99L a heavy rainfall threat for Jamaica, Haiti, and Eastern Cuba

By: Dr. Jeff Masters , 2:35 PM GMT on October 21, 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 have a good degree of spin. These thunderstorms are beginning to organize into spiral bands, as seen on visible satellite loops. However, the amount of heavy thunderstorm activity is about the same as yesterday, and there are no signs of a surface circulation. An Air Force hurricane hunter aircraft is scheduled to investigate 99L this afternoon, but I expect this flight will be rescheduled for later.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
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. On Wednesday, a strong trough of low pressure to the north of 99L is expected to turn the storm to the north or north-northeast, which should put 99L in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. By Friday, 99L should be in the Central or Eastern Bahamas. It is unclear at this point whether or not the trough pulling 99L to the north will be strong enough to pull the storm all the way out to sea to the northeast; a narrow ridge of high pressure has the potential to build in over 99L late this week and force the storm west-northwest, with a potential threat to the western Bahamas and U.S. East Coast by next weekend. In their 8 am EDT tropical weather outlook, NHC gave 99L a 70% chance of developing into a tropical cyclone by Tuesday morning. 99L will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday through Wednesday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 830 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a small 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 providing 90L the spin it needs to become a tropical cyclone, but is also pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Tuesday. This may allow for some slow development of 90L before it encounters high wind shear of 20 - 30 knots on Tuesday night through Thursday. None of the reliable computer models develop 90L into a tropical cyclone, and it's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 30% chance of developing into a tropical cyclone by Tuesday morning.

The next name on the list of Atlantic tropical storms for 2012 is Sandy.

Jeff Masters

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I'm betting the graphic design team is busy over at the Weather Channel with the possible NE set up..Im sure brown and orange with be the color schemes in the DOOM captions to keep with Fall..
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Honestly I'm not that impressed with 99L right now. It's struggling for convection (probably at least in part due to DMIN though) and the overall structure looks the same as or worse than last night, much more like a t-wave than an organizing cyclone.



I also see the 18z GFS shifted east some. That seems like a pretty reasonable track to me, I think a grazing hit on S FL is possible but I'm not buying the idea of it coming up the East Coast yet, I say it gets pushed out to sea.
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569. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #1
TROPICAL DEPRESSION 25
9:00 AM JST October 22 2012
====================================

SUBJECT: Tropical Depression Near The Caroline Islands

At 0:00 AM UTC, Tropical Depression (1006 hPa) located at 9.2N 133.8E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving west slowly.

Dvorak Intensity: T2.0

Forecast and Intensity
========================

24 HRS: 10.2N 131.5E - 35 knots (CAT 1/Tropical Storm) Sea East Of The Philippines
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Quoting wxchaser97:

How was your swim meet today, sorry but I had to ask?
I volunteer to not send you to the NE. I'll just go myself and bring back video.

Or since I live in the NE i could do it for u..
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Off topic: So I was fortunate enough to see Jerry Springer hosting the Price Is Right live then to see a Jerry Seinfeld stand up show both for free these past two days and it was awesome...They were both in Atlantic city NJ..My point being if you like either of them and they come around go. They are funnier then you can imagaine in person. would have been well worth the price of admission..ok rant over haha
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Quoting NJcat3cane:
Mid-Atlantic/NorthEast hurricanes tend to hit in bunches over a course of a few years going back in history...We got one last year maybe we are entering a pattern where the Mid-Atlantic gets its share of tropical systemsfor the next decade or so/
This is what I've always thought as well. Good thing I kept all my hurricane prep supplies on hand!!
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Quoting TampaBayStormChaser:
I'm on Grand Cayman Island right now, and it has gotten breezy but nothing too bad. 

Hopefully it will stay that way!
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Quoting TomTaylor:
%uFFFDHowever, if we compare the surface level to the mid level it is clear that this system is not only heavily weighted to the NE in terms of convection and precipitation, but also severely vertically tilted -- if you can even call it that. The center of the mid level circulation is a few hundred miles to the NE of the surface low.

