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High wind shear ripping into 97L

By: Dr. Jeff Masters, 1:49 PM GMT on July 20, 2009

A strong tropical wave (97L) a few hundred miles east of Barbados in the Lesser Antilles Islands has grown less organized today as it tracks west at 15 - 20 mph. The wave is moving underneath an upper-level trough of low pressure, which is bringing 30 knots of wind shear to 97L. While there is a respectable amount of heavy thunderstorm activity associated with 97L, there is no longer any low-level spiral banding or rotation of the cloud pattern. This morning's QuikSCAT pass at 5:35 am EDT showed sustained winds of 35 mph a few hundred miles east of Barbados, but there was no surface circulation evident. The islands of Barbados, St. Vincent and the Grenadines, St. Lucia, and Martinique can expect heavy rain and wind gusts to 50 mph as 97L moves through the Lesser Antilles Islands this afternoon and tonight, but 97L will not become a tropical depression.

Wind shear along the path of 97L is forecast to remain in the high 25 - 35 knot range for at least the next three days. This should prevent further development of 97L, and I expect the disturbance will be gradually torn apart during the next few days. The National Hurricane Center gives 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours. None of the computer models are forecasting any tropical storm development over the next seven days.


Figure 1. Current satellite image of African wave 97L.

I'll have an update Tuesday morning. As 97L moves through the islands, you may want to follow local observations there using our wundermap for the region.

Jeff Masters

Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Quoting WxLogic:


Click on the "Imagen Animada" which is the Loop... is represented by the right orange arrow.


Thanks Wx
This is a good site to bookmark for Carribean weather. Has links to countries weather office.
Quoting canesrule1:
there is a surface low around 80 and 10, some convection around it, check it out...


Just the Columbian Low I believe.
Ike, GFS is not on this morning's model track.
682

NOUS42 KNHC 211230

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

0830 AM EDT TUE 21 JULY 2009

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 22/1100Z TO 23/1100Z JULY 2009

TCPOD NUMBER.....09-054



I. ATLANTIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW LEVEL

INVEST NEAR 29N 76W AT 23/1800Z.


II. PACIFIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.

JWP
Radar doppler P.R Long range Link
Quoting extreme236:


Just the Columbian Low I believe.


Yep, its a semi-permanent feature down there.
2508. Relix
Wait.. what WX? Did the COC move to the ENE? Man... this thing has me crazy haha. It's fun. Love this place =D
Quoting weathermanwannabe:


Looks like, based on the current location of the A-B high, that the PR AOI and Bahamas AOI, regardless of development issues, will be fishes as far as the US is concerned....But, that will not make it any easier for our Friends in the Greater Antilles and the Bahamas.


That depends on how far to the atmosphere this system extends. This morning's images shows an ill-vertically stacked system, with a cut off 500mb vort max far east of the primary vort centre. Now if it becomes as vigorous as the NAM expects it to be, a recurvature is probable.


Steering
2510. Ossqss


2 yellow circles are to become one, so they say ?
Im sorry Im new too this does that mean a plan is going to see whats going on ???
2512. IKE
Quoting weathermanwannabe:


Looks like, based on the current location of the A-B high, that the PR AOI and Bahamas AOI, regardless of development issues, will be fishes as far as the US is concerned....But, that will not make it any easier for our Friends in the Greater Antilles and the Bahamas.


I agree...troughs in the east will kick these 2 on out..........
Hey Orca:

Just the energy in the atmosphere makes the thunderstorms stronger. The weather we have been having is just the effects of normal heating, etc.

A normal thunderstorm can have winds from 20-40 mph. Its like a mini tropical storm all on its own!
possibility of digging trough might pinch off create a ull near fl. this may drag the tw near the bahamas to be pulled nnw into the n.e. states
Quoting IKE:


I agree...troughs in the east will kick these 2 on out..........


Yes definitely....but it could also cause a coastal storm, such as the one shown by the CMC.
ok lets talk about the troughs.. i will make a new map about the troughs on the east coast.
Quoting extreme236:


Just the Columbian Low I believe.


Yesterday the 18Z HWRF inner nest latched onto the Columbian Low at 84 hrs and developed it. Had LOL
Quoting WeatherLoverinMiami:
Im sorry Im new too this does that mean a plan is going to see whats going on ???

