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Tropical wave approaching the Caribbean a threat; Debby gets her name

By: Dr. Jeff Masters , 1:52 PM GMT on August 23, 2006

Forget about newly-named Tropical Storm Debby, now churning west-northwestward into oblivion in the open Atlantic. The area we need to focus on today is a tropical wave near 10N 53W, about 500 miles east of the southernmost Lesser Antilles Islands. This new wave is a threat to develop into a tropical depression later this week, once it crosses into the Caribbean. NHC has assigned this disturbance the name "Invest 97L", and has tentatively tasked the Hurricane Hunters to investigate it on Thursday afternoon.

While the wave does have the potential to eventually become a serious hurricane, it also has a number of hurdles to overcome, and it is more likely that it will never become a hurricane. Firstly, while satellite imagery does show some rotation at middle levels of the atmosphere, a pass by the QuikSCAT satellite at 5:11am EDT today showed no rotation at the surface, and just a slight wind shift. The system will have to develop a lot more spin, which will take time. There have been some intermittent bursts of heavy thunderstorm activity, which generated winds of up to 30 mph seen on the recent QuikSCAT pass, but the cloud pattern is very disorganized at present. Wind shear is favorable, a low 5-10 knots, but is a very high 30-40 knots just to the north, and any movement of this high shear zone to the south--or 97L to the north--might disrupt it. A large area of dry air and Saharan dust lies to the north, and this will interfere with development. The system should move through the Lesser Antilles Islands just north of the South American coast on Thursday and Friday, and this region of the Caribbean has been climatologically unfriendly to developing tropical storms. The presence of the South American land mass so close cuts off a key source of moisture for a developing storm, and many vigorous looking disturbances and tropical storms have died in the southeastern Caribbean.

The computer models forecast that wind shear over the south half of the Caribbean will remain low the rest of the week, so the further south 97L can stay, the more likely it is to develop. The 8pm EDT run of the GFDL last night did develop it into a tropical storm by tomorrow, but this model did a poor job with the track and took it too far north. The GFDL, UKMET, and NOGAPS models do not develop it. The Canadian model develops it early next week once it enters the central Caribbean south of Jamaica, and forecasts it will move into the Gulf of Mexico. If this system is going to develop, I suspect that the Canadian model has the right idea, and development will not occur until 97L reaches the central or western Caribbean.


Figure 1. Current satellite image of Invest 97L.


Figure 2. Preliminary model tracks for disturbance 97L approaching the Lesser Antilles Islands.

Debby
Tropical Storm Debby got a name last night, and is a modest 45-mph tropical storm headed west-northwest towards the north central Atlantic. Debby is expected to turn more northwestward over the weekend, and get pulled northwards and recurved into the prevailing westerly winds at high latitudes over cold waters early next week. Debby is not a threat to any land areas. The storm is in a moderately favorable environment for intensification, and could eventually make it to Category 1 hurricane status.

I'll have an update this afternoon.

Jeff Masters


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

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747. Wx35
11:18 PM GMT on August 23, 2006
man the waters in the GOM are really warm. If a storm gets in there it good get really ugly what do you think

http://wxmaps.org/pix/hurpot.html#ATL

depends on the upper level winds...I do not think heat content will be an issue. If it does make it..Notice the ULL to its north increasing the shear to its north. Will the ULL back off or does this pull a Chris....hmmmm

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8sht.html

Member Since: December 31, 1969 Posts: Comments:
746. TampaWeatherBuff
9:40 PM GMT on August 23, 2006

MEMORANDUM

FROM: Tampa, FL
TO: Wants-To-Be-Ernesto (AL97)
DATE: August 23, 2006

You are hereby formally invited to, and your services are solicited by, the fine city of Tampa, FL, which is badly in need of a nice power wash after this hot, humid summer so far.