Doesn't look like a decoupling to me:




That's a side by side comparison of the lower troposphere (top image) and the upper troposphere (bottom image). It's very obvious where the circulation center is, and there is no apparent displacement. I don't see anything akin on satellite pictures either.

Now I'm not trying to downplay your analysis or anything. You are an excellent poster. I'm just not seeing your point this time.
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Talk about a model spread on 90l.

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Quoting NJcat3cane:
Mid-Atlantic/NorthEast hurricanes tend to hit in bunches over a course of a few years going back in history...We got one last year maybe we are entering a pattern where the Mid-Atlantic gets its share of tropical systemsfor the next decade or so/


With all the troughing we keep seeing, I wouldn't be surprised.
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Quoting Tropicsweatherpr:


That is good that they are on top of things. Keep us informed my friend.

Yeah, no problem.
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558. JRRP

Grecia y Turkia deberia tener cuidado con 90L
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Mid-Atlantic/NorthEast hurricanes tend to hit in bunches over a course of a few years going back in history...We got one last year maybe we are entering a pattern where the Mid-Atlantic gets its share of tropical systemsfor the next decade or so/
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Nice AC with 99L
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99L's pressure is down a millibar...

AL, 99, 2012102200, , BEST, 0, 146N, 777W, 25, 1005, DB, 34, NEQ, 0, 0, 0, 0, 1008, 180, 150, 0, 0, L, 0, , 0, 0, INVEST, S,
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Quoting nigel20:

Hey Tropics! Yes they are, this statement was released earlier today...

October 21, 2012 at 5 p.m.

*** INCREASED RAINFALL EXPECTED FOR THE BEGINNING OF THE WEEK……WITH POSSIBLE STORM CONDITIONS BY MID-WEEK
***


An Area of Low Pressure, with an associated Tropical Wave, is currently southeast of Jamaica and is generating unstable weather conditions over the island and its territorial waters. The System which is expected to be southwest of Jamaica on Tuesday, and move over the island on Wednesday, currently has a high chance of becoming a tropical cyclone during the next 48 hours The forecast is for occasionally heavy showers and thunderstorms to impact the island particularly during the afternoon on Monday. On Tuesday through Thursday expect an increase in rainfall with possible stormy weather conditions developing by Wednesday

Fishers and other marine interests, especially those on the cays and banks, are strongly advised to exercise caution as the system remains over the area. All interests are urged to pay special attention to subsequent news releases from the Meteorological Service

rlb


That is good that they are on top of things. Keep us informed my friend.
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18Z NAM (non-tropical model) hr 084 hr 84
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552. Gorty
Can't wait to see the 00z GFS run.
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just updated

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18Z NAM (non-tropical model) hr 072 hr 84
Member Since: July 15, 2006 Posts: 171 Comments: 53827
18Z NAM (non-tropical model) hr 060 hr 144
Member Since: July 15, 2006 Posts: 171 Comments: 53827
18Z NAM (non-tropical model) hr 048 hr 144
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Quoting KEEPEROFTHEGATE:
18Z NAM (non-tropical model) hr 024 hr 144

sandy does not show up on the map
oh,and i think ill be makin some tcrs till we have an actual storm to track
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18Z NAM (non-tropical model) hr 036 hr 84
Member Since: July 15, 2006 Posts: 171 Comments: 53827
Quoting nigel20:

Hey Tropics! Yes they are, this statement was released earlier today...

October 21, 2012 at 5 p.m.

