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Distubance approaching the Caribbean grows stronger

By: Dr. Jeff Masters , 8:21 PM GMT on August 23, 2006

A tropical wave near 11N 55W, about 400 miles east of the southernmost Lesser Antilles Islands, is moving westward towards the Caribbean at about 20 mph. Thunderstorm activity has increased markedly today in association with this wave (labeled 97L by NHC), and it has the potential to develop into a tropical depression by Thursday. The Hurricane Hunters are tasked to investigate it on Thursday afternoon. The thunderstorm activity is still pretty disorganized, and mostly lies to the west of the center of circulation, so noon Thursday is the earliest it is likely to reach tropical depression status.

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 has slowed development today. The storm will spread heavy rains and wind gusts to 40 mph across Trinidad, Tobago, Grenada, and the South American coast of Venezuela on Thursday, and the ABC Islands of Aruba, Bonaire, and Curacao on Friday. Development into a tropical depression--or a tropical storm--is highly dependent on how close 97L comes to the coast of Venezuela. The southeast Caribbean off the Venezuelan coast 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 here.

The computer models' take on things
The latest 8am EDT computer model runs are in. The Canadian model continues to be gung-ho, developing 97L into a strong tropical storm on Saturday, south of Jamaica. The NOGAPS model assumes a more southerly track will occur, and develops 97L Saturday once it moves off the coast of Columbia. NOGAPS then takes a weak storm along the north coast of Honduras, then across the Yucatan and into the Gulf of Mexico. The GFS assumes the storm will move further north than is reasonable, and does not develop it. I think the GFS solution can be discounted. The UKMET takes the storm along the north coast of South America, and does not develop it.

My take on things
I believe there's about a 60% chance 97L will become a tropical storm. It should come very close to developing into a tropical depression Thursday afternoon or evening. However, its close proximity to South America will probably keep it somewhere between a near-tropical depression and a 45-mph tropical storm until Saturday. If it survives into Saturday, intensification into a strong tropical storm or hurricane in the western Caribbean is possible. There may be additional obstacles to overcome by then--such as too much wind shear, or the Yucatan Peninsula or Honduras getting in its way.


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 has deteriorated a bit this afternoon, thanks to dry air and cooler waters. 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 will be in a more favorable environment for intensification on Friday, and could eventually make it to Category 2 hurricane status, as predicted by the GFDL model.

I'll have an update Thursday morning.

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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1834. AllyBama
1:33 PM GMT on August 24, 2006
Good morning everyone and greetings from wonderful Mobile!
Member Since: December 31, 1969 Posts: Comments:
1833. Zaphod
1:31 PM GMT on August 24, 2006
Amateur question here......

I have watched long enough to understand the general biases of the models, and to learn that most do not accurately predict path until a system has existed for a day or two. None seem very good at predicting cyclogenesis.

Are there any models which focus solely on cyclogenesis, and do not worry about future intensity and track? It would seem that accurate prediction of deep convection and localized interactions that affect development of closed circulation at the surface would be valuable, and could then better seed the existing models. It seems like "we" have pretty good ideas of where to look, but we have to wait until a circulation pops out to say much.

Zap
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1832. Cavin Rawlins
1:30 PM GMT on August 24, 2006
new blog is up
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1831. nash28
1:30 PM GMT on August 24, 2006
I think we're all gonna go batty right now with these models. The fact that the GFDL went from CAT2 to dissipation shows us the models are having fits right now trying to initialize this. It will take several more runs before they start getting a grip.
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1829. Tazmanian
1:28 PM GMT on August 24, 2006
: Weather456 ok what wait and see
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1828. Tazmanian
1:27 PM GMT on August 24, 2006
Ill pick...door number 2....arhhhh run for yer lives

now that funny sorry could not help it
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1827. guygee
1:26 PM GMT on August 24, 2006
Posted By: Weather456 at 11:55 AM GMT on August 24, 2006.
guygee, that was from yesterday.....SLU posted a pick just like that last night....and 97L is already near Barbados and that pass shows where it was last night.

Weather456 - Your are correct. The same link now shows at the top 12:07 UTC, but the actual data is unchanged. I finally figured out it is the small number below the image in violet that shows the time of the swath intersect with 20N.

