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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1850. aquak9
West of 55ºW.

Thank you, nrtiwl!!
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1849. IKE
From inaccuweather...While there is some dry air located off to the north of the system, wind shear should remain minimal the next few days.
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Quoting nrtiwlnvragn:


Could be, but I didn't track it so not sure. Last data on Carlos EP, 04, 2009071618, , BEST, 0, 94N, 1357W

NOGAPS had Calos tracking towards Hawaii
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Quoting aquak9:
ok, 456, I'll go with that, but I thought they could fly a little further east than that for a short trip, one loop and back.

Anybody else?


I remember Bill Proenzna who use to be director at NHC said Recon will fly out as far as needed if there was a threat to land, not sure if that stance has changed but that is what I remember him saying on I think it was Barometer Bob Show.
Member Since: July 7, 2005 Posts: 0 Comments: 5348
Quoting aquak9:


What are the geographical needs/requirements for recon...west of 50º, or is it west of 55º? I can't remember.


Up to four 6-hourly fixes per day when a storm is within 500 nm of landfall and west of 55ºW in the Atlantic.



National Hurricane Operations Plan
Member Since: September 23, 2005 Posts: 14 Comments: 11210
Quoting crownwx:
I'm not totally convinced that 97L will make depression/storm status, especially with the current shear conditions in the Caribbean with up to 40-50 kts of shear near Jamaica. Also, look at the shear forecast for the next 5 days, the raw numbers show 23 knots of shear in 24 hrs and 30 knots of shear in 48 hours and 34 knots of shear in 72 hours. Would like to see if this pans out over the next 12-24 hrs before I completely jump on the development bandwagon. The raw numbers can be found here: Link


You can't use the word shear in this blog its not allowed after last nite......LOL
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morning everyone

Major props to those that hung on to 97L, I was kinda on the fence, while I acknowledged it was dead, I still felt it had a better shot to develop than the area to its west

We will see what happens
1843. aquak9
ok, 456, I'll go with that, but I thought they could fly a little further east than that for a short trip, one loop and back.

Anybody else?
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Morning All 97L is back i see. Looks like Shear is lite at 10-15kts with some stronger in its path...If it stays South it will encounter less Shear...if it moves north in the NW Caribbean the Shear will be higher. The Southern Path is what steering appears to be what the Steering maps show. There is a weakness as it approaches 60W that could turn it more WNW....I would expect it to stay south tho with modest and slow development maybe possible! Shear probably won't change much until it gets to 60W where conditions could improve or could get worse depending on its course of track!
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Accuweather at 8am

As the Dust Settles

Farther east, a more impressive-looking tropical wave is located around 48 west and south of 15 north. Satellite imagery continues to show a well-defined low to mid-level circulation. There are some showers and thunderstorms in association with the system, though they are not widespread around the center with any banding features. While there is some dry air located off to the north of the system, wind shear should remain minimal the next few days. This in combination with increasingly warmer waters the system will encounter will lead to the possibility of some slow development.
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1840. IKE
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Quoting aquak9:


What are the geographical needs/requirements for recon...west of 50, or is it west of 55? I can't remember.


40W, but I stand to be corrected, that's what I can remember.
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The T storm outside my window right now (tropical storm WANNABEONE) looks more impressive than that wave in the carab.
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LOL I just love when people that get bashed and called names are right. reedzone was spot on, props to you man.

ben has been spot on lots of times too, props to you also.

I was right at first but then i changed my prediction to it getting organized but not much more convection. d'oh!
Member Since: July 7, 2008 Posts: 2 Comments: 3237
1836. aquak9
Quoting Weather456:


Knowing the NHC, at most code organge/red, if keeps its current trend. I suspect the NHC to hold out another day, especially if they want a reccon.


What are the geographical needs/requirements for recon...west of 50º, or is it west of 55º? I can't remember.
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Quoting IKE:


The comeback kid.


ROFL
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1834. crownwx
I'm not totally convinced that 97L will make depression/storm status, especially with the current shear conditions in the Caribbean with up to 40-50 kts of shear near Jamaica. Also, look at the shear forecast for the next 5 days, the raw numbers show 23 knots of shear in 24 hrs and 30 knots of shear in 48 hours and 34 knots of shear in 72 hours. Would like to see if this pans out over the next 12-24 hrs before I completely jump on the development bandwagon. The raw numbers can be found here: Link
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1833. IKE
Quoting sporteguy03:
Ike,
What are good comebacks when NHC deactivated 97L and then reactivates it less then 24 hours later? Thanks in Advance lol.


The comeback kid.
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Quoting stoormfury:
it is really frustrating when QSor ASCAT can show you nothing. loking at the sat pics it would appear a surface low is trying to form


QuikSCAT entirely missed the area this morning, so the best bet we can go on is vis images
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Quoting willdunc79:
can anyone also please tell me the current pressure reading on 97L also?


1013
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1828
Sure looks that way.
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Quoting willdunc79:
can anyone also please tell me the current pressure reading on 97L also?


