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 wunderkidcayman:
ok vote
A it becomes a td at the 8:00pm update
B it becomes a td tomorrow updates
C it becomes a td tuesday
D it dosen't become anything but the invest that it is now
E it becomes ts ana in any of the above dates


I vote "E"
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2199. WxLogic
Quoting Drakoen:
Brennan is a PhD. I'm still going to go with orange.


Ohh so after looking up some credentials you then decide now... hehe.
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ok vote
A it becomes a td at the 8:00pm update
B it becomes a td tomorrow updates
C it becomes a td tuesday
D it dosen't become anything but the invest that it is now
E it becomes ts ana in any of the above dates
Member Since: Posts: Comments:
2197. Drakoen
Quoting Grothar:
I agree 97L is looking much better in the GOES images. Most sites agree about less wind sheer. However, does anyone have any information on the Saharan dust and the effect it may have on the system. It has been very hazy here in S. Fla and through the Caribbean. Welcome back Drak. This is only my second day on this bog, but have always enjoyed your comments.


Thanks! Appreciate it!
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2196. FTLGUY
Kind of a "Big" leap for the NHC to pull the plug on 97L yesterday?

Quoting PensacolaBuoy:
I vote "C - red" because I think it's already closing off a circulation. "B" voters are probably right, though. The NHC likes to move in "one small step" instead of leaps-- like when they need to move a forecast track a lot but do it over two or three advisories.
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Quoting Grothar:
However, does anyone have any information on the Saharan dust and the effect it may have on the system.


SAL is no longer a factor. Plenty of moisture in the area and it's creating good lift now on its own.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
2194. Drakoen
Brennan is a PhD. I'm still going to go with orange.
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for as smart as some of you are with weather; I am going out on a limb to say there are not too many spelling bee champs in here!
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invest 97L this time yesterday



invest 97L right now
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2191. WxLogic
Quoting Grothar:
I agree 97L is looking much better in the GOES images. Most sites agree about less wind sheer. However, does anyone have any information on the Saharan dust and the effect it may have on the system. It has been very hazy here in S. Fla and through the Caribbean. Welcome back Drak. This is only my second day on this bog, but have always enjoyed your comments.


In my opinion SAL will no longer be an issue for this system... since the SAL that has traversed through the CARIB and now in the S GOM has been decreasing and/or moving into the EPAC.
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Isn't it kind of early to be predicting where 97L is heading?
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Quoting Grothar:
I agree 97L is looking much better in the GOES images. Most sites agree about less wind sheer. However, does anyone have any information on the Saharan dust and the effect it may have on the system. It has been very hazy here in S. Fla and through the Caribbean. Welcome back Drak. This is only my second day on this bog, but have always enjoyed your comments.


The Dust is pretty much gone out ahead of it the prior wave was like a sponge and absorbed most of it.
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I say high chance of ts by tomorrow,this thing looks better than some tds in the past.
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Quoting STORMMASTERG:
If this system develops,i think twc will be emberessed.Esecially after lyons saying upper winds are to strong.


Only the TWC? I can think of a few others. But heck we are all humans, I have been wrong with 93L, and the world hasn't ended.
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C, unless the hurricane center is being conservative it has clear banding and rotation and has a high likelihood of being a tropical depression
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2185. dearmas
Quoting CaneWarning:
I will say one of our mets in Tampa said the west coast of Florida would have to watch this one if anything got going. He said we had a southwest flow over the state. Now, was he just saying it so you'd watch the news the next time its on? Maybe... But, he is right, I think we are under a southwest flow right now.


which met??
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Quoting pottery:
Hmmmmm, not sure about passing north of Barbados. But deffinitely north of Trinidad.


Hey, Pottery. That was my thinking too last evening. But, if it's getting its act together, the natural coriolis initially would nudge it a few degrees north even, despite steering I believe.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
I vote "C - red" because I think it's already closing off a circulation. "B" voters are probably right, though. The NHC likes to move in "one small step" instead of leaps-- like when they need to move a forecast track a lot but do it over two or three advisories.
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Quoting IKE:


What island....longitude?
He is in Jamaica
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ok be back in a few minutes
2180. Grothar
I agree 97L is looking much better in the GOES images. Most sites agree about less wind sheer. However, does anyone have any information on the Saharan dust and the effect it may have on the system. It has been very hazy here in S. Fla and through the Caribbean. Welcome back Drak. This is only my second day on this bog, but have always enjoyed your comments.
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2179. WxLogic
Quoting pottery:
Hmmmmm, not sure about passing north of Barbados. But deffinitely north of Trinidad. May get some showers here. Would love some heavy rain.