Sincerely,

TampaWeatherBuff
a.k.a., "Cap'n Dan"
Member Since: December 31, 1969 Posts: Comments:
744. littlefish
8:59 PM GMT on August 23, 2006
97L doesn't look real healthy right now. But it looks healthier than Debby. Maybe it'll take a Dennis track?
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742. weathermanwannabe
8:44 PM GMT on August 23, 2006
It seems like 97L is starting to "thread through the eye of the needle" between land and the shear to the North...........Will it even make it through to the Gulf?
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741. melwerle
8:42 PM GMT on August 23, 2006
so just took a look at the weather.com map (btw - talking about pop-ups whenyou go to the site...ugh) - animated it and MAN OH MAN there is alot popping up all over the place...is that blob of storms off the florida coast just storms?
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739. littlefish
8:32 PM GMT on August 23, 2006
Uh-oh. 97L is getting really fat and is not nearly as tall as it was this morning and yesterday. Looking like a sandwich, not a doughnut... I want a nice round system. None of this flat squeezed-out crap.
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737. FierceWinds
8:27 PM GMT on August 23, 2006
1900hurricane at 8:23 PM GMT on August 23, 2006.
Yes, it appears Debbbie is weakining, but is it possible for Debbie to make it far west enough to make it a threat? The models don't think so.


Here's why:
Link
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735. melwerle
8:25 PM GMT on August 23, 2006
Hey Guys - so Debbie is off it's original track or still on track from before?
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734. 1900hurricane
8:23 PM GMT on August 23, 2006
Yes, it appears Debbbie is weakining, but is it possible for Debbie to make it far west enough to make it a threat? The models don't think so.

Link

Lank

Lonk

Note how the models that bring Debbie west also dissipate it.
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732. rwdobson
8:22 PM GMT on August 23, 2006
the big question could be, how far south does the East Coast trough go?
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730. rwdobson
8:21 PM GMT on August 23, 2006
sort of a cycle though, where if debby weakens and thus moves west, there's even more dry air/dust to deal with, leading to more weakening...
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729. IKE
8:21 PM GMT on August 23, 2006
"8-14 DAY OUTLOOK FOR AUG 31 - SEP 06, 2006: DURING WEEK 2... THE MODEL RUNS ARE CONTINUING THE GENERAL THEME OF A WEST COAST TROUGH - GREAT PLAINS RIDGE - AND EAST COAST TROUGH..."...that from the climate prediction center.
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728. Patrap
8:20 PM GMT on August 23, 2006
..once again.. Debbieforecast to be Low Cloud swirl offs Azores in 5-6 days...like in da creme soda"s demise...
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727. kmanislander
8:20 PM GMT on August 23, 2006
admittedly I am only an armchair wannabe when it comes to the tropics but I have followed the tropics for decades and if there is no low level circulation with 97L it is certainly one of the more robust systems I have ever seen without one
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726. Patrap
8:19 PM GMT on August 23, 2006
..can see Clint Eastwood as Philo Betto driving truck & saying.."Right Turn Debbie"!.....
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724. 1900hurricane
8:18 PM GMT on August 23, 2006
you can get 97L models here

Link
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723. Hardcoreweather
8:17 PM GMT on August 23, 2006
I thought Debby would be one to watch... apparently she's not much of a threat
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719. Canesinlowplaces
8:15 PM GMT on August 23, 2006
Hurricane 23, how do you surmise that the circulation is in the mid instead of lower. When I look at the rgb loop, if you had asked me, I would have said it's in the lower levels. What shows you its a mid level circulation?
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718. kmanislander
8:15 PM GMT on August 23, 2006
jp

wasnt that written hrs ago ?
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715. kmanislander
8:11 PM GMT on August 23, 2006
jp
why do you say that the circulation is at the mid levels ?
What about the low that is along the wave ?
Is that not at the surface and if so why is the circulation associated with the low not at the surface with it ?
Or are you saying there is no closed low ?

grateful for an explanation
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714. IKE
8:11 PM GMT on August 23, 2006
Posted By: GulfScotsman at 3:07 PM CDT on August 23, 2006.
Conditions at 41101 as of
1900 GMT on 08/23/2006:

Atmospheric Pressure (PRES): 1012.4 mb
Pressure Tendency (PTDY): -1.6 mb ( Falling )


That pressure is falling off....and that's over 100 miles North of 97L.
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712. rwdobson
8:08 PM GMT on August 23, 2006
Ok, so check out these long-range forecast maps showing the 500 mb heights. First, the 6-10 day map (Aug 29-Sept 2)

6-10 day

Note the ridge over Texas is continuous all the way across the Gulf and past Florida. With this pattern, any storm from 97L would be steered west into Mexico.

