?


An Ex-Invest.
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Quoting GeoffreyWPB:


It probally will take off the yellow circle of ex-97 and keep the yellow on the Antilles wave.
wunder twins will deactivate both will be gone
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Quoting MasterOfStorms:
97l making a comeback tstms tops cooling

as I said
Quoting wunderkidcayman:

maybe it will be re-instated as tropical Invest 97l
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Quoting reedzone:


Which is why models show "Subtropical" features, not purely Tropical. It's on the cyclone phase maps, it's a good tool.


either way, tropicfreak is still mistaken because he said "shear will lessen in front of the system" not "a system will form in the bahamas"
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I heard 97L was no longer an invest....what is it now?
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Tropical Floater Imagery

Notice the absence of AL 97
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Quoting AllStar17:
It will be interesting to see what the NHC says at the 8 pm TWO


It probally will take off the yellow circle of ex-97 and keep the yellow on the Antilles wave.
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Quoting MasterOfStorms:
97l making a comeback tstms tops cooling



its not 97L any more its X 97L
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97l making a comeback tstms tops cooling
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Quoting BurnedAfterPosting:


actually you are wrong, shear will not decrease in the bahamas, only in the Caribbean

How about you check your facts before you go off on someone. Just a suggestion


Which is why models show "Subtropical" features, not purely Tropical. It's on the cyclone phase maps, it's a good tool.
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It will be interesting to see what the NHC says at the 8 pm TWO
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Thank You. For those of us trying to learn and catch on, it makes it kind of hard when everyone is going different directions, is all. LOL.
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Quoting tropicfreak:


For the thousanth time SHEAR WILL DECREASE AHEAD OF THIS SYSTEM!!!!, look at the models!


Uh, wrong answer. Shear is moving OUT of the caribbean and INTO the bahamas. thats where the blob is supposed to go. Shear is decreasing in former 97L's path, but i dont see much coming out of it.

EDIT: Also, even if the models decreased the shear in this system's path, the models aren't everything. The models predicted perfect conditions for 93L. Each and every one of them were wrong. Of course that means they could be wrong now and it could be favorable in the bahamas but not likely.
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Quoting MasterOfStorms:
tstms continue to refire with 97l,its still an invest just my opinion.

maybe it will be re-instated as tropical Invest 97l
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Quoting tropicfreak:


For the thousanth time SHEAR WILL DECREASE AHEAD OF THIS SYSTEM!!!!, look at the models!


actually you are wrong, shear will not decrease in the bahamas, only in the Caribbean

How about you check your facts before you go off on someone. Just a suggestion
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Quoting sebastianflorida:
No, do not honor thy self, it was not directed towards you or anyone in particular! Mainly the children on here that act very immature. I respect your feedback though.


Ok, no problem :)
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765. JRRP
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764. JRRP
.
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No, do not honor thy self, it was not directed towards you or anyone in particular! Mainly the children on here that act very immature. I respect your feedback though.
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Quoting Drakoen:
Shear in the Bahamas looks to stay unfavorable. An east coast storm has a better chance a being a subtropical entity as it interacts with a frontal boundary and an upper level trough.


For the thousanth time SHEAR WILL DECREASE AHEAD OF THIS SYSTEM!!!!, look at the models!
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I see things still haven't changed on here
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To all of you eloquent and educated weather persons out there posting excellent graphics and wx quotes from the NWS, I thank you. For my own decision process. I look at all the maps and graphics, see all those blobs and trails and pretty colors, and figure something is going to happen, if not right now then pretty soon. I even think I see a rotation in the clouds below the gulf coast. Wouldn't that suck if one of those eddies that broke off the gulf stream a while back is still out there heatingup enough to trigger some convection. Anyway just my comments from the low tech side of the blog.
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Quoting ArmyWifeInGa:
Could someone please show confirmation of 97L and 98L if they do or don't exist please.


the BAMMS and other models like that stopped running on the invest after 12Z. that's what proved me that they dropped it, not that one post that people believed first.
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Quoting ArmyWifeInGa:
Could someone please show confirmation of 97L and 98L if they do or don't exist please.
97L deactivated and no 98L as yet.
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Quoting sebastianflorida:
COULD NOT HAVE SAID IT BETTER! TOO MANY ON THE BLOG ARE CHILDREN PRETENDING TO BE HEROIC METEROLOGIST. FOR THOSE THAT WANT TO LEARN, ARE OVER 18, AND DO NOT PLAY GAMES ON THIS BLOG, THERE ARE MANY OF US THAT APPRECIATE YOUR PARTICIPATION> ALL OTHERS, PLEASE POOF ME OR WHATEVER YOU CALL IT, CAUSE I AM HERE TO LEARN AND STAY UPDATED WITH THE FACTS, NOT YOUR BICKERING AND WISHCASTING.

THANK YOU


I'm 20 years old, turning 21 in November. I'm not trying to be heroric, heck I'm not perfect. We all mess up on our forecast, Drakeon, Weather456, StormW, and even Dr. Masters. I have studied storms for years, since Hurricane Floyd hit my hometown in NY 10 years ago. I've had good and bad predictions, I nailed Rita in 2005, and also predicted Humberto to reach at least 65-70 mph. when it became a Tropical Storm because of how fast it was intensifying. I'm not trying to be a hero and I KNOW this post was directed towards me because I kept and still keep on saying to watch whatever's left of 97L. We are in Hurricane Season, the remnants of 97L are sort of trying to regenerate right now, and the Tropical Wave that fascinated everybody has model support. I'm not a wishcaster, I predict by pattern and some models. That's all I'm gonna say about that post.
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Could someone please show confirmation of 97L and 98L if they do or don't exist please.
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Not at the moment, but it is too much and daily.
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tstms continue to refire with 97l,its still an invest just my opinion.
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Quoting sebastianflorida:
COULD NOT HAVE SAID IT BETTER! TOO MANY ON THE BLOG ARE CHILDREN PRETENDING TO BE HEROIC METEROLOGIST. FOR THOSE THAT WANT TO LEARN, ARE OVER 18, AND DO NOT PLAY GAMES ON THIS BLOG, THERE ARE MANY OF US THAT APPRECIATE YOUR PARTICIPATION> ALL OTHERS, PLEASE POOF ME OR WHATEVER YOU CALL IT, CAUSE I AM HERE TO LEARN AND STAY UPDATED WITH THE FACTS, NOT YOUR BICKERING AND WISHCASTING.

THANK YOU
Did I miss something ? Who is bickering ?
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Just like yesterday Drak...going to be noisy and nasty for a bit.
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18Z GFS starting to lock more and more into a Bahama to E FL coast low development... this time taking it straight up the US E Coast... compared to the last run (12Z) in has trended W in the later period.

Due to current southern location of the current tropical disturbances I would go with a more S and W track of this possible disturbance next week until I see a different behavior that would change my though. I still believe like before that this would be moving right through the Greater Antilles if not a bit further south hugging the coast before starting to turn NW/N/NE due to the split trough that most models are forecasting to be in place in the C 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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