Dr. Jeff Masters' WunderBlog

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	New African disturbance 96L likely to develop

Posted by: JeffMasters, 2:55 PM GMT on September 07, 2009

A tropical wave (96L) that emerged off the coast of Africa yesterday has organized rather quickly, and will likely become a tropical depression by Tuesday night. Satellite imagery from the European satellite shows a well-organized circulation, but not enough heavy thunderstorm activity near the center of circulation to be considered a tropical depression. The storm is far enough south that the dry air of the Saharan Air Layer is not a major impediment to development. Wind shear is moderate, 10 - 15 knots, and ocean temperatures are 1 - 2°C above the threshold needed for tropical cyclone formation.

Figure 1. Morning satellite image of 96L, off the coast of Africa. The remains of disturbance 95L, which are under 30 - 40 knots of wind shear, can be seen at upper left.

The forecast for 96L
Most of the models develop 96L, and the chances are that this disturbance will become Tropical Storm Fred later this week. The system will initially move west-northwest, but by Thursday, a strong trough of low pressure passing to 96L's north will pull the storm to the northwest, and may be capable of fully recurving the storm to the northeast. However, most of the models foresee that 96L will not move far enough north for this to happen, and that the storm will have to wait for the next trough of low pressure. With the steering pattern for this year continuing to feature plenty of deep troughs of low pressure moving off the U.S. East Coast, the odds of 96L making it all the way across the Atlantic to threaten land areas appear low. Still, much that is unexpected can and does happen in the world of tropical meteorology, and 96L bears watching.

North Carolina low
An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain to eastern North Carolina today and Tuesday, as the storm slides north-northeastward along the coast.

I'll have an update Tuesday.

Jeff Masters

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651. Patrap 7:54 PM GMT on September 07, 2009
Im so confused..is it 96L,0L7, 007,or TD-7..and should I sauce the Chicken again or start the wienies? The Shrimps are beginning to Burl too. Smells like a Holiday here. Member Since: July 3, 2005 Posts: 377 Comments: 112912

653. StormSurgeon

This comment has been removed for violating the Community Standards.

654. ElConando 7:55 PM GMT on September 07, 2009
Ike you got mail you understand when you read it. Member Since: September 6, 2009 Posts: 2 Comments: 3709

655. Levi32 7:55 PM GMT on September 07, 2009
Quoting Ameister12: I think 15E might be going under rapid intensification. There seems to be an eye like feature. An eye-like feature like that is more likely caused by dry air messing with its inner structure. Notice the stratocumulus field to the NW on that image. That's indicating a dry and stable airmass associated with cool SSTs. Strengthening of 15E is unlikely. Member Since: November 24, 2005 Posts: 593 Comments: 25600

656. Drakoen 7:55 PM GMT on September 07, 2009
Ensemble members continue to feature the system heading back west or even WSW. Member Since: October 28, 2006 Posts: 57 Comments: 29012

657. TheDawnAwakening 7:55 PM GMT on September 07, 2009
If future Fred can develop into a strong cyclone and a large cyclone and the low to the north is weak enough, then Fred could continue to move westward and not be influenced by the low. Member Since: October 21, 2008 Posts: 215 Comments: 3159

658. weatherblog 7:58 PM GMT on September 07, 2009
Quoting TheDawnAwakening: Where is the blog? I mean there should be a lot of activity during the peak of hurricane season with a newly developing tropical cyclone now. I agree, but the reason there isn't is because apparently 96L looks to be going out to sea. That's why there's more talk of a sheared disturbance in the GOM that'll probably never form than TD 7. Member Since: July 10, 2006 Posts: 27 Comments: 1623

659. Tazmanian 7:56 PM GMT on September 07, 2009
what is this a wather blog or guss on WS blog?? Member Since: May 21, 2006 Posts: 5089 Comments: 111610

660. Weather456 7:57 PM GMT on September 07, 2009
Quoting Ameister12: I think 15E might be going under rapid intensification. There seems to be an eye like feature. unlikely when ever a tropical cyclone moves into a stratocumulus field in signifies it is moving to a stable environment Member Since: July 24, 2005 Posts: 407 Comments: 19076

661. Weather456 7:57 PM GMT on September 07, 2009
Hello Levi! Member Since: July 24, 2005 Posts: 407 Comments: 19076

662. TheDawnAwakening 7:58 PM GMT on September 07, 2009
Drak, the ensembles could be on to something. With a potentially stronger system it could continue west without any effects felt from the upper level low to the north. Since 07L is developing Spiral banding it has the conditions favorable for possible a little more rapid intensification as well as the lowering of the minimum central pressure. Erika never had spiral banding. Member Since: October 21, 2008 Posts: 215 Comments: 3159