*** INCREASED RAINFALL EXPECTED FOR THE BEGINNING OF THE WEEK……WITH POSSIBLE STORM CONDITIONS BY MID-WEEK
***


An Area of Low Pressure, with an associated Tropical Wave, is currently southeast of Jamaica and is generating unstable weather conditions over the island and its territorial waters. The System which is expected to be southwest of Jamaica on Tuesday, and move over the island on Wednesday, currently has a high chance of becoming a tropical cyclone during the next 48 hours The forecast is for occasionally heavy showers and thunderstorms to impact the island particularly during the afternoon on Monday. On Tuesday through Thursday expect an increase in rainfall with possible stormy weather conditions developing by Wednesday

Fishers and other marine interests, especially those on the cays and banks, are strongly advised to exercise caution as the system remains over the area. All interests are urged to pay special attention to subsequent news releases from the Meteorological Service

rlb

intresting
well,models are putting 99l to our east
YAY:)
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18Z NAM (non-tropical model) hr 024 hr 84
Member Since: July 15, 2006 Posts: 171 Comments: 53827
18Z NAM (non-tropical model) hr 012 hr 84
Member Since: July 15, 2006 Posts: 171 Comments: 53827
542. beell
Quoting TomTaylor:
Well that is expected, the system hasn't really had a chance to develop yet. Mid level circulation has been lagging behind the surface circulation off to the east. This can be seen on CIMSS imagery and satellite imagery.

I'm fine with the classification as a monsoon depression. I don't understand how that directly relates to the storm being pulled out of the Caribbean, however.


Top to bottom.
850, 700, 500mb relative vorticity.





Seems somewhat "stacked" on the CIMSS products.

And in my fantasy world, a surface center would make a cylonic loop around the larger low covering the entire Caribbean and begin a northward track-with the monsoon-like depression lifting out to the NE-still trying to coalesce a well defined surface center somewhere in the middle of the broader low. The broad low following the path of least resistance as you have described after 72-96 hrs.
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Quoting GeorgiaStormz:


No I wasn't going to do much better anyway, we arent trained for that right now, its more for evaluation at this point. :)

Yeah... sure... right...
Quoting TropicalAnalystwx13:
Convection continues to fire with 90L although it is not particularly deep in nature.


It is an improvement and 90L is looking better. I believe this has a decent chance to develop into Sandy or Tony.
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Quoting Tropicsweatherpr:
Hi nigel. Are the authorities there talking about this system there and about preparations?

Hey Tropics! Yes they are, this statement was released earlier today...

October 21, 2012 at 5 p.m.

*** INCREASED RAINFALL EXPECTED FOR THE BEGINNING OF THE WEEK……WITH POSSIBLE STORM CONDITIONS BY MID-WEEK
***


An Area of Low Pressure, with an associated Tropical Wave, is currently southeast of Jamaica and is generating unstable weather conditions over the island and its territorial waters. The System which is expected to be southwest of Jamaica on Tuesday, and move over the island on Wednesday, currently has a high chance of becoming a tropical cyclone during the next 48 hours The forecast is for occasionally heavy showers and thunderstorms to impact the island particularly during the afternoon on Monday. On Tuesday through Thursday expect an increase in rainfall with possible stormy weather conditions developing by Wednesday

Fishers and other marine interests, especially those on the cays and banks, are strongly advised to exercise caution as the system remains over the area. All interests are urged to pay special attention to subsequent news releases from the Meteorological Service

rlb
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539. 7544
Quoting TropicsGirl:
I've been reading about the possible scenarios today - what are the chances that 99L follows a path similar to Wilma? Is that possibility even in the cards?


normally this time of the year they do but this ones going to head north maybe more like a fay track imo or make a left turn briefly just off of se fla imho
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Quoting wxchaser97:

Nah, I'm good going by myself.
So in short you didn't do good and you are trying to make yourself feel better.


?


No I wasn't going to do much better anyway, we arent trained for that right now, its more for evaluation at this point. :)
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537. JLPR2
Quoting TropicalAnalystwx13:
Convection continues to fire with 90L although it is not particularly deep in nature.



Probably due to the weak ULL just to the NE of it.

But D-max could give it a push, come on 90L!
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99L
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Hi nigel. Are the authorities there talking about this system and about preparations?
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I would be getting my stuff in order if I lived in the Cayman Islands...