Now the 8-14 day...Link

Note how the ridge is split in two, and a trough (or at least a weakness) is there over Florida and the east coast. Under this situation, a storm could ride up over Florida and up the east coast...
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711. 1900hurricane
8:08 PM GMT on August 23, 2006
Hello
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710. hurricane23
8:08 PM GMT on August 23, 2006
right now the spin iam seeing with 97L looks like its not at the surface yet...It may very well work its way down to it in the next day or to as conditions appear pretty favorable for some slow development.
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709. vortextrance
8:08 PM GMT on August 23, 2006
I do still like the long term prospects of 97L over Debby.
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706. vortextrance
8:07 PM GMT on August 23, 2006
Posted By: jphurricane2006 at 7:58 PM GMT on August 23, 2006.
20kts of shear doesnt guarantee that a storm will not develop; also as 456 mentioned earlier; the shear is forecasted to lift out by later this week; the fact that it is further south gives 97L; through all odds a chance to develop before it reaches the islands


Didn't say 20knots of shear guarantees a storm can't develop.. I know what 456 has been saying, I have been saying the exact same thing about the shear since yesterday morning. It is possible it develops before the islands, just not likely imo.
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703. FierceWinds
8:06 PM GMT on August 23, 2006
hurricane23 at 8:02 PM GMT on August 23, 2006.
Guys right now what iam seeing with 97L is a circulation at the mid-levels, This afternoon it looks a little better organized and some slow intensification is possible as 97L will be moving over warm STT'S and a low shear environment...a track to the W -WNW is very possible in the next 2-3 days.


I concur and believe we're already starting to see a slight WNW movement.
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702. Chicklit
8:05 PM GMT on August 23, 2006
The lightening just struck so close that the hair on my arms went up and my lamp crackled!
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701. dnalia
8:05 PM GMT on August 23, 2006
Posted By: Zaphod at 3:02 PM EDT on August 23, 2006.
Really shouldn't Debby head for Dallas?


Would the headlines then say "Debby Does Dallas"?

Sorry.

So, is 97L going fooey or what? I'm getting conflicting reports.
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700. hurricane23
8:04 PM GMT on August 23, 2006
hlpisuzu there's no need to be rude jesus....my bad.
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699. hlpisuzu
8:03 PM GMT on August 23, 2006
Posted By: hurricane23 at 3:36 PM EDT on August 23, 2006.
Guys iam trying to figure out what the GFDL model is seein takeing 97L into the Southern bahamas?

Have you taken a look at the last time it was run? According to the graphic Dr. Masters posted in his blog, it hasnt been run since 8 PM LAST NIGHT...it doesnt take a rocket scientist to figure that one out...it hasnt run since...maybe that is why it "looks" like it is to far SE and off, however at 8 PM last night it was probably in the correct area...just my $0.02, now why it took it into the Bahamas on the run? I dont know...just looked at it, and it started the system off as a 51 knot TS...so disregard that 8 PM run...
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698. emagirl
8:02 PM GMT on August 23, 2006
no problem JP i am just at work so I read what I can.........I live on the COast and work EMA all the comments i get to read have been very interesting......thanks
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697. hurricane23
8:02 PM GMT on August 23, 2006
Guys right now what iam seeing with 97L is a circulation at the mid-levels, This afternoon it looks a little better organized and some slow intensification is possible as 97L will be moving over warm STT'S and a low shear environment...a track to the W -WNW is very possible in the next 2-3 days.

Here is a close up visible pic of 97L...



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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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