663. weatherblog 7:59 PM GMT on September 07, 2009
Quoting Drakoen: Ensemble members continue to feature the system heading back west or even WSW. Do you think that scenario is possible or are you thinking otherwise? Member Since: July 10, 2006 Posts: 27 Comments: 1623

664. cchsweatherman 7:59 PM GMT on September 07, 2009
Quoting Drakoen: Ensemble members continue to feature the system heading back west or even WSW. The GFS ensembles have continued to be persistent in showing this trend. In my experience, the ensembles usually do rather well in showing future general trends, so this is quite interesting. Member Since: April 14, 2007 Posts: 8 Comments: 4928

665. ElConando 7:59 PM GMT on September 07, 2009
Quoting ElConando: Ike you got mail you understand when you read it. Member Since: September 6, 2009 Posts: 2 Comments: 3709

666. SevereHurricane 7:59 PM GMT on September 07, 2009
Welcome back Levi! Member Since: September 7, 2008 Posts: 17 Comments: 1604

667. cyclonekid 7:59 PM GMT on September 07, 2009
From the NRL website...96L has become TD 7 and TD 15E is now TS Linda. IT IS OFFICIAL!!!! clapping Member Since: July 14, 2009 Posts: 51 Comments: 1659

668. NARCHER 7:59 PM GMT on September 07, 2009
Quoting cchsweatherman: TROPICAL DEPRESSION SEVEN 18Z Statistical Model Runs 18Z Early Dynamical Model Runs don't waist your time on this one. in a normal season yeas but this is going to the north in 72hr will need your talent later maybe in oct when the us may get a threat.

669. Levi32 7:59 PM GMT on September 07, 2009
Quoting Weather456: Hello Levi! Hey there 456 :) Member Since: November 24, 2005 Posts: 593 Comments: 25600

670. TheDawnAwakening 7:59 PM GMT on September 07, 2009
07L has the potential to pull an Ike. I believe the models see a high pressure system building swward. Member Since: October 21, 2008 Posts: 215 Comments: 3159

671. Drakoen 8:01 PM GMT on September 07, 2009
Quoting TheDawnAwakening: Drak, the ensembles could be on to something. With a potentially stronger system it could continue west without any effects felt from the upper level low to the north. Since 07L is developing Spiral banding it has the conditions favorable for possible a little more rapid intensification as well as the lowering of the minimum central pressure. Erika never had spiral banding. That is true and the ensemble GFS usually performs better than the operational GFS. The system would have to increase it's diameter at 500mb to get caught under the ridge earlier. Member Since: October 28, 2006 Posts: 57 Comments: 29012

672. jurakantaino 8:00 PM GMT on September 07, 2009
Quoting presslord: Ameister...we're all weather weenies...extreme nature of most any sort is pretty much fair game...especially when the tropics are kinda quiet... Not quite anymore TD7 is born. Member Since: July 31, 2008 Posts: 0 Comments: 730

673. Ameister12 8:01 PM GMT on September 07, 2009
Quoting Weather456: unlikely when ever a tropical cyclone moves into a stratocumulus field in signifies it is moving to a stable environment I suppose so. But what is with the eye like feature. Member Since: August 9, 2009 Posts: 9 Comments: 3627

674. TheDawnAwakening 8:01 PM GMT on September 07, 2009
The Central Atlantic Ocean infrared imagery is beginning to show 96L's western circulation. I believe by tomorrow the full circulation will be on the satellite imagery. Also there is no active floaters on the SSD site for 96L or 07L. Member Since: October 21, 2008 Posts: 215 Comments: 3159

675. canehater1 8:02 PM GMT on September 07, 2009
My linited knowledge tells me area in SW GOMEX bears watching too see if a surface low develops along this inverted trough..anyoone have any thoughts? Member Since: September 8, 2008 Posts: 1 Comments: 687

676. Dakster 8:02 PM GMT on September 07, 2009
Yay! We have something for all the xxxxCasters to talk about. Member Since: March 10, 2006 Posts: 0 Comments: 5259