Yep. No flights planned today, but they are on standby for tomorrow, just in case. Nothing for-sure planned, though.
2516

No, it would just be another fake.
Quoting WeatherLoverinMiami:
Im sorry Im new too this does that mean a plan is going to see whats going on ???


No; correct me folks if I am wrong....The Planes do not usually go out until NHC declares an actual tropical disturbance, or depression, and, the system is a potential threat to land...........We are not there yet on these areas, and may not get there, given the high sheer and low probability of development at the present time. But, I have to agree with an earlier comment by someone; if the sheer was more favorable, PR/Haiti might be looking at a tropical storm right now but thankfully, that has not occured.
Quoting zoomiami:
Hey Orca:

Just the energy in the atmosphere makes the thunderstorms stronger. The weather we have been having is just the effects of normal heating, etc.

A normal thunderstorm can have winds from 20-40 mph. Its like a mini tropical storm all on its own!


I must admit.. I have seen them in my travels, but I am sure glad we don't get thunder and lightening here... if we see it once every couple of years.. thats more then enough.
Good catch Keep low level invest on 7/23.
2524. Grothar
Both blobs look vigorous. I have a question, which I hope someone can answer. By looking at previous storm tracks, very few systems start in the eastern Caribbean. Which many refer to on this blog as the"grave-yard" However, many have large blow-ups in this region. Does anyone know the reason?
Looks like the GOM is blocked off for some time to come. Nothin's gettin' in there, imo.
Invest 97L is quite a storm, last night the center was completely detached from the convection mass--I thought it was a goner. Due to aid of diurnal maximum, it developed a some convection near the periphery of the LLC to sustain itself. It is now interacting with some cut-off convective fragments exiting DR.
Quoting Ossqss:


2 yellow circles are to become one, so they say ?
i think they just may become one because according to the models projected path and the swift speed of 97L and in contrast the slow moving AOI over the Bahamas, i very well think they will collide.
Quoting weathermanwannabe:


No; correct me folks if I am wrong....The Planes do not usually go out until NHC declares an actual tropical disturbance, or depression, and, the system is a potential threat to land...........We are not there yet on these areas, and may not get there, given the high sheer and low probability of development at the present time. But, I have to agree with an earlier comment by someone; if the sheer was more favorable, PR/Haiti might be looking at a tropical storm right now but thankfully, that has not occured.


Keep posted a low level invest for 7/23 two days away when 97L might be in the Bahamas the NHC might feel at that time a recon flight will be needed due to promixty to Bahamas and SEUSA there is nothing scheduled before hand.
The energy from 97L will enhance the development in the the Bahamas......
Quoting TampaSpin:
The energy from 97L will enhance the development in the the Bahamas......


That is correct.
2531. IKE
Pocket of 20 knot shear near 97L....

I think we will have 98L by Tonight, imo, thoughts, what do you guys think?
2533. NEwxguy
If the troughs in the east were moving west to east I might agree about kicking these out,but the troughs are expected to move up into canada,which may complicate things.And where the Bermuda High sets up which is expected to pump a lot of moisture our way.
2534. IKE
Quoting IKE:
Pocket of 20 knot shear near 97L....

yeah, but it's also surrounded by a large pocket of 40 knot shear!
2536. WxLogic
Based on the 12Z VORT MAX between 850MB and 500MB they have become more pronounced as they head almost due West for now.

Shear has been decreasing but still in the high side of between 25 to 30KTS.

Conditions should become a bit more favorable but fortunately land interaction will prevent any further development from what it has now... unless it moves across the coastal water of DR/Haiti as the VORT MAX loops are suggesting.
I seen the BAhamas developing late last nite about 3am!
Quoting IKE:
looks like the Bahamas AOI is acquiring good vorticity but is it vertically stacked?
Quoting IKE:


both vorticities increasing.. we now have a red and orange. i wonder what will happen when they collide
Circulation just SE of DR

2541. IKE
From the Charleston,SC extended discussion...

"OF NOTE...0Z GUIDANCE DEPICTS A TROPICAL WAVE APPROACHING THE SE
COAST FOR LATE WEEK. THE 0Z GFS PULLS DEEP LAYER MOISTURE DIRECTLY
ONSHORE AND INTO THE FORECAST AREA BY THURSDAY...PRODUCING A VERY
WET PERIOD THROUGH FRIDAY. HOWEVER...THIS OUTLIER SOLUTION WAS NOT
INCORPORATED INTO THIS FORECAST.


