Caribbean disturbance 99L a dangerous rainfall threat for Haiti, Jamaica, and Cuba

By: Dr. Jeff Masters , 4:12 PM GMT on October 20, 2012

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A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that are beginning to show some organization, as seen on visible satellite loops. Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday, which will bring a multi-day period of heavy rains to Haiti, Jamaica, and eastern Cuba beginning on Sunday. The Dominican Republic may also see some heavy rains, though not as great. On Wednesday, a strong trough of low pressure will approaching the Eastern U.S., and the GFS and ECMWF models predict that this trough will turn 99L to the north, bringing the storm into the southeast Bahama Islands on Thursday or Friday. In their 8 am EDT tropical weather outlook, NHC gave 99L a 30% chance of developing into a tropical cyclone by Monday morning. I put these odds higher, at 40%. An Air Force hurricane hunter aircraft is scheduled to investigate 99L on Sunday afternoon.


Figure 1. Morning satellite image of Invest 99L.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 1000 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a modest amount of heavy thunderstorms, as seen on visible satellite images, and has gotten tangled up with an upper-level low pressure system. This upper-level low is pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a high 20 - 25 knots, but is forecast to drop to the moderate range, 10 - 20 knots, Sunday through Monday. This may allow for some slow development of 90L before it encounters very high wind shear of 20 - 40 knots on Tuesday and Wednesday. None of the reliable computer models develop 90L into a tropical cyclone. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 20% chance of developing into a tropical cyclone by Monday morning.

Jeff Masters

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Quoting GTcooliebai:
Grothar what do you think 99L could take a track similar to this storm or too far west?

Well, 99L is a bit further north than the 1932 hurricane was. But it's possible I suppose.
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753. 7544
hmm looks like we could 91L soon in the atl.

99l will be mystery strom for now on where it will go imo
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Quoting NCHurricane2009:

Look at the spin!


It is well-defined.
Member Since: July 21, 2011 Posts: 83 Comments: 7167
Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting Civicane49:
99L:


Look at the spin!
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Quoting NCHurricane2009:
If we get Sandy....this will be the 1st time I believe the Atlantic has had four consecutive years where we reach the 'S' storm. In other words...this would be the first time I know of that the Atlantic four years in a row produces 18 tropical storms each year (letter Q is skipped)...unbelievable!

I think part of this though is because storms like Patty or Oscar would have not been caught before the satellite era...and storms like Jose 2011 or Jerry 2007 would have not been classified before...


It would have to be 3 consecutive, 2009 had like 9 or 10 storms only.

'10 = Tomas
'11 = Sean (19th)
'12 = Possibly 99L

No hate, just bringing love.
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Quoting Grothar:


Ah, kids.
Grothar what do you think 99L could take a track similar to this storm or too far west?

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Quoting Grothar:
More models agreeing on intensity potential.




So ALL these models show 99L becoming a TS.

Or am I missing something?

Thanks Gro!
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99L:

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Member Since: July 17, 2009 Posts: 71 Comments: 27210

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Quoting NCHurricane2009:

And I didn't exist till 7 years after that...


Ah, kids.
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Quoting Grothar:



I wrote a few hours ago that the new models would probably show 99L moving over the far eastern end of Cuba. A few people agreed.


Ok. I missed that... Thx.
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If we get Sandy....this will be the 1st time I believe the Atlantic has had four consecutive years where we reach the 'S' storm. In other words...this would be the first time I know of that the Atlantic four years in a row produces 18 tropical storms each year (letter Q is skipped)...unbelievable!

I think part of this though is because storms like Patty or Oscar would have not been caught before the satellite era...and storms like Jose 2011 or Jerry 2007 would have not been classified before...
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Quoting Dakster:


Ok. I'll bite. What did you think?



I wrote a few hours ago that the new models would probably show 99L moving over the far eastern end of Cuba. A few people agreed.
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Quoting Grothar:
I think I will go horizontal soon. Have fun boys and girls.



Me too. Good night everyone.
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Blog update:

99L likely to develop over the Caribbean; 90L over the Atlantic
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I think I will go horizontal soon. Have fun boys and girls.

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Quoting Grothar:
Aha, just as I thought.


Yup, that is pretty close to where an area of jet fuel is. I pretty much agree with a track around that area currently. Hopefully there will be some shear that prevents this from really taking off. Right now I think a cat1 is likely for peak sometime in its life. That is my one moment of being serious for the hour.
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Quoting Grothar:


Oh, I know. just kidding back. The last time I can remember getting mad at anything was back in 1980 when they told me they weren't making bellbottom pants anymore.

And I didn't exist till 7 years after that...
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The next 3 names on the list: Sandy, Tony, and Valerie all end in the long -e sound.
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Quoting Grothar:
Aha, just as I thought.



Ok. I'll bite. What did you think?
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More models agreeing on intensity potential.

Member Since: July 17, 2009 Posts: 71 Comments: 27210
Quoting thunderbug91:
I've only got 360-something comments..... 3 jobs and full time school takes my life away.... :/
I need a storm to cancel school for a bit. I need a break..


If you are living in Jamaica or Cuba you may be in luck.
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Quoting NCHurricane2009:

I was just kidding....

And by the way...I've done just over 3000 comments and 236 blog entries since I started in Sept 2009....not sure what that makes me.....