For example, all of these links show identical data, collected at 21:42 August 23, even though the time labels at the top of the image are all different:
06082401ds
06082402ds
06082403ds
06082404ds
06082407ds
06082408ds
06082409ds
06082412ds

So that is a nice insight into interpreting the QuicSCAT data to get the correct times. Good to learn something new today.
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1824. Cavin Rawlins
1:25 PM GMT on August 24, 2006
Taz, my estimated intensity might be higher at 11:30am
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1822. Tazmanian
1:25 PM GMT on August 24, 2006
that is a pin hole eye look how small it is wow that has too be a cat 5 now if not 155mph cat 4 hurricane

lol
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1820. vortextrance
1:24 PM GMT on August 24, 2006
and there is also the possibility (large) that i don't know what the hades i am talking about! LOL

LOL Thelmores, I think that goes for all of us.
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1819. littlefish
1:24 PM GMT on August 24, 2006
There's some dry air creeping around 97L to north and even west a bit. But new flare ups are starting to show. Looks like strong shear ahead to the west. Dry air and shear. Let's see if this system can dodge those 2 bullets this time and be our 1st hurricane (unless Debby intensifies). Wonder if the shear in E caribb will dissipate in time.
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1817. whirlwind
1:22 PM GMT on August 24, 2006
Either one would be interesting:







Ill pick...door number 2....arhhhh run for yer lives
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1816. Tazmanian
1:21 PM GMT on August 24, 2006
Hurricane IOKE



--------------------------------------------------------------------------------
UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 7.1
Tropical Cyclone Intensity Estimation Algorithm
Disclaimer | Method Description and Validation | Sponsors



Current Intensity Analysis

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT - Version 7.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 24 AUG 2006 Time : 123000 UTC
Lat : 18:45:56 N Lon : 172:42:24 W


CI# /Pressure/ Vmax
6.5 / 936.7mb/127.0kt


6hr-Avg T# 3hr-Avg T# Adj T# Raw T#
6.5 6.5 6.6 6.6
Latitude bias adjustment to MSLP : +1.7mb

Estimated radius of max. wind based on IR :N/A km

Center Temp : -9.1C Cloud Region Temp : -71.8C
Scene Type : EYE


by looking at this it look more like a cat 5 storm then a cat 4 too me dont you?
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1815. Cavin Rawlins
1:20 PM GMT on August 24, 2006
thanks StormW,

Taz, might be at 11am
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1814. thelmores
1:18 PM GMT on August 24, 2006
ok, been studying 97L, and here is my take.....

we could end up with nothing, or possible "2" storms from 97L......

i can see where the southern component of 97l skirts the SA coast, emerges west.....

the northern portion could take a more wnw track.....

ok, seems unlikely to me that we will get "2" storms, but at this point, i couldnt tell you which part, upper or lower, will prevail, if at all.....

if i had to guess..... the lower portin may fizzle somewhat due to interaction with SA, which allows the upper portion to be more free of the interaction with the southern portion, which to me at this point, seems to be inhibiting the upper portions development.

i think he "upper" portion could have a shot at the east coast....

this is not wishcasting, just trying to throw out possibilities.....


and there is also the possibility (large) that i don't know what the hades i am talking about! LOL
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1812. Tazmanian
1:18 PM GMT on August 24, 2006
so weather456 is it back to cat 4?
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1811. PBG00
1:18 PM GMT on August 24, 2006
Don't put too much stock in the canadian..very aggresive in intensity.Too aggresive
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1810. Cavin Rawlins
1:15 PM GMT on August 24, 2006
.01CIOKE.115kts-945mb-186N-1725W.99pc.jpg

Its going into the WPAC in 8 degrees longitude...

So it might be renamed
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1808. jandree22
1:14 PM GMT on August 24, 2006
Excuse my ignorance, bu which model on the map represents the 'Canadian' model that several seem to be confiding in? A line color or abbreviation would really help ;-)
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1807. Tazmanian
1:13 PM GMT on August 24, 2006
Weather456 yes the navy site has her at 115kt and 945mb but it may be a lot stonger then that
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1806. Cavin Rawlins
1:12 PM GMT on August 24, 2006
Taz, i see it, how much 115knots
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1805. Tazmanian
1:10 PM GMT on August 24, 2006
hey weather456 look at this

