Dr. Jeff Masters' WunderBlog

Two African waves worth mentioning
Posted by: Dr. Jeff Masters, 3:51 PM GMT op 18 juli 2009 +2
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
Categories: Hurricane
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2151. IKE 3:22 PM GMT op 19 juli 2009    
Quoting stormdude77:


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

I may upgrade to "C"...
Member Since: 9 juni 2005 Posts: 23 Comments: 37044
2152. CaneWarning 3:23 PM GMT op 19 juli 2009    
I just wish they'd run the HWRF and GFDL models...
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2153. Drakoen 3:23 PM GMT op 19 juli 2009    
Member Since: 28 oktober 2006 Posts: 57 Comments: 29010
2154. extreme236 3:24 PM GMT op 19 juli 2009    
Quoting IKE:


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

I may upgrade to "C"...


It looks rather impressive.
Member Since: 2 augustus 2007 Posts: 19 Comments: 19234
2155. weatherwatcher12 3:24 PM GMT op 19 juli 2009    
Quoting IKE:
Looks to me like the center may go just north of Barbados...

If it does that could be trouble for me
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2156. IKE 3:24 PM GMT op 19 juli 2009    
Quoting Drakoen:


wow~
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2157. alaina1085 3:24 PM GMT op 19 juli 2009    
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 :)
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2158. stormwatcherCI 3:24 PM GMT op 19 juli 2009    
Quoting weatherwatcher12:

If it does that could be trouble for me
me too
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2159. IKE 3:25 PM GMT op 19 juli 2009    
Quoting weatherwatcher12:

If it does that could be trouble for me


What island....longitude?
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2160. STORMMASTERG 3:25 PM GMT op 19 juli 2009    
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.
2161. WxLogic 3:25 PM GMT op 19 juli 2009    
Quoting CaneWarning:
I just wish they'd run the HWRF and GFDL models...


To see how it explodes?... hehe...
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2162. centex 3:25 PM GMT op 19 juli 2009    
B as of now, maybe C by 2PM.
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2163. Chicklit 3:25 PM GMT op 19 juli 2009    
Good Morning!
I see we have 97L again.
It's looking much better today.
Member Since: 11 juli 2006 Posts: 14 Comments: 10254
2164. SavannahStorm 3:25 PM GMT op 19 juli 2009    
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.
Member Since: 22 september 2005 Posts: 18 Comments: 2135
2165. CaneWarning 3:25 PM GMT op 19 juli 2009    
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.
Member Since: 26 april 2009 Posts: 3 Comments: 3667
2166. jurakantaino 3:26 PM GMT op 19 juli 2009    
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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2167. alaina1085 3:26 PM GMT op 19 juli 2009    
Morning Chicklit... yup the comeback kid as Ike said. lol.
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2168. CaneWarning 3:26 PM GMT op 19 juli 2009    
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.
Member Since: 26 april 2009 Posts: 3 Comments: 3667
2169. IKE 3:26 PM GMT op 19 juli 2009    
System is quite impressive with each new frame. The outflow/appearance has really improved.
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2170. weatherwatcher12 3:27 PM GMT op 19 juli 2009    
B
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2171. alaina1085 3:27 PM GMT op 19 juli 2009    
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.
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2173. moonlightcowboy 3:28 PM GMT op 19 juli 2009    
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: 9 juli 2006 Posts: 179 Comments: 28118
2174. stormwatcherCI 3:28 PM GMT op 19 juli 2009    
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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2175. pottery 3:28 PM GMT op 19 juli 2009    
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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2176. WxLogic 3:28 PM GMT op 19 juli 2009    
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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2177. stormwatcherCI 3:28 PM GMT op 19 juli 2009    
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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2178. STORMMASTERG 3:29 PM GMT op 19 juli 2009    
If this system develops,i think twc will be emberessed.Esecially after lyons saying upper winds are to strong.
2179. WxLogic 3:29 PM GMT op 19 juli 2009    
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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2180. Grothar 3:29 PM GMT op 19 juli 2009    
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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2181. BurnedAfterPosting 3:29 PM GMT op 19 juli 2009    
ok be back in a few minutes
2182. stormwatcherCI 3:30 PM GMT op 19 juli 2009    
Quoting IKE:


What island....longitude?
He is in Jamaica
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2183. PensacolaBuoy 3:31 PM GMT op 19 juli 2009    
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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2184. moonlightcowboy 3:30 PM GMT op 19 juli 2009    
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: 9 juli 2006 Posts: 179 Comments: 28118
2185. dearmas 3:30 PM GMT op 19 juli 2009    
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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2186. weatherman874 3:31 PM GMT op 19 juli 2009    
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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2187. Cavin Rawlins 3:31 PM GMT op 19 juli 2009    
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.
Member Since: 24 juli 2005 Posts: 407 Comments: 19076
2188. STORMMASTERG 3:32 PM GMT op 19 juli 2009    
I say high chance of ts by tomorrow,this thing looks better than some tds in the past.
2189. sporteguy03 3:32 PM GMT op 19 juli 2009    
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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2190. TampaMishy 3:32 PM GMT op 19 juli 2009    
Isn't it kind of early to be predicting where 97L is heading?
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2191. WxLogic 3:32 PM GMT op 19 juli 2009    
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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2192. HurricaneSwirl 3:32 PM GMT op 19 juli 2009    


invest 97L this time yesterday



invest 97L right now
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2193. robie1conobie 3:32 PM GMT op 19 juli 2009    
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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2194. Drakoen 3:32 PM GMT op 19 juli 2009    
Brennan is a PhD. I'm still going to go with orange.
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2195. moonlightcowboy 3:33 PM GMT op 19 juli 2009    
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: 9 juli 2006 Posts: 179 Comments: 28118
2196. FTLGUY 3:33 PM GMT op 19 juli 2009    
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.
Member Since: 11 september 2007 Posts: 0 Comments: 326
2197. Drakoen 3:33 PM GMT op 19 juli 2009    
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!
Member Since: 28 oktober 2006 Posts: 57 Comments: 29010
2198. wunderkidcayman 3:35 PM GMT op 19 juli 2009    
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: 13 juni 2009 Posts: 2 Comments: 5444
2199. WxLogic 3:35 PM GMT op 19 juli 2009    
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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2200. claimsadjuster 3:36 PM GMT op 19 juli 2009    
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"
2201. SavannahStorm 3:36 PM GMT op 19 juli 2009    
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


B
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About JeffMasters
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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