AS THE UPPER TROUGH TEMPORARILY WEAKENS THIS WEEKEND...THE ATLANTIC
RIDE SHOULD EXPAND WEST AND PROVIDE A TYPICAL TEMPERATURE/POPS
REGIME.

LATE THIS WEEKEND INTO EARLY NEXT WEEK...ANOTHER UPPER TROUGH WILL
AMPLIFY UPSTREAM OF THE REGION AND WILL PRESS TOWARD THE EAST COAST.

THIS WILL DRIVE ANOTHER COLD FRONT TOWARD THE SE COAST. THERE EXISTS
UNCERTAINTY REGARDING TIMING OF THIS SCENARIO...BUT THE COLD FRONT
COULD EVENTUALLY ENHANCE POPS EARLY NEXT WEEK."
2542. IKE
Quoting HurricaneSwirl:


both vorticities increasing.. we now have a red and orange. i wonder what will happen when they collide


Their not going to collide. They never have since these 2 were east of the islands.
Quoting HurricaneSwirl:


both vorticities increasing.. we now have a red and orange. i wonder what will happen when they collide


The world would end
im sorry but i cant help but laugh at your posts jason, at least he is asking if he can make maps this time lol
Quoting IKE:


Their not going to collide. They never have since these 2 were east of the islands.


oh. im not an expert so i was just going off of what everyone else was saying. other people were saying that parts of 97L were gonna mix in with the bahamas disturbance or something. confusing.
Quoting HurricaneSwirl:


both vorticities increasing.. we now have a red and orange. i wonder what will happen when they collide

One will probably do its best vampire impression, and suck the life out of the other. (ie: They won't collide physically, but just get close enough to interact and combine some energy)
LATEST WRF SHEAR MODEL SHOWS:it shows decreasing shear over all the gulf/caribean as well to 0 to 10kt.
Quoting futuremet:


The world would end


TY futuremet zomg i putting my shutters up right now!1!!
Quoting jeffs713:

One will probably do its best vampire impression, and suck the life out of the other.


LOL. that makes me want to edit a satellite image when wilma and alpha collided.
Quoting HurricaneSwirl:


TY futuremet zomg i putting my shutters up right now!1!!


Somehow, I think that shutters won't do much for the end of the world as we know it. (It's the end of the world as we know it, and I'm doing fiiiine)
2551. Ossqss
From the other TW discussion.

"An analysis of the 850 millibar vorticity field shows that even though Invest 97L is highly disorganized, it does have a good vorticity field with it, which means basically it contains a good amount of potential energy. A second 850 millibar vorticity max can be seen over the extreme southeast Bahamas early this morning. Personally, I think either all of or part of Invest 97L will track into the Bahamas roughly on a path that interconnects those two 850 millibar vorticity maxes that I just spoke of. I believe that this system will be in the Bahamas by about Wednesday night and this is the point where it may encounter more favorable enviornmental conditions and I suspect that something sub-tropical or purely tropical may form over the waters in an area between the northern Bahamas and off of the US Southeast coast by the end of this week."
Can ya'll believe 97L is going at 26mph, damn.
Quoting jeffs713:


Somehow, I think that shutters won't do much for the end of the world as we know it. (It's the end of the world as we know it, and I'm doing fiiiine)


oh im one step ahead of ya.. im taping two giant steel shutters together and gluing them on to my doorstep for good luck
2554. MahFL
Of course you kow the forcast shear can always not occur......then boom... TD 2 and TD 3.....
can someone give me the link for the vorticity map, thanks, i can't find it.
Dr. M should be updating the Blog soon....I suspect he will give both areas around a 20% shot given sheer levels, but, the potential for flooding rains/wind/mudslides for PR/Dominica/Bahamas.
Quoting HurricaneSwirl:


oh im one step ahead of ya.. im taping two giant steel shutters together and gluing them on to my doorstep for good luck


Make sure you can get into your house... ;)
Quoting canesrule1:
can someone give me the link for the vorticity map, thanks, i can't find it.


Link

CIMMS site
I don't expect any thing tropical to form of the us east coast.The shear will retreat,based on wrf it will have 30kt shea rin bahamas.Plus trough will keep it of the coast.
here you go futuremet...