Hehe... Pot... be careful for what you wish!!!
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If this system develops,i think twc will be emberessed.Esecially after lyons saying upper winds are to strong.
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Quoting stormwatcherCI:
I only meant folks like you,456, Drak and whoever might know more than me which is just about everyone on here. I only go by what it "looks" like to me.
Ooops and Ike
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2176. WxLogic
Quoting IKE:
System is quite impressive with each new frame. The outflow/appearance has really improved.


If it's able to take full advantage of the current low shear conditions and warm SSTs then it should be able to fight off any low enough shear... say 20k or less and still keep its identity.
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2175. pottery
Hmmmmm, not sure about passing north of Barbados. But deffinitely north of Trinidad. May get some showers here. Would love some heavy rain.
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Quoting Drakoen:


There are no PhD's in here lol
I only meant folks like you,456, Drak and whoever might know more than me which is just about everyone on here. I only go by what it "looks" like to me.
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Quoting SavannahStorm:


They have never been run on 97L, even the first time it was named an invest. Maybe now they'll make it a priority.


I'm not very concerned with the global models at this stage, especially not the GFDL which is very poor in the cyclogenesis phase. I think the LBAR and BAMS more accurately depict what's happening in its present phase of development...and just good ol' natural "seeing is believing" look as sats, etc, than models.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Quoting IKE:
System is quite impressive with each new frame. The outflow/appearance has really improved.


Agreed. That's why I asked about the rapid intensification.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
B
Member Since: May 16, 2009 Posts: 1 Comments: 1231
2169. IKE
System is quite impressive with each new frame. The outflow/appearance has really improved.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting SavannahStorm:


They have never been run on 97L, even the first time it was named an invest. Maybe now they'll make it a priority.


I know, I just wonder why not though.
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Morning Chicklit... yup the comeback kid as Ike said. lol.
Member Since: August 2, 2006 Posts: 0 Comments: 1240
Agree, and thank you "burneafterposting", learn a lot from your "posting".You were the only one that base in your knowledge made an accurate forecast.
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I will say one of our mets in Tampa said the west coast of Florida would have to watch this one if anything got going. He said we had a southwest flow over the state. Now, was he just saying it so you'd watch the news the next time its on? Maybe... But, he is right, I think we are under a southwest flow right now.
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Quoting CaneWarning:
I just wish they'd run the HWRF and GFDL models...


They have never been run on 97L, even the first time it was named an invest. Maybe now they'll make it a priority.
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Good Morning!
I see we have 97L again.
It's looking much better today.
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2162. centex
B as of now, maybe C by 2PM.
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2161. WxLogic
Quoting CaneWarning:
I just wish they'd run the HWRF and GFDL models...


To see how it explodes?... hehe...
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This is no suprise to me this storm is getting better organized.It looked good tonight in 10kt shear.Now its entered the 5kt zone.
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2159. IKE
Quoting weatherwatcher12:

If it does that could be trouble for me


What island....longitude?
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Quoting weatherwatcher12:

If it does that could be trouble for me
me too
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Quoting Weather456:
Notice the convective band ahead of 97L is not being sheared. That is a trick I learn back in 04. That signals potential for continued development of this system.


Thanks 456, I was noticing that as well. Good tip :)
Member Since: August 2, 2006 Posts: 0 Comments: 1240
2156. IKE
Quoting Drakoen:


wow~
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
Looks to me like the center may go just north of Barbados...

If it does that could be trouble for me
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting IKE:


If that isn't a "B", then I need new glasses.

I may upgrade to "C"...


It looks rather impressive.
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2153. Drakoen
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I just wish they'd run the HWRF and GFDL models...
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2151. IKE
Quoting stormdude77:


If that isn't a "B", then I need new glasses.

I may upgrade to "C"...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2150. beell
B
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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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