While I don't think it will be a major Hurricane event, it could get a little nasty for them.
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Quoting GeoffreyWPB:
Very nice Tropical Tidbit Levi...

Levi's Tropical Tidbit

Thanks for sharing, Geoffrey! :)
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WTNT21 KNGU 211530
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE
WITHIN 100 NM EITHER SIDE OF A LINE FROM 14.8N 76.0W TO 14.8N 78.9W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 211200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 14.7N 75.5W. THE SYSTEM IS MOVING WESTWARD AT 07 KNOTS.
2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING INTENSIFICATION OF
A TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA. AT 211200Z,
SATELLITE IMAGERY INDICATED AN AREA OF INCREASED THUNDERSTORM ACTIVITY
THAT HAS PERSISTED OVER THE LAST 24 HOURS. WARM SEA SURFACE TEMPERATURES
OF 83 TO 85 DEGREES FAHRENHEIT IN CONJUNCTION WITH A FAVORABLE UPPER AIR
ENVIRONMENT MAY ENHANCE DEVELOPMENT OF THIS SYSTEM INTO A TROPICAL CYCLONE.
3. THIS ALERT WILL BE UPGRADED TO WARNING OR REISSUED AS REQUIRED
BY 221530Z.//
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Quoting Tropicsweatherpr:


Good analysis there. But why NHC keeps saying that enviromental conditions will be favorable?
Same thing happens when Rafael was developing,was moving NNW, approaching the island of Vieques but al the thunder storms were to its NE, in a few hours the center relocated under the thunders storms 80miles to the NE, by St. Martin, ending the threat to Vieques, PUerto Rico, and all the warnings as well...
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Quoting TropicsGirl:
I've been reading about the possible scenarios today - what are the chances that 99L follows a path similar to Wilma? Is that possibility even in the cards?

No because the environment won't allow 99L to get too far west.
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Quoting TropicsGirl:
I've been reading about the possible scenarios today - what are the chances that 99L follows a path similar to Wilma? Is that possibility even in the cards?

No.
Member Since: July 6, 2010 Posts: 113 Comments: 32033
Convection continues to fire with 90L although it is not particularly deep in nature.

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Quoting TropicsGirl:
I've been reading about the possible scenarios today - what are the chances that 99L follows a path similar to Wilma? Is that possibility even in the cards?


No.
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I've been reading about the possible scenarios today - what are the chances that 99L follows a path similar to Wilma? Is that possibility even in the cards?
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Quoting Tropicsweatherpr:


Good analysis there. But why NHC keeps saying that enviromental conditions will be favorable?
Conditions will be favorable for gradual development. The storm wont have a chance for more significant development until it exits the Caribbean, however.
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Good evening fellow bloggers!
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Quoting beell:


Having a little trouble finding an actual mid-level center a few hundred miles to the NE of any surface center at the present time.

Your explanation is similar to Levi's and is a workable mechanism at some point. I'll take my monsoon depression scenario and go home now, lol.
(j/k)

And thank you for the detailed response.
Well that is expected, the system hasn't really had a chance to develop yet. Mid level circulation has been lagging behind the surface circulation off to the east. This can be seen on CIMSS imagery and satellite imagery.

I'm fine with the classification as a monsoon depression. I don't understand how that directly relates to the storm being pulled out of the Caribbean, however.
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Quoting Neapolitan:
It was very hot in parts of the nation's midsection today, primarily Oklahoma, which saw a number of record high temps in the mid 90s. That'll be short-lived, however, as the CPC is now calling for some pretty cold weather for a huge chunk of the U.S. centered around the lower Mississippi Valley in the 6-10 day period. The West Coast and the extreme Northeast will remain toasty, but, still, next week's setup looks very fall-like...

cold

The 8-14 day outlook shifts the cold weather to the east some while the warm temps come further east too. Half the country would still remain in a welcomed fall pattern while others are pretty warm. The eastern 1/3 of the country would remain wet while the other 2/3 are average to below average, besides the Pacific NW.
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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.