677. TheDawnAwakening 8:02 PM GMT on September 07, 2009
Quoting Drakoen: That is true and the ensemble GFS usually performs better than the operational GFS. The system would have to increase it's diameter at 500mb to get caught under the ridge earlier. The circulation at 500mb is pretty strong right now. It is a pretty stacked system. Member Since: October 21, 2008 Posts: 215 Comments: 3159

678. cchsweatherman 8:02 PM GMT on September 07, 2009
Quoting NARCHER: don't waist your time on this one. in a normal season yeas but this is going to the north in 72hr will need your talent later maybe in oct when the us may get a threat. I put forth the same effort with every system since I care about all people out there, not just my local interests. Given the current GFS ensembles, I wouldn't be so quick to definitively say that this will go north. Member Since: April 14, 2007 Posts: 8 Comments: 4928

679. Levi32 8:03 PM GMT on September 07, 2009
Quoting TheDawnAwakening: The Central Atlantic Ocean infrared imagery is beginning to show 96L's western circulation. I believe by tomorrow the full circulation will be on the satellite imagery. Also there is no active floaters on the SSD site for 96L or 07L. They can't put up a GOES-12 floater until the system comes at least mostly into the satellite's view, as you mentioned it's starting to do. Member Since: November 24, 2005 Posts: 593 Comments: 25600

681. futuremet 8:04 PM GMT on September 07, 2009
It is still more likely that TD7 will recurve out to sea, as a series of trough will create weaknesses along the A/B high. I just don't see how it can bypass such a weakness. It can bypass it if the Azores high strengthens back in time, which is why the CMC and other models stalls it and moves it back west. One thing is for sure, the chance of a U.S. impact is low, for the model ensemble shows another prolonged troughing pattern. Member Since: July 19, 2008 Posts: 43 Comments: 4049

682. Drakoen 8:04 PM GMT on September 07, 2009
Quoting weatherblog: Do you think that scenario is possible or are you thinking otherwise? It is possible and while the GFS loses the system's vortex it is showing that possibility as well. The ECMWF, however, continues to take this system out to sea early. That certainly cannot be ignored considering it is one of the best performing models this year. Member Since: October 28, 2006 Posts: 57 Comments: 29012

683. NARCHER 8:05 PM GMT on September 07, 2009
Quoting futuremet: It is still more likely that TD7 will recurve out to sea, as a series of trough will create weaknesses along the A/B high. I just don't see how it can bypass such a weakness. It can bypass it if the Azores high strengthens back in time, which is why the CMC and other models stalls it and moves it back west. One thing is for sure, the chance of a U.S. impact is low, for the model ensemble shows another prolonged troughing pattern. good post

684. Weather456 8:06 PM GMT on September 07, 2009
A series of trough will help pull 96L north. But becuz these are alternating between ridge and trough, a NW motion isnt going to be consistent. From my blog My thinking is that the storm will continue west and take a gradually turn towards the northwest through days 4-5. Afterwhich, the storm may fluctuate between west-northwest and north-northwest through days 5-7 due to successive trough and ridge flows. Member Since: July 24, 2005 Posts: 407 Comments: 19076

686. Drakoen 8:07 PM GMT on September 07, 2009
We'll just have to wait and see how it unfolds Member Since: October 28, 2006 Posts: 57 Comments: 29012

687. cyclonekid 8:10 PM GMT on September 07, 2009
Quoting futuremet: It is still more likely that TD7 will recurve out to sea, as a series of trough will create weaknesses along the A/B high. I just don't see how it can bypass such a weakness. It can bypass it if the Azores high strengthens back in time, which is why the CMC and other models stalls it and moves it back west. One thing is for sure, the chance of a U.S. impact is low, for the model ensemble shows another prolonged troughing pattern. Good Afternoon, futuremet. Member Since: July 14, 2009 Posts: 51 Comments: 1659

688. Levi32 8:10 PM GMT on September 07, 2009
Quoting WeatherStudent: Afternoon, Drak! OMG!!!!!!!!!!!!!!! Levi32, welcome back. We've missed you terribly. Where have you've been? Is everything OK? I'm frolic to have you back. You're extraordinarily intellgent when it comes to the field of tropical meteorology. Anyways, thoughts on TD7?, my bud??? Yipers!!! :) You're back, yes!!!!!! :) Hyper as ever I see WS....lol. If you read my parting blog my family has been doing a lot and with the school year starting I've been a bit too busy to write regular blogs. I'll be trying to stop by in here when I can. As for TD 7 I have no disagreement with the thoughts in here. It's likely to eventually recurve. I'm more excited about the fact that we finally have a true Cape Verde system to watch in the eastern Atlantic. The only reason it's developing so nicely is because of the 2 waves in front of it that paved the way by moistening the atmosphere up. If it weren't for them the dominant dry air would kill 96L just like the other waves before it. Member Since: November 24, 2005 Posts: 593 Comments: 25600