2562. MrSea
Hey wannabe! How've you been, been sailing lately?
Quoting HurricaneSwirl:


Link
thanks again
Quoting jeffs713:


Make sure you can get into your house... ;)


D'OH!
Thanks for the Chas discussion IKE. I've been traveling there for work recently. May have to take the rain gear next week :).
Quoting MrSea:
Hey wannabe! How've you been, been sailing lately?


Actually been doing well, don't sail (you got the right person?), but I do fish.... :)
850MB



700MB



500MB



The system that has better potential is the wave behind 97l.Its gona travel in low shear during its life time.Plus have enhenced dews/and warm ocean temps.I 97l reaches peak td.Shear over the bahamas is to strong/strenghten once trough moves there.
2569. sfla82
I feel alot better with the models for 97L incase it did develop. The models take it away from South Fla!!! Dodged another one. I still dont think 97L will make it that far down the road.
2570. CUBWF
Good morning. Can someone give the link for DR radar.
Both 97L and the AOI over the Bahamas are vertically stacked between 850-500 mb.
2572. MrSea
Quoting weathermanwannabe:


Actually been doing well, don't sail (you got the right person?), but I do fish.... :)


I guess theres another weathermanwannabe out there... perhaps different spelling? lol the guy i knew was like a cargo boat sailor haha

well hows fishing going for ya?

no way...the storm is moving wnw at 26 mph.....
Quoting canesrule1:
thanks again


np, if you need the link to the main site its CIMSS site

just scroll down and put your mouse over north atlantic and click whatever you wanna view
Quoting MrSea:


I guess theres another weathermanwannabe out there... perhaps different spelling? lol the guy i knew was like a cargo boat sailor haha

well hows fishing going for ya?



Too hot right now inshore around the Big Bend so taking the Summer off (doing the Blog thing) and waiting for the Fall for the Reds and Mackarel runs.
Quoting HurricaneSwirl:


np, if you need the link to the main site its CIMSS site

just scroll down and put your mouse over north atlantic and click whatever you wanna view
thanks, i got the site i just didn't know how to get to the vorticity maps.
here are the two yellow circles on the map..

morning all, well I see some interesting developments occured overnight

97L refuses to die LOL

we could have 98L, as I said last night what I think will happen is 97L will help spark something in the Bahamas

Also the wave in the CATL looks good, but well I guess it is going to hit South America lol
Here you can see where the center is....

Link
2582. MrSea
sounds good wannabe

so guys do you think we'll see the bahamas spin become an invest today? i sure hope so

and also, ive been on this blog for the past 3 days now and i dont recall seeing a woman post. decrease in women posting here since last year?

and btw on the AVN loop theres a clearly defined rotation at 16.9N 66.3W
Quoting jasoniscoolman09:
here are the two yellow circles on the map..

very good, now you aren't lying!
Quoting gator23:


Crazy and cool. Tropical Atlantic City
It does sound odd, but New Jersey's coast is considered to have a "humid subtropical" climate. Look on wikipedia.
Quoting canesrule1:
thanks, i got the site i just didn't know how to get to the vorticity maps.


ok i posted it just in case anyways ;)


wow wind shear isn't just high for the atlantic, if you look at the CIMSS site there is a large area of 30-70 knots of wind shear in the east pacific and in the west pacific there are many areas of 30-50 knot wind shear, but the west pacific looks like the most favorable basin right now.
IKE...thanks for the Charleston heads up...today sure is pretty here...
Quoting BurnedAfterPosting:
morning all, well I see some interesting developments occured overnight

97L refuses to die LOL

we could have 98L, as I said last night what I think will happen is 97L will help spark something in the Bahamas

Also the wave in the CATL looks good, but well I guess it is going to hit South America lol



Another day of shear talk and jumping to conclusions ahead :)
Quoting cybergrump:
Here you can see where the center is....

Link


Based on the latest radar images, 97L has actually gotten better organized since last night. The center was completely cut off from the convection. However, it is till ill-vertically stacked.
Interesting language from the NHC on 97L?? "At this time." If 97L can survive the Haiti and DR death trip.......perhaps by Thurs/Fri atmosphere may improve. 2nd blob they may fly into it on the 23rd.
2590. ssmate
Quoting jasoniscoolman09:
here are the two yellow circles on the map..