1013 according to best track
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it is really frustrating when QSor ASCAT can show you nothing. loking at the sat pics it would appear a surface low is trying to form
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can anyone also please tell me the current pressure reading on 97L also?
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I wish they move the floater already, there's nothing to see on that emergency room wave.
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wxlogic that low/hybrid system that crosses FL does the model show it moving up the East coast or crossing Fl and then out to sea?
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Quoting Weather456:


I'm not sure, but typically if you have a convective band ahead of a disturbance it idicates conditions ahead support additional thunderstorm development.


I am sure you saw this as well but notice on the visible and infared pictures the pulsing in the center of cloud tops and it is circular and spreading out tells me shear must be low and there might be a low developing there.
Member Since: July 7, 2005 Posts: 0 Comments: 5348
Morning everyone I see 97L made a comeback,
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Quoting GeoffreyWPB:
456...Do you see a possible depression forming before the day is out?


Knowing the NHC, at most code organge/red, if keeps its current trend. I suspect the NHC to hold out another day, especially if they want a reccon.
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Quoting weathermanwannabe:
Back from breakfast......Appreciate the comments as to different systems/conditions but I still think is has a very small window of opportunity before it approaches the sheer areas right around the lesser Antilles which currently run at about 13 to 15N....If it stays south of about 12N, and keeps going due west, it has a better chance at survival IMHO but I don't see it happening if it keeps gaining latitude at the current rate and speed.......We should know the answer by this time tommorow.
I think it encountered higher shear yesterday and still managed a comeback.
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Quoting Weather456:


I'm not sure, but typically if you have a convective band ahead of a disturbance it idicates conditions ahead support additional thunderstorm development.


Interesting, thanks.
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Quoting hurricaneseason2006:
The wave at 65W becomes Ana and moves the United States East Coast, Bill forms from 97L and moves the Caribbean. Cluadette forms a few days later in the Atlantic (FYI, the GFS is predicting a low in the central Atlantic).

So 2004 all over again with Alex, Bonnie and Charley.


There is one tiny detail, what if none forms or what if 97L develops before the 65W wave. But interesting hypothesis you have there. :)
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1817. WxLogic
WRF/NAM is being pretty consistent at developing a pretty tight hybrid low pressure system in the Easter GOM and moving it across the FL Peninsula in approximately the afternoon hours of tomorrow along the trough currently in the GOM and stretching across FL... we'll see what happens with the convection and how it takes shape between later today and tomorrow.
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Quoting alaina1085:
Hey Aussie.

456, is that a band 97L is trying to form?


I'm not sure, but typically if you have a convective band ahead of a disturbance it idicates conditions ahead support additional thunderstorm development.
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456...Do you see a possible depression forming before the day is out?
Member Since: September 10, 2007 Posts: 0 Comments: 11257
Quoting alaina1085:


I agree, they should have waited another 12-24 hrs to pull the plug. Oh well... its 97L again. Now its just a wait and see game. lol.


I'm thinking now that it suddenly got organized enough to get re-tagged right after the TWO, we might be looking at a code orange by 2 p.m. Off to church now, ttyl
Member Since: July 1, 2008 Posts: 13 Comments: 7396
Quoting AussieStorm:


Is that from ex carlos?


Could be, but I didn't track it so not sure. Last data on Carlos EP, 04, 2009071618, , BEST, 0, 94N, 1357W
Member Since: September 23, 2005 Posts: 14 Comments: 11210
Quoting willdunc79:
what are the exact coordinates for 97L reborn so I can plot it on my map please?


124N 502W
Member Since: September 23, 2005 Posts: 14 Comments: 11210
In NO WAY I am calling this another Felix (2007), but it has acted very much like that particular storm.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
Quoting reedzone:


It's the reason why I never called it X-97L, it was blowing up convection and moving into a better environment for development. I never understood why they scrubbed it, the funny thing is, the scrubbed right when it started to get going again.


I agree, they should have waited another 12-24 hrs to pull the plug. Oh well... its 97L again. Now its just a wait and see game. lol.
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Ike,
What are good comebacks when NHC deactivated 97L and then reactivates it less then 24 hours later? Thanks in Advance lol.
Member Since: July 7, 2005 Posts: 0 Comments: 5348
Hey Aussie.

456, is that a band 97L is trying to form?
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Quoting alaina1085:
Morning Joanie :)


Good morning my friend..:) Hope you are well..:)

That blob near the antillies looks like a little rotation there.. any thoughts??
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Quoting alaina1085:


You totally stuck to your guns and called it!


It's the reason why I never called it X-97L, it was blowing up convection and moving into a better environment for development. I never understood why they scrubbed it, the funny thing is, the scrubbed right when it started to get going again.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
Back from breakfast......Appreciate the comments as to different systems/conditions but I still think is has a very small window of opportunity before it approaches the sheer areas right around the lesser Antilles which currently run at about 13 to 15N....If it stays south of about 12N, and keeps going due west, it has a better chance at survival IMHO but I don't see it happening if it keeps gaining latitude at the current rate and speed.......We should know the answer by this time tommorow.
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Quoting nrtiwlnvragn:


Thats CP91, declared early this morning

CP 91 2009071906 BEST 0 98N 1557W 25 1009 DB


Is that from ex carlos?
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From Dr. M blog above

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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.