24/1200 UTC 18.6N 172.5W T6.0/6.0 IOKE


this storm is going nuts now the navy site has it at 115kt and 945mb but it looks a lot stoger thne that now oh did you see my photo


pin hole eye


hey weather456 is that a pin hole eye?
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1804. ricderr
1:10 PM GMT on August 24, 2006
Posted By: WeatherByrd at 12:58 PM GMT on August 24, 2006.
Is it me or does little Debbie look like she is almost dead?

just you
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1803. Cavin Rawlins
1:06 PM GMT on August 24, 2006
Taz, i wouldnt call it a pin-hole eye
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1802. vortextrance
1:06 PM GMT on August 24, 2006
Don't bring that one up Gulf. If you thought there was panic on here yesterday.LOL
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1800. whirlwind
1:05 PM GMT on August 24, 2006
F Debby she aint gonna hit land.


97 has been a sleeper all along. quietly crossing the Atlantic while we were hoping for Debby to come here. Now it will sleep and later rapidintensify!!
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1798. WeatherByrd
1:03 PM GMT on August 24, 2006
Is it me or does little Debbie look like she is almost dead?
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1797. Cavin Rawlins
1:02 PM GMT on August 24, 2006
Ioke Intensity at 8:00amEDT

Curved Band Pattern/Cloud Pattern
0.3 Spiral - DT 1.5

Shear Pattern
None - 0.00

CDO
-CDO Central Feature

1 1/4 degrees latitude- DT 2.1

-CDO Banding Features

Modest - DT 1

Eye Feature/Pattern
Well Define - 0.8

Further Considerations (environmental factors)
CDO Cloud Temperature (.2)

Ioke T Number is 1.3+2.1+1+0.2+0.8=5.4

5.4 is 117mph, 960mbar MCP/Category Three Hurricane
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1796. TampaWeatherBuff
1:02 PM GMT on August 24, 2006
Wants-to-Be-Ernesto may not make it into the Carribean, much less the GOM.
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1795. whirlwind
1:02 PM GMT on August 24, 2006
97 is doing just what some models forecast. going little south to avoid shear and reimerging and going north then
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1794. IKE
1:02 PM GMT on August 24, 2006
Posted By: whirlwind at 8:01 AM CDT on August 24, 2006.
morning-


Posted By: IKE at 7:57 AM CDT on August 24, 2006.
It's getting sheared.

Maybe it will kill it.

ARRHHHH! Are you crazy?? What will then happen to the gulf cane then..?? chezzz


Then there's no gulf cane...which is great news.
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1792. vortextrance
1:01 PM GMT on August 24, 2006
I really think the NHC is being so bullish about development today, because they want the news people to start paying attention. Which I have no problem with. As far as for the shear it is weakening some and should continue to do so. I don't think 97L will dissipate but it will be setback.
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1791. Tazmanian
1:01 PM GMT on August 24, 2006
is that a pin hole eye?
lol
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1790. weathermanwannabe
1:01 PM GMT on August 24, 2006
BTW..That trough coming through the Northern Gulf is beginning to eat into the UUL in the Gulf..........It may be history by this time tommorow...............Im also off to work and will check back this afternoon......
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1789. whirlwind
1:01 PM GMT on August 24, 2006
morning-


Posted By: IKE at 7:57 AM CDT on August 24, 2006.
It's getting sheared.

Maybe it will kill it.


ARRHHHH! Are you crazy?? What will then happen to the gulf cane then..?? chezzz
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1787. Tazmanian
12:58 PM GMT on August 24, 2006
hey it look like the photo of weather456 has on ioke it looks like to me it may have a pin hole eye



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1786. IKE
12:57 PM GMT on August 24, 2006
It's getting sheared.

Maybe it will kill it.
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1785. Canesinlowplaces
12:56 PM GMT on August 24, 2006
It seems the difference between 97l and most of the other Atlantic systems that died so far this year is that it has a lot of moisture to build convection with. That may be enough to keep it alive through the shear over the next 24 hours or so. Chris didn't have that moisture and just dissipated when shear increased. I agree today will tell a lot of the story on what will happen. The NHC is certainly leaning toward some developement.
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1784. Tazmanian
12:55 PM GMT on August 24, 2006
Link


weather456 if you look at this loop it seen to me it is now try to make some kind of a trun but i cant tell
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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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