You'll need more proof than that.
Quoting Gumbogator:
Interesting language from the NHC on 97L?? "At this time." If 97L can survive the Haiti and DR death trip.......perhaps by Thurs/Fri atmosphere may improve. 2nd blob they may fly into it on the 23rd.


I highly doubt both will be able to develop due to their close proximity, one of them yes, but not both.
im looking at the WU wundermap and i see the COC on radar but i have noticed something, this isn't moving WNW its actually moving NW at over 25 mph.
2594. MrSea


I like this. It shows that what is now in the Bahamas region was that wave we saw that was out ahead of 97L, the one that went through the caribbean a couple days ago.

It also shows that 97L is moving NW and probably wont develop until its in the bahamas region as well (itll be over mountainous land too soon for it to develop now)
Leading edge of some of the t-storms starting to come on-shore on the SW coast of PR...
Quoting presslord:
IKE...thanks for the Charleston heads up...today sure is pretty here...


Preslord, I'm surprised you are not tracking this, since the Carolinas may be affected.
Quoting futuremet:


Based on the latest radar images, 97L has actually gotten better organized since last night. The center was completely cut off from the convection. However, it is till ill-vertically stacked.
no, its actually vertically stacked look:

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500 MB

2598. centex
Looks WNW to me and may have some mountains in it's future.
Quoting MrSea:
sounds good wannabe

so guys do you think we'll see the bahamas spin become an invest today? i sure hope so

and also, ive been on this blog for the past 3 days now and i dont recall seeing a woman post. decrease in women posting here since last year?

and btw on the AVN loop theres a clearly defined rotation at 16.9N 66.3W


Surfmom, Chicklet, Alaina, TampaMishy have posted among others
Shear continues to decrease, and this system continues to become more organized. A quasi-CDO seem to established, as the COC continues to be shielded beneath the convection.



Quoting hunkerdown:
I used to visit Barnegat Light on a weekly basis every summer from late 70s to mid 80s. Had friends there. Great fishing.
As it was once so eloquently put, "On the coast of New Jersey are some of the finest beaches to be found anywhere in the world. Here, on a narrow neck of land between the Atlantic Ocean and Barnegat Bay, is Seaside Heights, "The Town That Fun Built". I hope our beautiful beaches will not take the wrath of any of these brewing systems.
Quoting futuremet:


Preslord, I'm surprised you are not tracking this, since the Carolinas may be affected.

omg, now you have done it!
2603. cg2916
NEW BLOG!
Would not be surprised if we get a tropical depression out of the Bahamas blob this week.

97L might try something too.
San Juan radar doppler is the best source to follow the wave(97L) at this moment.
i am continuing to watch an area atn47w in association with a tropical wave. there is a very small and vigorous circulation within tnat wave near 8N 47W which is moving to the north of west. there is no convergence as yet but there is good divergence this is definitely a suspect area
big wow..
2608. cg2916
Guys, new blog!
COC about 60 miles south of PR,some thunderstorms approaching the coast,can see them from my house.
To me, it appears that the Bahamas AOI is growing larger, and trying to absorb everything around it, as it spits a tremendous amount of moisture northward, where itself could go in the future. It's bottom right section seems to be beckoning to 97l to join it, and 97L seems to be elongating towards the Bahamas AOI. I personally think, that 97L's trip over the Caribbean islands is a non-issue, whatever energy remains of it will be absorbed into the ever growing Bahamas AOI, which will be Ana. This is just my forecast, and I am self-taught. Please no one attack my theory too badly. If I'm wrong, I have no problem with being a horse's behind, lol!
2611. MahFL
Futuremet, please do more studying and use the correct terms.

""CDO" is an acronym that stands for "central dense overcast". This is the cirrus cloud shield that results from the thunderstorms in the eyewall of a tropical cyclone and its rainbands"

Blobs DO NOT have CDO's.

Thanks.
One more woman here in Dunedin, Florida.....just west of Tampa! Watching the tropics!
Quoting TampaSpin:
The energy from 97L will enhance the development in the the Bahamas......

Word, that's what I think too! Others may differ, but it's really, really o.k. to have divergent views. For all those who differ in opinion are respected just the same, at least by me!