689. Weather456 8:10 PM GMT on September 07, 2009
This is the 2nd of 2 frontal troughs expected in 1 week Member Since: July 24, 2005 Posts: 407 Comments: 19076

690. futuremet 8:10 PM GMT on September 07, 2009
Good to see you cyclonekid Member Since: July 19, 2008 Posts: 43 Comments: 4049

692. Ameister12 8:11 PM GMT on September 07, 2009
Quoting Levi32: An eye-like feature like that is more likely caused by dry air messing with its inner structure. Notice the stratocumulus field to the NW on that image. That's indicating a dry and stable airmass associated with cool SSTs. Strengthening of 15E is unlikely. That makes since. Bye the way, welcome back! Member Since: August 9, 2009 Posts: 9 Comments: 3627

693. rxse7en 8:11 PM GMT on September 07, 2009
Quoting AussieStorm: They taste great, barely any fat but only the hind legs can be eaten. Just had a horrible, horrible image of a plateful of kangaroo buffalo wings. Carry on. Member Since: August 21, 2005 Posts: 0 Comments: 526

694. TheDawnAwakening 8:12 PM GMT on September 07, 2009
The circulations appeared almost stacked at this time. After looking at the -3 hours compared to the +3 hour shear maps from CIMSS I see that there was an upper level low to the southwest of 07L, but at the +3 hours it has weakened completely with a continued upper level anticyclone over the region with diffluent flow aloft signifying conditions favorable for strengthening although rapid intensification is unlikely for 25 knots in 24 hours given that SSTs are lower then the 29C threshold. Wind shear is dying down among the shear axis stretching SW to NE from the Caribbean Leeward Islands to the old disturbance 95L. Some regions are decreasing. Also divergence is kind of weak but they only sampled the western fringes of the cyclone. Member Since: October 21, 2008 Posts: 215 Comments: 3159

695. cyclonekid 8:12 PM GMT on September 07, 2009
Quoting futuremet: Good to see you cyclonekid Good to see you too...been reading your blog a lot...love them...Great Job. Member Since: July 14, 2009 Posts: 51 Comments: 1659

696. stormy2008 8:12 PM GMT on September 07, 2009
Conditions at 41013 as of (3:50 pm EDT) 1950 GMT on 09/07/2009: Wind Direction (WDIR): ESE ( 120 deg true ) Wind Speed (WSPD): 7.8 kts Wind Gust (GST): 9.7 kts Wave Height (WVHT): 6.2 ft Dominant Wave Period (DPD): 7 sec Average Period (APD): 5.2 sec Mean Wave Direction (MWD): SE ( 135 deg true ) Atmospheric Pressure (PRES): 29.79 in Pressure Tendency (PTDY): -0.11 in ( Falling Rapidly ) Air Temperature (ATMP): 78.1 °F Water Temperature (WTMP): 81.1 °F Dew Point (DEWP): 73.0 °F Heat Index (HEAT): 80.6 °F Member Since: August 18, 2008 Posts: 4 Comments: 215

697. FloridaTigers 8:13 PM GMT on September 07, 2009
Yeah, I don't see TD7/Fred making too far west with this prolonged troughing pattern. Member Since: May 17, 2009 Posts: 0 Comments: 559

698. BDADUDE 8:13 PM GMT on September 07, 2009
oh no !! That Reed dude. the Westcaster is going to show up again. He will have this thing headed for New York. Good thing most of us ignore him. Member Since: September 3, 2008 Posts: 0 Comments: 602

699. TheDawnAwakening 8:14 PM GMT on September 07, 2009
Also I see a way that 07L stays south it has more favorable conditions as well as less SAL to deal with. Will 95L did pave the way, it moved so far NW that it died out due to SAL and Wind shear, but 07L is much further south. If it can stay out of the reach of the troughs for now, it has a better chance to strengthen. Member Since: October 21, 2008 Posts: 215 Comments: 3159

701. Weather456 8:15 PM GMT on September 07, 2009
Some heavy convective burst with TD 7 might bring it to Fred as early as tonight Member Since: July 24, 2005 Posts: 407 Comments: 19076

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