Oh, I know. just kidding back. The last time I can remember getting mad at anything was back in 1980 when they told me they weren't making bellbottom pants anymore.
Member Since: July 17, 2009 Posts: 71 Comments: 27210
I've only got 360-something comments..... 3 jobs and full time school takes my life away.... :/
I need a storm to cancel school for a bit. I need a break..
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Aha, just as I thought.

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Quoting KoritheMan:

Taught you respect, have I?

You have taught me the opposite, jk. I have respect for people when it is due.
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Quoting washingtonian115:
Did that heavy rain event move over your area as well yesterday?.It was raining cats and dogs for a few minutes and then it went to moderate rain.

Yes, we got the whole shebang- rain, wind, and thunder. There was a tiny little shower earlier tonight but we could not have ordered a nicer day otherwise.
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Quoting Grothar:


It is beginning to get that round look to it. Not much convection but looking good.


We have all heard that before.... And then *poof*.....
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Quoting Grothar:


We're just filling in the time until the 11 PM comes out, which I am sure TA will post first. Look at it like a stage act. Before the star performer comes out, all these wannabe comedians have a lead in. It is almost a tradition now. We do the comedy relief until the action starts and then we go into "STORM MODE" and get serious.

I was just kidding....

And by the way...I've done just over 3000 comments and 236 blog entries since I started in Sept 2009....not sure what that makes me.....
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Quoting Grothar:


We're just filling in the time until the 11 PM comes out, which I am sure TA will post first. Look at it like a stage act. Before the star performer comes out, all these wannabe comedians have a lead in. It is almost a tradition now. We do the comedy relief until the action starts and then we go into "STORM MODE" and get serious.

Yo Gro, there aren't any active storms so I don't think there will be much to post at 11pm.
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Quoting reedzone:
The structure is excellent!


It is beginning to get that round look to it. Not much convection but looking good.
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Quoting wxchaser97:

Remember you are younger than he is, respect your elders, even though he can act like that...
Taught you respect, have I?
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Quoting TropicalAnalystwx13:

Such a kid..

Remember you are younger than he is, respect your elders, even though he can act like that...

I am currently working on a blog about 99L and 90L and I will have it out sometime tonight.
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Quoting CybrTeddy:
Wow, it feels nice outside! I think I might go for a race against a Prius. Last time I did it was a pretty close race, but I could only walk so fast.


I have always wanted to time one in the quarter mile, can you give me a minute so I can get my calendar.
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Quoting Grothar:


We're just filling in the time until the 11 PM comes out, which I am sure TA will post first. Look at it like a stage act. Before the star performer comes out, all these wannabe comedians have a lead in. It is almost a tradition now. We do the comedy relief until the action starts and then we go into "STORM MODE" and get serious.


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Quoting NCHurricane2009:
99-L needs to do something quick before more comments about racing Prius's....how many comments someone has made...or how old Gro & Patrap are...continue...


We're just filling in the time until the 11 PM comes out, which I am sure TA will post first. Look at it like a stage act. Before the star performer comes out, all these wannabe comedians have a lead in. It is almost a tradition now. We do the comedy relief until the action starts and then we go into "STORM MODE" and get serious.
Member Since: July 17, 2009 Posts: 71 Comments: 27210
Quoting reedzone:
The structure is excellent!

Damn. This is gonna be a beast.
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Quoting reedzone:
The structure is excellent!

Convection will increase tomorrow and I think we should have a TD in 24-36hrs.
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Quoting KoritheMan:


Nuh uh!

Such a kid..
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Quoting barbamz:


I really don't remember by myself, Gro (I was two or three years old back then, lol). But I've read about Surtsey in connection with the El Hierro stuff earlier this year (and this submarine volcano isn't done either, there is still some shaking in this region of the Canaries; I follow it occasionally).


Well, I am not going to say how old I was at the time, but it is a vague memory. :) We had been living in Iceland for just a short while before that in 1961.
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Quoting Grothar:


Only the last one. I'm not that old. But I do remember them being called the Hawaiian Island.


That's right Floodman was around when the dirt was new and Dino's roamed earth, you showed up after that. Sorry I get you two confused sometimes. You know how all old people look alike.
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Quoting KoritheMan:


Nuh uh!

Hey, hey ,hey, lets not fight here:)

Quoting KoritheMan:


Dammit Gro, stop pointing out my kindness. I'm supposed to appear cold-hearted!

Kori being cold-hearted, lol.
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99-L needs to do something quick before more comments about racing Prius's....how many comments someone has made...or how old Gro & Patrap are...continue...
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Quoting TropicalAnalystwx13:

Uhm, I'm pretty sure you started the insulting first several months ago, boy.


Nuh uh!
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Quoting Dakster:


What other funny things? ;)


Twit!
Member Since: July 17, 2009 Posts: 71 Comments: 27210
Quoting Grothar:


Who are you kidding, Kori. You would give him your left kidney if he needed it and you know it.


Dammit Gro, stop pointing out my kindness. I'm supposed to appear cold-hearted!
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Quoting Dakster:


Weren't you there when the Hawaiian islands formed too?


Only the last one. I'm not that old. But I do remember them being called the Hawaiian Island.
Member Since: July 17, 2009 Posts: 71 Comments: 27210

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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.

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